I built my first electronic DIY kit when I was about 10 years old. Dad brought home the Radio Shack One-Tube AM receiver P-Box kit and we spent the better half of the following Saturday at the workbench in the basement building it together.
It was an amazing formative experience – spending the day working on the project with dad, learning about the various electronic components and how they worked in the circuit, and getting my first try at soldering.
I treasured the completed radio and can vividly recall that magic moment when I first clipped the ground wire to an exposed gas pipe behind the parlor stove, sticking the hard plastic crystal earpiece in my ear and tuning the loopstick and hearing WBZ in Boston coming in loud and clear on the radio dad and I built out of a handful of parts.
This was the first of many Scie`nce Fair™ P-Box kits I would build throughout my early teen years. No Christmas or birthday was complete without one (or two!) new kits. I remember building the organ, the two-transistor AM radio, the “GoofyLight,” the indoor/outdoor electronic thermometer, the moisture detector, the AM Wireless microphone and the frequency standard.
I was hooked on kit-building and at some point, in my teen years I saw my first Heathkit catalog and was blown away at the more complex scale and wide variety of Heathkits… radios, hi-fi gear, test equipment, computers, even television sets. I began setting my sights on taking my kit-building to the next level.
However, in the mid- to late- eighties my focus and all of my earnings went into getting through college. By the time I had the time and disposable income to return to the kit-building workbench, the Heathkit era was sadly over.
At the turn of the century, I was in the position to have the time and money to return to my radio and electronics hobby. In 2002 I earned my amateur radio license and from the get-go started building ham-radio related kits. These included receivers and QRP transmitters and a variety of accessories like tuners, station clocks, sold by kitters such as Oak Hills Research, Four State QRP Group, MFJ, Small Wonders Lab, TenTec, and Rex Harper (QRPMe), among others. These were fun builds and there is nothing like using gear you built to make contacts on the air.
However, even the best ham gear I built still fell short of having built and having a showpiece full feature 100-watt multi-mode transceiver like the venerable HW101 in my shack.
In 1998, Elecraft, a new retailer of amateur radio gear was founded in California by Wayne Burdick and Eric Swartz with the introduction of their first product, the K2, an HF transceiver that could be purchased as a kit or fully assembled.
The K2 features dual VFOs with multiple memories, split TX/RX operation, RIT/XIT, full break-in CW, memory keyer, narrow IF crystal filtering, and IF derived AGC and the base radio can be built as a 5-watt QRP CW rig with optional accessory boards available to add SSB and amplify the RF output to a full 100 watts.
Initial reviews by the ARRL and other professional publications as well as those written by amateurs who have built and operated the K2 were excellent. The consensus was that the K2 has become a worthy choice for builders lamenting the disappearance of Heathkit. Reviews cited that the Elecraft kits were well packaged, completed, and the instruction manuals and documentation provided was detailed and easy to follow – not unlike the Heathkit manuals of a prior generation. Elecraft also got high points in published reviews for excellent customer support.
A bit over two years ago, my wife Ellen gave me the K2 kit, along with the 100 watt amplifier board and the SSB board as a gift for our tenth wedding anniversary. (I frequently point out that no man ever married better than I!)
Although I wanted to build the K2, and indeed put it on my gift ‘wish list’ – I let it sit in the workshop for over two years! I knew the project would take months on end to complete, and in order to succeed I would need to maintain a clean workspace, take my time and work slowly and diligently.
I think I have many fine qualities, but I’d be the first to tell you attention to detail and neatness are not among them. I was further intimidated by the fact that electronic components have gotten smaller while I have gotten older. My vision, which was always poor from birth, wasn’t getting better and my hands are starting to get a little shaky.
I finally resolved as we headed towards 2022 to tackle the K2. I created a new ‘protected’ workspace in my shack/mancave, moving in a folding banquet table, topping it with a pair of self-healing cutting mats and setting up my magnifier lens, solder station, some essential hand tools and my VOM, capacitance/inductance meter and my laptop.
The bigger resolution was to keep this space protected and clean. I resolved to not let this space become cluttered. I would not place anything not Elecraft related on this dedicated workspace, and I also resolved to clean up the space every time I stopped work, making sure I didn’t leave any loose parts out.
And with all that in mind, I finally started my build this month and my intent is to blog about the experience here and intend to blog as I complete each board. I invite you to join me for the journey. I hope those who have already built the K2 reach out with comments, tips and tricks – any input will be most appreciated. I also hope that this blog may be a resource or an inspiration for other builders.
Build this low power dirty AM transmitter and learn about RF modulation.
In the 21st century we have all become accustomed to our connected high-tech lifestyle and we more or less take our internet based social and commercial connectivity for granted until the ‘network goes down.’ Much of the technology that drives our digital being are computer based, but another essential element is radio technology, without which we would find ourselves much less connected.
How does ‘radio’ work?
Long before manipulated radio waves were used to provide the backbone of today’s digital cellular and cloud based information network, those of us who grew up in the twentieth century knew radio primarily as a means to enjoy music, news and talk, via the AM and FM radios in our homes and cars. But what is radio?
Simply put, radio is the transmission and reception of electromagnetic waves that are encoded with data. The data could be spoken word, music, or digital data like text and email messages or larger digital files like software or other data files.
The data that can be transmitted via radio waves exists as low-energy signals and they must be attached to a high-energy signal called a carrier wave in order to be transmitted. A carrier wave is at a significantly higher frequency than the input signal and is typically sinusoidal.
The mixing of the signal with the carrier wave is a process called modulation. There are several ways a carrier can be modulated, the two most common modes of modulation for an audio signal is amplitude modulaion (AM) and frequency modulation (FM). (Another common method of modulation a carrier signal that is beyond the scope of this article is phase modulation (PM)).
Amplitude modulation involves varying the signal strength, or amplitude, of the carrier wave in direct proportion to the message signal. Frequency modulation involves varying the frequency of the carrier wave in dirrect proportion of the message signal.
A simple low power AM radio transmitter
It is possible to construct a very simple low power transmitter built around the ubiquitous 555 Time Integrated Circuit which is capable of demonstrating the principle of amplitude modulation by mixing an audio signal with a carrier signal that can be transmitted to and received by a AM radio receiver.
The 555 timer chip was designed in 1971 by Hans Camenzind and has remained one of the most popular and versatile integrated circuit chips ever produced. Simple when compared to today’s chips which may contain tens of billions of transistors, the 555 has 25 bipoloar transistors, 15 resistors and 2 diodes.
The 555 chip has three distinct modes of operation – monostable, bistable, and astable.
The monostable mode is also known as the one-shot mode and will output a single pulse of current for a specified length of time. The bistable mode is also known as the flip-flop mode and alternates between two stable states, on and off, controlled by the trigger and reset pin.
The astable mode is also known as the oscillator mode and can be used to generate a carrier wave that could be modulated in a model RF transmitter circuit. We will employ this feature of the 555 chip for our transmitter circuit described below.
Traditionally the carrier wave in a radio transmitter is a continuous sinusoidal wave. However, the 555’s output is digital, either on or off, so the resulting wave is a square wave. An alterenating current sine wave is smooth and continuous and is optimal for carrying an information signal, but the square wave will work for our purposes.
I will now present and describe a simple AM radio transmitter circuit that you may wish to construct to observe and demonstrate radio modulation. This circuit design can be found on hundreds of websites oftentimes with small variations component value changes or minor modificaitons to the basic circuit. The circuit I present here is based on the core circuit, nominally modified to reflect what I have found to work well on my bench. I encourage readers who take the time to build my circuit to experiment and share modifications letting us know how you may have enhanced performance.
We will start by looking at the transmitter circuit by its three sub-circuits. The first is the oscillator circuit that produces the carrier wave, the second is the audio input sub-circuit, and thirdly we add the output amplifier and antenna.
1.) The Oscillator
The schematic diagram below is built upon the basic 555 astable circuit and this is the heart of the transmitter. The frequency of the carrier wave output on pin 3 is controlled by how rapidly capacitor C1 charges and discharges. The values of resistors R1, R3 and R4 will determine how quickly C1 charges.
When the charge of C1 reaches 2/3 of the control voltage Vcc, the output at pin 3 goes high. When the charge of C1 discharges to 1/3 of Vcc, the output at pin 3 goes low. Changing the resistance of the RC circuit by adjusting R4 will inversely change the output signal frequency. Increasing R4 will decrease the frequency and decreasing R4 will increase the frequency.
2. Audio Input
When a low energy audio signal is injected at the control pin, pin 5, the 555 will mix the input signal with the signal of the carrier wave and produce an amplitude modulated output signal at pin 3, output.
It is important to note that because the carrier wave generated by the 555 oscillator circuit is a digital pulse wave, where the output goes from completely on to completely off, the modulation of the carrier isn’t pure amplitude modulation, but pulse amplitude modulaton.
The pulse modulated RF signal will not be able to capture all of the fine detail of the input signal and you will notice that as a result, that the sound coming from the receiver speaker will sound a bit choppy and not as pure as you are accustomed to.
3. RF Amplification and Signal Output
The modulated RF signal is output at pin 3 of the 555. Attaching a simple piece of wire to pin 3 will serve as a crude antenna causing the modulated signal to be transmitted, or radiated into space where it can be picked up by properly tuned radio receivers.
Because this is an exteremely low power transmitter, I have added a single NPN bipolar junction transmitter (2N3904) at pin 3 to perform as an amplifier to boost the output signal strength. The base of the transistor is connected to output pin no. 3 of the 555 and the antenna wire will be connected to the transistor emitter. Power is supplied to the transistor via the collector.
An ideal length for the transmitting element for a radio antenna is 1/4 of the signal wavelength. This length gives us an efficient antenna length where the signal will resonate with minimal loss of signal. What would that length be for this transmitter?
Radio wavelength is calculated as the speed of light, (the speed at which RF waves also travel,) expressed in meters per second divided by frequency expressed in Hertz. The speed of light is 299,792,458 meters / second and the frequency range of the standard AM broadcast band in North America is 550 – 1700 KHz. Doing the math we learn that the broadcast band wavelength ranges from 176.3 meters to 545.1 meters.
Dividing these figures by four, we calculate the optimal antenna length for our transmitter would need to be between 44 and 136 meters or 144.36 to 446.19 feet! Constructing such an antenna for a simple circuit would be impractical and costly.
In this build we are using a piece of wire that is approximately one meter or a bit over 39 inches long. Because such a short antenna length is non-resonant and because the transmitter signal output is very week, you will find draping your antenna wire over the radio receiver establishing a loose coupling to the receiver will give you best results.
If you decide to build this circuit you may wish to experiment with different antenna designs to see how the may affect the range of your output signal. You may try a longer wire and another website suggests using a(n empty) beer can as an antenna.
Ham radio operators often make use of coils when antenna space is limited. Adding a tightly wound wire coil will add inductance allowing a physically shortened loaded antenna become more resonant at a longer wavelength. The concept of designing inductance loaded antennas is a concept goes beyond the scope of this article, but there is no shortage of excellent websites available that cover this topic if you are curious and know how to use the Google.
Using the transmitter
Once you have built the transmitter circuit, using it is straightforward and should be fairly intuitive. In addition to connecting the antenna wire to the transistor emitter and draping it over the receiver, you will of course need to supply a control voltage and an audio signal.
I have found that a 9 volt battery works well with this simple circuit as it is compact and will provide plenty of current to drive the circuit. The 555 will work with a Vcc ranging from 5 to about 15 volts giving you plenty of options.
For my audio source, I initially used the audio output from my laptop but have found that using my Activo CT10 MP3 player works much better as the MP3 player puts out a stronger high res audio signal.
Once you have made the above connections, start the audio source music playing and tune the radio receiver to about 600 kHz. Slowly fine tune the receiver up and down until you can hear the audio signal. It should be heard somewhere near 600 kHz, either slightly above or below.
Once you find the signal, try tweaking it by adjusting R4 on the transmitter using either an RF tuning tool or a mini-screwdriver.
Experiment by moving the antenna wire back form the receiver and raising it and lowering it. How does position change the receiver’s ability to pick up the signal?
What are some other ways you can improve the transmitters performance?
I mentioned above that this is a dirty transmitter. This term means that the output signal is not well-filtered. Transmitted radio waves by nature produce harmonic signals on even multiples of their frequency. In fact, when you are listening to the radio output around 600 kHz, you are actually tuned to the first harmonic as the circuit’s output frequency is somewhere between 200 and 300 kHz (see oscilloscope photo above).
Try tuning the radio receiver slowly up the dial. You ought to be able to also hear the transmitted signal just below 900 kHz and again around 1200 kHz and perhaps just under 1500 kHz. These are all harmonic signals and this type of unfiltered signal would not be acceptable for any FCC licensed radio transmitting station – wheter commercial or amateur. Harmonics can be mitigated through the use of electronic filters.
It should also be noted that it is of course illegal for anyone not holding a valid FCC license to transmit radio signals. A commercial license is required to broadcast radio signals on the US AM band and it is also illegal for anyone to interfere with commercially licensed stations.
If you successfully build this circuit, you will see that it is not capable of transmitting a signal to receivers located more than a foot or two away at best. You should not modify the circuit presented here to further amplify the signal to gain further range.
If you would like to build this circuit, I have prepared a complete kit that includes a solderless breadboard, all of the necessary electronic components including the audio input jack, the battery snap, pre-cut jumper and antenna wires. I have also written highly detailed and illustrated step-by-step instructions that should guarantee a successful build every time.
The kit requires no soldering with a limited number of step-by-step instructions to make the project easy and fun withe guaranteed success.
For a limited time, the cost of the kit including postage-paid shipping via USPS to domestic addresses is currently $22.00. The complete kit will be shipped in a padded envelope and instructions and documentation will be sent in PDF format via email.
Solderless 555 AM Transmitter Kit
Domestic US Customers Only
Thanks for reading and please share your thought and experiences. You may drop me a line at firstname.lastname@example.org.
As I write this in May 2021 there is much excitement in the amateur radio community as Solar Cycle 25 has been confirmed to have finally begun.
Every 11 years or so, the Sun’s magnetic field completely flips. This means that the Sun’s north and south poles switch places. Then it takes about another 11 years for the Sun’s north and south poles to flip back again.
The solar cycle affects activity on the surface of the Sun, such as sunspots and solar flares which are caused by the Sun’s magnetic fields. As the magnetic fields change, so does the amount of solar activity on the Sun’s surface which produce large emissions of radiations from the surface of the sun into space.
For amateur radio operators high solar activity means more favorable conditions for operating DX, or making long distance contacts. Radio waves, which are electro-magnetic can be reflected off of highly ionized layers of the earth’s atmosphere. The more ionization in the atmosphere, the better the operating conditions. When solar flares release radiation into space, that radiation will increase the ionization of the atmospheric layers where radio waves are reflected.
Thus operation conditions and the opportunity for DX contacts on the HF bands is expected to continue to improve as we head towards the anticipated peak of Solar Cycle 25, which should occur in 2025. This is great news for holders of General and Amateur Extra Class licenses as they both have broad privileges to the HF bands that will benefit from the increased solar activity.
The majority of amateur radio operators holding the entry level Technician Class license typically enjoy their on air time, operating inexpensive handheld transceivers to make contacts via local FM and DMR repeaters. Many Techs may enjoy the thrill of making “DX” contacts working other hams around the world via VOIP platforms like IRLP and Echolink which are accessible with their VHF/UHF privileges, but few take advantage of the opportunity to work “real RF DX” on the 10 meter band where they have limited HF phone privileges from 28.3 – 28.5 Mhz.
This is understandable, assembling an HF amateur radio station can be a daunting undertaking, and expensive. A new entry level multi-band transceivers such as the Icom IC-718 costs $600, and you can spent thousands more for more feature packed rigs.
Then there is the matter of choosing and raising an antenna for HF. This can be daunting as there are many varieties of antenna designs and there are many variables to consider.
Assembling a full featured HF station can be costly, complicated, and given that Technicians can only operate on the 10 meter band, doing so is a bit of overkill, at least until they upgrade.
This article provides information for the Technician licensee who would like to get on board to work DX on the 10 meter band as solar conditions improve. I will provide a technical primer on the 10 meter band and then thoughts, ideas and instructions on how to assemble a 10 meter only station, which not only easy and fun, it can be done for a fraction of the cost of building a multi-band HF station.
About the 10 Meter Band
The 10 Meter band is a low noise daytime band ranging from 28.000 – 29.700 MHz is at the very top of the HF frequency range. Here is the band plan for 10 meters:
If you would like to learn more about the 10-meter amateur radio band, may I recommend this excellent video by the Official SWL Channel on YouTube.
10 Meter Propagation
At peak times of the solar cycle, 10 meters will be alive with DX, refracting from the F2 layer in the ionosphere. The best propagation of 10-meter radio waves occurs during local daylight hours, but it is not unusual for the band to be open before sunrise and continue into the night when there are high sunspot activity.
The F2 layer forms during daytime hours between 200 km and 400 km above the earth. It is usually around all year around, and is at a higher altitude during summer months than in the winter. At night, the F2 layer will merge with the F1 layer to form a single F layer, which will be a bit lower in altitude than the F2 layer was during the day. Although the F2 layer exists all year long, it may sometimes disappear completely for days during a deep solar cycle minimum
In times of solar minimum, long distance contacts are still possible on 10 meters as Sporadic E propagation can bring in signals from a hundred to many thousands of miles away. Sporadic E is primarily seasonal with late spring and early summer being prime time for the mode.
Sporadic E arises when very intense clouds of ionization build in the lower reaches of the E region of the ionosphere. Sometimes these dense ionized clouds form suddenly and disappear just as suddenly minutes later. Sporadic E occurs most often in the months of June & July and December in evening, but it can happen at anytime. During a Sporadic E incident, ionization may be up to five times greater than those normally achieved at the peak of the sunspot cycle.
The 10 meter band is the only HF band that is affected by Sporadic E propagation, is typically benefits the VHF range including 6 and 2 meters, but typically won’t affect frequencies below 28 MHz.
Assembling your fixed 10-meter station – Choosing a transceiver
The most essential piece of an amateur radio station is of course, the transceiver. Even with the mythological perfect antenna, you need a receiver to hear other stations and a transmitter to put your signal out.
Most commercial amateur radio transceivers today are multi-band, that is, they can operate on most or all of the MF and HF ham bands, and several will also have functionality for all mode VHF and UHF operations. You can spend anywhere from about $500 to several thousands of dollars for a state of the art HF transceiver, and this may make the prospect of setting up a station to work 10 M phone only a non-starter for the Technician.
Fortunately, there are more reasonably priced alternatives available in terms of new and used 10 meter only radios. A careful shopper can expect to pay anywhere from under $150 to $500 for a used or new radio.
My recommendations – used 10 Meter Rigs from the 1990s
I recommend the Technician looking to get on 10 meters first consider purchasing a used 10-meter only radio that is in good operating condition. In the 1980s through the early 2000s, Radio Shack, President and Ranger marketed 10 meter radios that have SSB phone functionality. If not abused and relatively well cared for, these radios will be an excellent choice for the 10 meter Technician.
Among these radios, I recommend the Realistic HTX-100, also marketed as the President HR2510, from 1988 into the 90s. The radio was manufactured by Uniden and featured 25 watts PEP output on CW and SSB. This radio lacks FM functionality, so you could not use it for 10 meter repeater operations. Today they can be found in working condition in the $100 – $200 range at hamfests, on QRZ.com and on eBay.
When shopping for an HTX-100 or HR2510, do be careful. Carefully examine the radio or seller photos and inquire not only whether the radio is fully functional, but find out if the radio had been modified. These radios were popular for mods, particularly for out-of-band transmitting. Ideally you want to find one that hasn’t been modified.
Watch for obvious signs of modifications, damage or abuse/neglect. Several of these radios today suffer from black marks on the LCD screen. As long as the frequency and other information on the display aren’t obscured by the black marks, the problem is only cosmetic and won’t affect the radio’s useability. Do watch for units that have no display functionality at all.
Another problem with these used radios is sometimes the frequency can’t be changed via the rotary encoder tuning knob. Radios in this condition can usually still be tuned via the up-down frequency buttons. If you decide on a radio with this malfunction, make sure the price you pay reflects this.
The President HR2600 was a follow up more upscale revision of the HR2510, also made by Uniden, but this time not available from Radio Shack as a Realistic variant. In addition to SSB and CW, the HR2600 was capable of AM and FM operation, and even included a CTCSS tone board for repeater operations.
Like the HR2510, the HR2600 had a power output of 25 watts PEP for CW and SSB, and could put out 10 watts on AM or FM. The same caveats as listed above for the HR2510 apply for shoppers looking for the HR2600. This radio can also be found in the $100 – $200 price range used today.
In the late 90s and early 2000s, Radio Shack marketed another 10 meter only mobile rig, the HTX-10. The HTX-10 was manufactured by Maycom. The chassis of the HTX-10 was considerably smaller than the HTX-100, more in line with mobile 2 meter FM or CB transceivers of this era. The HTX-10 did not have CW functionality, but did have AM, FM and SSB phone modes. The transmitter put out 7 watts PEP on AM, and 25 watts on SSB.
The HTX10 can be found on eBay and QRZ to this day and you can expect to pay anywhere from $100 – $150 for a unit in good operating condition.
Modern Options, aka “Export Radios”
Today most of the new radios sold as “10 Meter” radios are in fact not so much as intended for amateur radio operators, but for people to modify and operate illegal power in the CB band, or 11 Meter Range.
By law, CB radio operators are limited to 4 watts PEP in AM mode and 7 watts PEP when operating SSB. In 1982, President Regan signed into law a bill that allowed the FCC to stop issuing individual CB licenses and to scale back enforcement of operating rules on the citizen’s band.
Although the law eliminated the need for individual licenses, the FCC never changed the rules or regulations for use of CB radio. To this day it remains illegal to operate a CB radio with more than 4 watts PEP on AM or 7 watts on SSB.
Despite this, many folks today run illegal power in the 11 meter band and do so outside the pre-defined channel frequencies. They do this by either adding an amplifier to an existing CB radio, modifying a pure CB radio to put out more power, or converting a 10 meter amateur radio transceiver for use on the 11 meter band.
Several manufacturers today sell what are known as “export radios” – these are CB radios that can not be legally sold in most countries. Either the power output is too high, the frequency range is too wide, or some modes aren’t allowed. Some manufacturers use is to initially limit the frequency range to 28.000 – 29.700 MHz and advertise these radios as ham radio transceivers making them legal to sell to the amateur community. The majority of customers who purchase these radios are not amateur operators but radio scofflaws who will modify them into an (illegal) CB radio.
The catch for you, however is that these are actually what they claim – 10 meter amateur transceivers and they can be used to operate on 10 meters. Several are inexpensive and some are lacking in quality. Here are a few worth considering.
Ranger Communications is a CB and amateur radio manufacturer based in Taiwan with a USA division. Their radios have been manufactured overseas in plants in Vietnam, Malacca, Malaysia, Shanghai and Taiwan.
For years Ranger has sold a series of 10 and 12 meter radios for several years all featuring a similar form factor. This line of radios includes the RCI-2950 and RCI-2970 radios and in addition to being available used, new radios are still being produced with various features and identified by the model number suffix.
The Ranger RCI- 2950CD is a 10/12 meter transceiver that puts out 25 watts PEP on SSB and 8 watts on FM/AM and CW. The radio has a current MSRP of $290 new.
The Ranger RCI-2970N2 DX is a 10/12 meter transceiver that is capable of putting out a whopping 200 watts PEP on SSB and 100 watts on FM/AM and CW. It has an MSRP of $450 new.
In Feburay 1992 QST published a side-by-side comparison of the Ranger vs. the HTX100. In conclusion, the HTX came out ahead overall, and the ARRL was “generally disappointed with the RCI-2950. If you have any doubt who the Ranger line are marketed for, consider the fact that these radios have CB features such as the “roger beep” and PA, and adding ‘talk-back’ is a very popular mod.
Anytone, known today primarily for their DMR handheld and mobile radios, also offers a pair of 10 meter mobile radios. The current iteration is the AT-6666 and can be had from Amazon.com for $266 at the time of this writing. It puts out a hefty 60 watts PEP on AM and SSB, and 50 watts on FM.
The previous version, still available new is the AT-5555N. It puts out 30 watts PEP on SSB and FM, 12 watts on AM. Currently it can be found on Amazon for $230. I have not read or seen any reviews of these radios, but if you have used either, please feel free to drop me an email at email@example.com.
Of course you will need a resonant antenna in order to put your signal out on 10 meters, and the easiest and most inexpensive way to do this is to construct a classic half wave wire dipole antenna. Building your own 10 meter dipole is simple, easy, affordable and fun.
The dipole is a straight electrical conductor consisting of two equal lengths of #12 or #14 stranded wire with a combined length measuring 1/2 wavelength from end to end. It is supported with rope or nylon cored from the center and each end and connected at the center to a radio-frequency (RF) feed line that is then connected to your transceiver.
A half wave dipole cut and tuned for the center frequency of 28.400mhz should cover all of the Technician 200khz spread with low SWR and will allow you to work the entire sub-band without the need of a tuner.
Here is a list of all materials you will need for your dipole:
20’ of 12- or 14-gauge copper stranded wire
Coaxial feedline – RG8X is sufficient and light
Connectors and insulators
1:1 Balun (RF Choke), optional
The insulators can be homebrewed from any non-conductive material (glass, plexiglass, PVC, wood, commercial made insulators, etc. The center insulator actually can be used both for support at the center and to prevent the two outer radiators from touching and needs to be able to handle the weight of the entire antenna, coax and support ropes. if you incorporate the RF choke, that will do double duty as your center insulator.
A brief aside… Balun or no Balun?
Many recommend incorporating an RF choke or a 1:1 current ‘balun’ at the point of where the feedline meets the antenna elements. The word balun is an amalgamation of the words balanced and unbalanced and it provides common-mode isolation between the antenna and feedline. In our model, we only need it as an RF choke and serves the purpose preventing stray RF from coming back down the shield of the coax and into the shack.
My recommendation is that you may wish to initially construct your antenna system without the choke, and later modify the antenna if you experience a problem with stray RF. You will know you have a problem with stray RF if you experience RF burns, or you note RF interference with other electronic devices such as PCs, televisions, digital clocks while transmitting.
There are many 1:1 baluns available commercially from reputable manufacturers and retailers such as DX Engineering, Jetstream, MFJ, Quicksilver Radio and Radiowavz. A good rule of thumb in buying a balun is you can expect to get what you pay for – expect to pay $30 – $100 for a good balun and maybe avoid AliExpress, BangGood, and eBay. Expect to pay $30-$100 for a quality commercial current balun
You may also wish to construct what is known as an ‘ugly balun’ – which is easily constructed with a 25 feet of spare coaxial cable and should be effective eliminating stray RF issues. There are numerous resources for this on the web if you’re interested. Start with this HamUniverse article and/or watch Jim Haslett’s “How To” video here.
Choosing your feedline
Just as you need to make compromises when choosing an antenna, design, you need to select the best balance of different factors for your installation when choosing a coaxial feedline. These include:
For the 10 meter dipole, weight is your primary concern, followed by line loss and cost. Heavier feedlines add more strain to the antenna connections and support rope so a lightweight feedline is preferred. Regarding line loss, while higher frequencies mean higher line loss, at 28.3 – 28.5 MHz, still in the HF range, loss won’t be as significant of a factor as when feeding a VHF, UHF or higher band antenna.
RG8X provides a nice compromise of weight, loss and is particularly inexpensive. Calculated loss for a 50′ run of RG8X at 28.4 MHz with a load SWR of 1.5, is 17.84%. If you’re putting in 25 watts PEP under these circumstances, calculated power out is 21.89 watts; not bad at all. At the time of this writing, a 50′ run with SO239 connectors retails for less than $40 at QuickSilver Radio.
The last thing you will need to do before going on the air is to tune your half wave dipole antenna. The process is simple and straight forward.
The dipole antenna is to be tuned for the lowest SWR across the portion of the band you will be using it for. For our purposes, we want the lowest SWR for the Technician phone portion of the 10 meter band, which is 28.300 – 28.500 MHz. Tuning for lowest SWR at 28.400, the mid point of the Technician phone sub-band will allow the antenna to perform well across the entire Technician sub-band.
The tools needed to tune the dipole are a pair of wire snips, a ruler, and either an HF antenna analyzer, the SWR meter built into your transmitter, or a stand alone SWR meter.
An antenna analyzer such as those by RigExpert or MFJ Enterprises is a handy tool for the radio amateur. These devices transmit low power RF to the antenna and provide a reading of SWR across a selected range of frequencies. However, new these meters cost $300 and up. Your elmer or local club may be able to loan you an antenna analyzer and even help you use it.
If your transceiver has a built in SWR meter, that can be used to tune the antenna. Stand alone SWR meters are relatively inexpensive and may also be used and placed between the antenna out PL259 on the rig and the coax feedline. If you are using your rig and an SWR meter to tune, you will need to set the radio for CW or FM as you need to transmit a carrier wave to get an accurate SWR reading.
Raise the antenna into the air from the center insulator or balun and each of the ends. You may configure the antenna in an “Inverted V” position where each of the elements slope down at an angle of 45 degrees from the center insulator.
Take an SWR reading at 28.3 and 28.5 MHz.
Average the two readings. Ideally you are looking for an average SWR of 1.0 to 1.5.
As long as the reading at 28.3 MHz is less than the reading at 28.5 MHz, the antenna is too long. Lower the antenna and snip off 2 inches from each end of the antenna. Make sure that the two elements remain the same length.
Raise the antenna again, return to step 2 and repeat the process. Continue until the SWR falls into the desired range.
Once your dipole is in tune, you won’t have to fuss with it nor will you need to worry about using an antenna tuner. A properly tuned 10 meter dipole will be sufficiently resonant across the 0.2 MHz width of the Technician sub-band.
You’re on the air – congrats! Now what?
Now that you’ve assembled your 10 Meter station, it’s time to get on the air! But what can you do?
To help determine whether the band is ‘open’ or not, you can listen for beacons. Becaons are weak signal stations (less than 20 W, more commonly 1-3 watts) transmitting from various locations around the world – if you can hear the beacon, the band is open between you and the QTH of the beacon station. You can find a list of 10 Meter beacons here. Check out the Official SWL Channel video “What are 10 meter beacons?” to learn more.
On the air, you will find much to do on 10 meters. Beyond the anticipated DX openings due to Sporadic E and the increased solar activity from Solar Cycle 25, you will find special event stations and contests on the 10 meter band. Many of these events are produced and promoted by Ten-Ten International, a global organization first founded in 1962 in California, that promotes 10 meter activity and good operating procedures.
Membership in 10-10 is easy to achieve – all it takes is working and collecting the 10-10 number of ten members, plus $15 annual dues. In addition to programming on air events, 10-10 also publishes a quality quarterly, 10-10 International News.
The MARC/Castle Craig 10-10 Chapter holds a weekly net every Tuesday night at 8:00 pm local Eastern time at 28.375 MHz. Everyone is welcome to check in! If you’re not in the New Haven locale, look for 10 meter nets in your area. There are many out there, you may be surprised to find an active group near you.
I hope you found this article informative and useful. I hope it may have inspired you, whether you are a Technician or hold a higher level license, to get on 10 meters and enjoy the anticipated DX in the next few years. Spread the word – 10 meters is coming back!
Feel free to drop me at firstname.lastname@example.org if you have questions or wish to provide feedback.
It had become a long running joke with my wife Ellen, and her best friend Naomi, who has been coming over for socially distant weekend visits ever since lockdown began in March. When Nay would arrive most Saturdays around noontime, she’d find me outside with my head stuck under the dashboard of my 2012 R56 MINI Cooper and she’d ask Ellen if I was ever going to finish my car project. Truth be told, it really wasn’t ‘one’ car project that I undertook during my summer of Covid, but several automotive upgrades. The focus of this post however, is the installation of two transceivers to create my new mobile “ham shack.”
A SIMPLE PROJECT EVOLVES
It all started when I decided to replace a blown factory speaker. Well, speakers are sold in pairs and why upgrade the front speakers only? Soon a package arrived from Crutchfield with a complete set of premium aftermarket speakers.
Replacing the speakers took me back to my teen years when I installed that Kraco Dashmsater AM/FM/MPX stereo that I bought at K-Mart for $30 in my Ford Pinto along with matching 5″ Kraco slimline speakers mounted in the cardboard rear deck. That Christmas mom & dad made my holiday by getting me the Realistic 40-watt amplifier and graphic equalizer complete with 7 sliders and flashing LEDs that I ‘needed’ to complete my ride! (You can bet your figgy pudding that I was outside right after Christmas dinner in the subfreezing weather with my wire cutters and electrical tape racing to complete my hi-fi upgrade before sundown!)
So feeling nostalgic, I didn’t stop at the speakers and soon a reasonably priced Kenwood eXcelon DPX594BT double-DIN stereo had also arrived from Crutchfield with bells & whistles that I couldn’t have imagined in my Kraco Krankin’ days – SiriusXM, Pandora, Spotify, Alexa, Bluetooth, USB, a CD player and of course good ole AM/FM.
The second-generation MINI Cooper features a big ole Speedometer in the middle of the dashboard and the bottom half of that speedometer is where MINI incorporated the factory radio display and memory buttons. The aftermarket stereo dash kit came with a blank out panel for the factory display and buttons, but this left sort of an unfinished empty look right in the middle of the dash.
And this my friends, is where the inspiration came in. That big empty space looked like prime territory for a transceiver faceplate. A couple of years ago I purchased a Yaesu FT-891 with the intention of building a Go-Box that I hadn’t done anything with. I saw that the Yaesu remote head and mounting bracket could neatly be attached to the speedometer blank out plate and this would be an excellent use for the space. The ‘bug’ bit hard and before you knew it, I was all in on making this happen.
HOW IT ALL CAME TOGETHER
I decided to install not only the HF rig, but also my Alinco dual band UHF/VHF DR735 and I began the project by bolting both radios to the back of the rear passenger seat, with plenty of slack cable so the rear seat could be folded down. I routed the control head cables under the door sills under the edge of the carpeting and on up to the dashboard. So far, so good.
To power the radios, I ran a 10 AWGdirect line from the battery, through the firewall and under the center console back to the trunk area. The MINI has a nifty little carpeted access panel for access to the taillights so I used that space to mount a PowerPole distribution block at the back of the car to not only power the two rigs, but to provide a convenient place to plug in any other 12VDC gear I might want for a future outdoor radio event, say Field Day.
One concern that arose was that both radios had speakers built into the radio bodies, which were now in the trunk. Not so good for this old fart with failing hearing. I thought about adding an accessory speaker on the dashboard, but in such a small car, space comes at a premium and I’ve already cluttered things up with two new remote heads and microphones.
I decided to try a creative solution and bought one of those cheap-O FM modulators that let you transmit audio from your MP3 or CD player to your car stereo. I mounted the tiny modulator above the PowerPole block, connected it to the radio audio output jacks, and tuned it to 89.3 MHz, an unused frequency in my area. I programmed one of the FM memory buttons on the new Kenwood stereo to that same frequency, and now I get my ham radio audio through the stereo speakers.
For antennas, I went with the Yaesu ATAS-120 screwdriver antenna for HF and installed a lip mount on the rear tailgate. I was fully prepared to drill through the roof for a better mounting position with a much better ground plane, but my car has dual sunroofs – so that wasn’t a very viable option. On the other side of the tailgate you will find the 2M/70cm dual band antenna attached by another lip mount.
The last time I had a mobile installation was about a dozen plus years ago when I installed a Yaesu FT-857D in my 2002 Ford Focus sedan and used a four-magnet trunk lid mount with interchangeable mono band ham-sticks. I did have a lot of fun in those days working into Europe on 20 and 40 M after work while stuck in the parking lot that is rush hour on Route 128 outside of Boston.
When I did the Focus install, I took the matter of bonding seriously and used copper braid to bond the doors, hood, hood, and rear hatch to the main body. However, realizing that all of the doors should have a good ground by means of being bolted to the body, I haven’t yet bonded the doors on the MINI This SEEMS logical, but I don’t know – I welcome your insight and feedback here. I did add a beefy ground cable from the antenna mount to the rear hatch sheet metal for a better ground.
HOW DOES IT WORK YOU ASK?
So far, so good – I have made some initial HF contacts on 40M along the east coast and into Nova Scotia, have checked into ECARS on my morning errands, and I have also participated in the local Meriden Amateur Radio Club Tuesday Night 10M net.
I’m pleased so far with the performance, but I have discovered that the ATAS antenna tunes slowly – I may need to beef up the ground connection on the lip mount – and of course it’s placement is far from optimal. I may try some of my ham sticks left over from my first mobile installation with a mag mount on the roof to see how it compares. So far I’ve not noticed significant alternator/engine noise on receive, nor have I received any audio reports indicating whine on my signal. I did notice, however while transmitting on 10M, it causes the LCD screen built into my rearview mirror to flutter.
The bottom line is I’m quite pleased so far and look forward to making any necessary tweaks going forward as I make more contacts with my motorized MINI go-kit!
EPILOGUE… WHAT ELSE DID I DO TO MY MINI?
I mentioned that I did several upgrades/mods to my MINI Cooper this summer, besides the radio mods detailed above. In addition to the radio projects outlined above, here’s a list of the additional things I did to “Hubert,” my 2012 R56 MINI Cooper this summer…
I installed a Rockville RW10CA 10″ 800 Watt Slim Low Profile subwoofer in the trunk. I had underestimated the size of the subwoofer. Despite the words “slim” and “low profile” in the product description, I discovered it did not fit under the front seats, as originally planned and it occupied a lot of the limited available trunk space. My solution was to make it easily detachable and removable using PowerPole, RCA and RJ11 connectors.
I installed a pair of Wipac 5 1/2″ driving lamps. I always liked the way auxiliary driving lamps looked on both the classic and new MINI. I saved a significant portion of the cost by choosing Wipac over MINI lamps. The MINI lamps are expensive and make use of a proprietary mounting bracket that will not accept other manufacturer lamps.
I also attempted to upgrade the headlights. Like many MINI R56 owners, I felt the OEM halogen lamps were too weak. I purchased a set of aftermarket extra-bright LED low/high beam bulbs. The bulbs were simple to install, however the new LED headlights flickered incessantly. Apparently this is a fairly common occurrence that can be resolved by adding a resistive ballast to the circuit. I purchased a plug and play ballast set but was saddened that it did not completely resolve the flicker issue. So I’m back to the OEM headlights for the time being.
Twenty years ago this August, I played a small part in starting an Internet photography thing, that frankly I’m surprised has lasted so long.
Along with a few internet friends in an online camera group, the Argus Collectors Group, we sought to start an annual “Argus Day” to celebrate and promote this beloved brand. Participants in Argus Day would be encouraged to take their favorite Argus camera with them wherever they went that day to take photographs and to spread Argus awareness. The ACG would publish submitted photographs taken on Argus Day in an online gallery.
With an eye to making Argus Day a little more distinctive and just a bit quirky among the various film camera days, it was decided that instead of occurring on the same day each year, each subsequent Argus day would occur one year + one day from the previous year’s observance.
The first Argus Day was held on Argust (August – ha!) 1st, 2001. The second was on Argust 2, 2002, the third on Argust 3rd, 2003, and so on. As I mentioned, this year marked the 20th edition of Argus Day, and accordingly, it rightly fell on Thursday, Argust 20, 2020.
My love of Argus cameras began when I was 12 or 13 years old when dear old dad, handed down his old Argus C3 Standard rangefinder camera to me. Dad loved photography and shot some amazing Kodachromes during his two hitches in the US Army while stationed in Greenland and then in Germany. Dad only shot slide film and the sensory experiences of those special nights when he’d come home from work with a new set of slides from his most recent completed roll of film remain etched in my memory to this day – the bright yellow Kodak box of slides, the dusty smell of the portable projection screen, the ker-chunk of the carousel projector.
Dad, a frugal man, never sent a roll for processing before it was completely exposed so some times we were viewing Easter slides, while seeing the prior year’s Christmas shots at the same time. The best slide shows were the nights when dad would honor our request and show slides from his Army days, or when he was sparkin’ mom. The images were color saturated and beautiful and it was fun listening to dad and mom recount those earlier days.
Prior to receiving my C3 from dad, I had cut my teeth (photographically speaking) first with mom’s old Kodak Brownie Hawkeye box camera when I was nine or ten. From there I moved on to using a Kodak Pocket Instamatic in junior high school. The Kodak took photos on the then ubiquitous and pretty inferior 110 film cartridge. I remember taking that camera on my 8th grade field trip to Washington DC. Pretty much all of my classmates were carrying similar low-end110 cameras from a variety of manufactures.
Dad was pleased with my composition of those DC snapshots and told me that my good work merited his old Argus. Wow! I was thrilled…. finally a “real” camera – with all the proper adjustable settings – aperture, shutter speed, and focus!
Of course, the Argus was more than a little outdated by the late 1970s when I received it. By that time there was a growing variety of high quality consumer single-lens reflex cameras available with superior optics and advanced electronics including the Canon AE-1, the Nikon FM, the Olympus OM-1.
By 1978, the time of the rangefinder camera had already come and gone, and in fact, at the time when my humble Argus “brick” was new in the mid-1960s, Japanese manufacturers had already redefined what a 35mm rangefinder camera was, offering a plethora of more feature packed compact rangefinders in smaller and more ergonomic bodies.
Compare the mid-60s Argus C3 Standard alongside the Canonet QL19.
Yes, I would have loved a Canonet or Yashica Electro, but I was only 12 years old and my only disposable income came from my weekly allowance. I truly loved my Argus and I took it everywhere with me for the next several months until the flash sync started malfunctioning. Then, once again, dad came to the rescue as I started high school – handing down an even cooler vintage camera – his old East German manufactured Ihagee Exa SLR. Perhaps that will be subject of a future blog post. But for now, back to Argus…
What’s an Argus?
Given the important role that the Argus camera played in making 35mm the popular film format it because, it’s somewhat sad that more Americans don’t know much about Argus.
The Argus camera came into being in the mid 1930s, when Charles Verschoor, the president of IRC, the International Radio Company in Ann Arbor Michigan saw the compact Leica 35mm candid camera while in Europe. Before the advent of the 35mm film cassette, the camera the typical household was most likely to own was a either a simple medium format box camera like the Kodak Brownie, or perhaps a simple folding camera like the Ansco Readyset. They were not compact, they were not particularly easy to use, and they typically didn’t produce high quality images.
IRC was a manufacturer radio receivers and had established a sweet niche in that market producing ‘compact’ Kadette radio sets many of which were housed in cabinets made of primitive plastics, such as Bakelite. But radio sales were highly seasonable – up in the winter months when families stayed indoors and radio propagation conditions were better, and down in the summer months when more folks were out of doors and radio reception was poor.
Verschoor was looking for a second product line to help level out the annual revenue stream for IRC and the new 35mm camera seemed to fit the bill. IRC’s collaboration with existing plastic firms would be beneficial providing a source of inexpensive sturdy and lightweight bodies for their cameras.
In 1936, IRC introduced the Argus Model A, and the rest, as they say, is history. It was an instant success, selling 30,000 units in its first week. Argus quickly introduced a variety of other models with more features, including the Argus C line of rangefinder cameras, first introduced in 1939, which featured a built in rangefinder to set the focus.
It’s almost impossible to overstate how responsible the Argus camera was for making 35mm photography as popular as it became. If you wish to learn more about the Argus A and how it changed photography for the every man, I highly recommend Hrad Kuzyk’s free book, 35mm for the Proletariat. For a deeper dive into the company and it’s photographic products, get a copy of Henry Gambino’s 2005 book, Argomania: A Look at Argus Cameras and the Company That Made Them.
But what is the Argus Collectors Group?
At the dawn of the interwebs in the mid-90s, I discovered out this new thing called eBay where you could bid on and buy all sorts of nostalgic treasures from your past – things you had long since discarded as ‘junque.’
It didn’t take long for me to acquire a new used vintage Argus C3 camera and I was magically transported back to my childhood. I started taking my new brick with me everywhere, and found it was quite the conversation starter. I remember showing it to my dad on one of my visits home, and he just smiled and laughed when he saw it – it brought back fond memories for him too.
At the same time, I came across an internet SIG called the Argus Collectors Group, a global virtual community of similar Argophiles who were obsessed with their Argus cameras.
What a group! I learned much about Argus history from that dynamic community while making many good friends. The group was created as an offshoot of the IDCC, the International Directory of Camera Collectors. Noted Seattle camera collector and historian, Bob Kelly, was our group’s moderator at the time I joined. When he retired from the task, I took over the role for a couple of years before passing the mantle on to Wesley Furr, who has provided steady leadership ever since.
The ACG remains a very active and dynamic group and continues to grow to this day. Over the years, this close-knit group has undertaken a number of projects and programs, including an annual Holiday Lights photography contest, and the Argus Argosy, where members passed a single Argus camera from photographer to photographer from around the world to make a global online gallery.
The ACG’s premiere annual event is the ACG Gathering, organized by Ron Norwood and our late and sadly missed friend Doug Wilcox. The Gathering was first held in Martinsville, VA in 2001 before taking up residence ever since in Eden, NC. Today the ACG is closely affiliated with the Argus Museum in Ann Arbor, which also hosts an annual Argus Conference each October.
Argust 20, 2020
I end this post sharing some of the photographs I made this year on Argus Day. You will be able to see my two submissions, along with my wife’s and many other photographs from the many talented ACG members online here going all the way back to the second Argus Day (sadly, the first Argus Day gallery was lost when we changed host servers.)
Ellen and I have been fortunate enough to be able to continue to work from home during the Covid 19 pandemic, so this year we both participated from home. She photographed our gardens with an Argus 75 box camera while I took a lunch time walk around our hometown of Cheshire, CT with my favorite C3, a 1948 seven speed variant, serial number 233428 loaded with Ilford Pan F+ 50. I developed our film with Rodinol, scanned the negatives and then tinted them in Photoshop.
I welcome your comments and feel free to drop me a line at email@example.com. Thanks for looking!
Material for this blog post was originally presented on the Meriden Amateur Radio Club Tech Net, on August 20, 2020, a 2 meter net held on the first & third Thursdays of the month on the W1KKF, 147.360+ MHz repeater in Wallingford, CT, and simulcast on Zoom.
My love of amateur radio goes all the way back to childhood when I would waste hours in my grandfather’s workshop in our basement building Radio Shack Science Fair kits and mucking around with all the dead radio and TV carcasses he accumulated. I have been melting solder for the better part of my life and to this day still love building kits and recapping, repairing and realigning vintage radios.
However, my skills have never been great… I lack what many employers have rudely called an “attention to detail.” All these years later, I’m sorry to say that still the majority of things I put together don’t initially work as they should.
I used to get discouraged but then realized this was actually a gift – – – instead of abandoning a non-functional project, which would make it a waste of my time and money, I have discovered the process of troubleshooting actually gives me more bang for the buck.
Troubleshooting requires a deeper dive in order to learn and understand how the circuit works which reinforces my electronics knowledge. Finding and fixing a malfunctioning piece of equipment is also very satisfying and rewarding – it’s like solving a puzzle, but in the end you get something you can actually use.
In this blog post, I’m going to cover some of the basics – including essential tools I use and the steps I take when tackling a new troubleshooting project.
Disclaimer – I am by no means an expert, I believe I’ve made that clear. What follows is intended to be foundational and inspirational to others who have been frustrated when troubleshooting electronic appliances. More advanced techniques dealing with specific circuits is beyond the scope of this post. Look for future posts dealing with more advance RF troubleshooting topics.
THE ESSENTIAL BENCH TOOLS
The most basic tools you will need for troubleshooting include:
A good stable bench power supply You might be surprised the number of electronic problems are due to no or insufficient juice, reversed polarity and blown fuses.
A quality Volt-Ohm-Meter (multimeter) is essential for measuring voltages, current and resistance values. Today the majority of meters are digital and there are many serviceable units to be had for an inexpensive price. A good workbench should have both digital and analog meters. Analog meters still have an edge over a digital meter in certain circumstances such as when reading fluctuating signals (current), as digital meters typically give you an average reading. This is an advantage when trying to peak a tunable circuit.
Good magnification is essential for troubleshooting, especially when working with today’s miniscule parts and circuit boards with surface mount components. Either a good magnifying desk lamp, or a plug-and-play USB Microscope that plugs into your computer is going to be invaluable. Like very one else who has made it to middle age, I have experienced waning vision (which pretty much sucked since ever since I started wearing glasses at age 2), and dexterity. I got my magnifying desk lamp on Amazon and my USB microscope from QuickSilver Radio, a favorite source for ham radio cables, small parts and tools. TECH TIP:In a pinch, your cell phone can be used to provide quick and dirty magnification. Simply use the camera to photograph the part you need to magnify then open the photo and zoom in – we are living in a Golden Age, my friends!
Temperature controlled soldering iron and tools. This is not an area to cut costs. Growing up I soldered with inexpensive solder irons from Radio Shack, seldom concerned with what their wattage ratings were – 15? 30? 45 watt? – Whatever it takes. I have learned in recent years the importance of a good temperature controlled solder station as well as the importance of using the correct iron tip for the application. This upgrade has been a game changer improving the quality of my solder work, while reducing my stress and frustration. It’s important to not use too much heat when working with delicate components and circuit boards, and it’s equally important to use too little heat when soldering joints.
TROUBLESHOOTING TIPS & TRICKS…. FIRST THINGS FIRST
The very first step in attempting to diagnose electronic equipment failure is to clearly define the problem., that is, what specifically is not working and also importantly, what else isn’t working?
Create a list of all symptoms and indicate whether the symptoms are intermittent. If intermittent, does the symptom occur when a specific control is activated? Does the problem stop if the appliance is moved or re-positioned? Once you have a list of symptoms and circumstances, evaluate the list – which symptoms might be linked? Where is there commonality to what is failing? Documenting and understanding all the symptoms can be useful.
The second thing to evaluate is the power situation. Technicians who do a lot of troubleshooting identify lack of power as the number one reason why a piece of equipment isn’t working. Sounds simple, but the question “Is the unit plugged in?” is foundational.
Make sure there is a fuse in the fuse holder, and that it isn’t blown. If it is blown, it will take more than just replacing the fuse, but you will know that something is awry with the power circuits – either a short or a failed component creating an overdraw of current.
Make sure that DC polarity is correct, and make sure there aren’t any broken power leads, disconnected power connectors, or cracks in the circuit board or broken traces around the power supply circuit.
After assessing the power supply, next up is an in depth visual inspection – this is where the magnifying tools come in handy. Carefully inspect both sides of the circuit board looking for obvious issues such as:
Damaged/burnt out components
Signs of previous ‘work’
Obvious mods, parts replacements
Excess flux, solder blobs and cold joints
TIME FOR THE DEEPER DIVE
If your circuit is getting proper power and you didn’t find any obvious problems after a thorough visual inspection, it’s time for the deeper dive. This will involve gathering, reading and understanding all the circuit documentation you can get a hold of. This documentation includes:
Chassis and Parts Layout
Manufacturer Manuals and Supplements
Third Party Manuals ( e.g. Riders, SAMS PhotoFact)
Don’t forget about local resources, namely your local amateur radio club where you will find numerous older and wizened “Elmers” who are generally happy to pass on their expertise.
My local amateur radio club, The Meriden Amateur Radio Club here in Connecticut runs an open house every Saturday morning at the Wallingford EOC where we are headquartered. The open house features a repair bench staffed by the likes of NZ1J, Dave, KE1AU, Bob, and WB1GYZ, also Bob, who are always up for a new challenge.
WHAT’S CURRENTLY ON THE AB1DQ WORKBENCH? (a troubleshooting case study currently in progress!)
Earlier this summer I constructed the MFJ 9340 40 meter QRP Cub Transceiver kit. This kit was not unlike many others I have built in the past including the WA3RNX 40 meter transceiver, and the Wilderness Radio SST 20 meter transceiver kit. The MFJ kit came with a circuit board pre-populated with all of the SMD components and required the builder to install the traditional through the hole parts.
Construction went smoothly over two or three evenings and I was happy to find that I had no ‘spare parts.’ (A good sign.) I was able to align the receiver easily per the directions in the construction manual, however when I attempted the transmitter alignment, I ran into trouble. What happened?
I started troubleshooting with a good visual inspection focusing particularly on the solder side of the board looking for bridged solder joints. Nothing looked suspect.
Because this was a kit radio, I had just about all the documentation I needed in the manual to start trouble shooting including the Block and Schematic Diagram, a diagram of component lay out, and a page of Troubleshooting Tips too.
I started with these diagrams and breaking the radio down into separate functions and began color-coding the schematic, block diagram and parts layout. This took a bit of time, and you could argue it wouldn’t be necessary for a simple transceiver, but doing so did provide me with a solid understanding of how the radio was designed and where I can set my focus for finding trouble….
So now I know where the sub-assemblies and their parts are located on the circuit board, and I can trace the stages of the circuitry on the schematic, great! Now I need to go even deeper to see if I can find where the problem is originating.
The MFJ documentation had a table of voltages for each of the transistors and ICs. I am always thrilled when I can find a voltage table like this or see that proper voltages are indicated on a schematic.
I created a simple Excel spreadsheet with the MFJ data and carefully measuring the test points on my radio, I was able to calculate unit and percentage variances which allowed me to find trouble spots.
I quickly identified hat the biggest variances were found on Q6, the Transmitter Driver, U5 the Transmitter Oscillator chip and Q5 the Transmit buffer. None of that was a surprise since I knew my problem involved the TX function.
However, I also observed a sizable variance on the BFO buffer, Q4, which might be related…
[SLIDE 16] I marked the over/under voltage readings on my schematic and cross referenced the parts layout to determine where I needed to focus. These parts were pre-installed, so I worked backwards from each in the circuit to look closer for problems.
WHAT’S NEXT AND SOME KEY TAKEAWAYS
This may seem like a strange place to end a blog post, but as of the time this material was presented on the MARC Tech Net on August 20, 2020, I had not yet finished my troubleshooting work on the MFJ Cub.
Next steps on the project will be to trace back ‘upstream’ from the variances on the schematic and closely examine my work, verifying that I placed the proper components where they belonged, and that my solder joints are good – not cold, and not blobby and bridged. I also want to take a close look on the two torrid inductors in the TX filter, L10 and L11.
While I had hoped and planned to have completed my work on the Cub prior to the net, I was unable to, and that’s my final lesson for now.
When troubleshooting, don’t rush and don’t get aggravated. Take it slow, work methodically and logically. Never jump to conclusions at the first sign of something unusual too. Many times the problem isn’t obvious and many times too, it’s not complicated. Stick to it and in the end you will find yourself rewarded with a satisfied sense of accomplishment.
As for me, I will update my blog when I have discovered and resolved the problem with the MFJ 9340. Watch for that post, or feel free to shoot me an email if you have questions, suggestions or want to discuss further.
GENERAL TROUBLESHOOTING TIPS
I mentioned that this material was originally presented during a 2 meter net. I want to thank the following stations who checked into the net, and I will close with some bulleted advise, tips and tricks that were shared by the participants…
This past winter, my old high school buddy, who we shall call “Laurence” handed off to me his Zenith Model G724 radio, a nice 1950 Bakelite case table top AM/FM superhet. According to Larry, the radio played well but had a broken dial string.
Dial strings can easily be replaced using common twine, and while I had the radio apart, it made good sense to replace the old wax and electrolytic capacitors and to test the tubes – simple basic maintenance to keep this radio working.
This radio has a selenium rectifier to convert AC to DC [Figure F, below]. While I was aware that selenium rectifiers are prone to failure as they age, I have never experienced a failure – most of the radios I have serviced feature tube rectifiers.
Laurence had shared my Facebook post about the service I had done to his radio on a vintage radio forum where an astute member spotted the selenium rectifier and asked if I planned to swap it out for a diode.
I decided I needed to broaden my knowledge of selenium rectifiers and what happens when they do fail. I came across two useful YouTube videos from two content providers I already subscribed to – Shango066 and All American Five Radio – that helped me fill my knowledge gap.
What I learned from both videos was that selenium rectifiers put out reduced voltage as they age, not delivering enough B+ voltage for the tubes. I also learned that if the selenium rectifier shorted out and overheated it would smell pretty awful and could cause more damage to the radio.
A modern general purpose rectifier diode, the 1N4007 can be used as a direct replacement for the selenium rectifier, however the selenium rectifier has a higher internal resistance than the 1N4007 which means a dropping resistor needs to be added in series with the diode to prevent tube filaments from burning out due to too much voltage.
In order to determine the value of the dropping resistor, I consulted the Sam’s Photofact and studied the schematic and voltage notes to find a reference voltage. According to my documentation, the grid voltage on pin 5 should be 125 VDC+.
Using jumper cables I placed the 1N4007 in circuit with my Heathkit Resistance Subsitution Box in series and my Voltmeter connected to pin 5 of the 35B5.
With the resistance set to 33 ohms, the voltage on pin 5 was 124.9 volts. [Figure A., below]
Because the resistance substitution box was old, I wanted to check the resistance with my ohm meter – I discovered that the 33 ohm setting actually read at 39.1 ohms. [Figure B., below]
I chose a 36 ohm 1 watt resistor from my parts box for substitution and when I tested it with the ohm meter and it read 38.0 ohms. [Figure C., below]
I soldered the 36 ohm resistor in series with the 1N4007 diode and soldered it into circuit. [Figure D., above]
I then tested the voltage on pin 5 of 35B5 and found the substitution worked fine as the voltage reading was now 128.8 VDC+. [Figure E., above]
In the end, Laurence gets a tuned up Zenith and the next time I see him, I shall collect my friends and family fee – 2 snorts of Jack Daniels Whisky! 🙂
Please leave your comments on this site, or drop me a line at James@ab1dq.com!
I earned my first amateur radio license, the gateway Technician ticket, in March of 2002 at the age of 37. It had been a lifelong goal to become a ham radio operator every since the radio bug first bit back in the 1970s when I spent countless hours in my grandfather’s radio/TV workshop melting solder and into the early 1980s when C.B. radio was the craze and I first discovered the wonders of shortwave radio listening.
Had I pursued my dream in earnest back then, the entry level license I would have studied for would have been the Novice license, requiring me to pass both a written exam and a 5 word per minute Morse Code exam. However, that era ended in 2000 when the FCC stopped issuing the Novice license.
In 2002 when I was first licensed [as KB1IAR], although I did not need to pass a Morse code exam for the Technician license, I did need to pass the 5 WPM Morse code exam along with a written exam in order to upgrade to General class ticket which brought with it coveted HF privileges.
I passed the 5 WPM Element 1 Morse code exam along with my Element 3 written exam to upgrade to General a few months after earning my Tech, and a little over a year later I passed Element 4 to earn my Amateur Extra class license.
In earlier times, a ham radio operator needed to pass a challenging 20 WPM Morse code exam to upgrade to Extra class. Many older hams who worked so hard to clear this hurdle back in their day continue to sneer at us 21st century Extra class licensees, referring to us as “Extra Lites” while bitching and moaning about how licensing exams have been dumbed-down.
In 2003 the International Telecommunications Union ended the international Morse code requirement for an amateur operator to qualify for transmitting privileges on frequencies below 30 MHz and in December 2006, the FCC retired the Element 1 exam, eliminated all Morse code testing for US amateur radio licensees.
In the nearly 15 years since the Morse code exam has been gone, you might expect to find the CW bands dead, but I’m happy to report that Morse code remains a very popular operating mode today as amateurs like me are still drawn to and enjoy using Morse. It turns out that sending and copying code is a fun and worthwhile pursuit and ham radio operators are continuing to learn and use the code, not because they have to, but because they want to!
So given that there is a hunger for hams who have no code expertise to learn code, I hear the same question in a variety of amateur radio communities – either local clubs or online – “What is the best way to learn Morse code?”
When I was studying the code years ago for my General upgrade, I listening to Morse Code instruction lessons on cassette on my Walkman. The ARRL recorded code lessons, which are still available on CD, did an adequate job of teaching me to memorize the 26 letters, 10 digits, and various pro-signs at the dreadfully slow 5 WPM – sufficient enough for me to pass my Element 1 exam.
While it helped me earn my license upgrade, those recorded lessons did little to prepare me for operating CW on air. For the next several years I looked for other tools to improve my Morse skills and up my speed. These included online tools and smart phone apps.
Then I discovered CW Academy, a three tier interactive Morse code instructional class offered by the CWops organization. The classes are offered in 3 levels – Basic, Intermediate and Advanced and are held online via conferencing software such as Zoom. You meet twice a week with your adviser and several of your peers peers who are more or less at the same level of ability.
Classes typically meet online for an hour two times a week over an eight week semester. The course requires students to commit themselves to the program and there is nightly homework assigned so that you learn by immersing yourself into CW.
Several tools are used for homework assignments including MorseRunner and RuffzXP – two excellent interactive apps that simulate CW contesting. Nightly homework assignments also included listening to recorded sample QSOs and short stories intended to aid in developing good head copy skills.
Tonight I completed the CWAI (Intermediate) level course, and in all honesty, this is the second time I have taken the second level CW Academy course. I believe the key to becoming a good CW operator is to constantly use your skills – on air ideally, but by listening to code whenever you can. The Intermediate level course focuses on head copy, something I have always struggled with, but am becoming better at.
Our instructor this semester was John, AJ1DM, a CWops member and a great teacher. John challenged us, his students, to come up with weekly GOTA (Get On The Air Goals) to challenge ourselves to do more on air with Morse code each week. The GOTA challenge was useful for me as I no longer feel intimidated by operating CW. I feel comfortable with my ability to copy and send at about 18 WPM, enough so that I don’t hesitate to answer any CQs I hear, and I’m also no longer shy about calling CQ myself.
John was assisted this semester by two assisting advisers, Tony VE2KM and Bruce N9WKE. Tony and Bruce presided over break out sessions and came up with copying and sending games, quizzes and challenges for us.
My fellow classmates this semester were Doug K4LSK, Pat AA0O, Steve KC1EJO, and John, AC2SG.
I would highly recommend CW Academy for anyone who is serious about learning Morse Code and is willing to put the time in to do the work over a two month period. The classes are fun, the work is challenging, and the program absolutely works. And, did I mention? It’s FREE! CW Academy is a labor of love of the members of CWops who want to encourage and promote CW and to help us up-and-coming Morse cuckoos to develop good operating skills.
My interest in becoming a good CW operator is so I will be able to get the most out of operating the QRP radios I have built over the years. When operating low power, good copying and sending skills are much more critical. I think I’m getting there.
This past weekend I was leafing through my logbook and realized that everyone of my 2020 QSOs to date have been CW – I haven’t keyed the mic since last year!
After seeing my OCF Dipole and G5RV wire antennas repeatedly come down over the past 3 years I decided to try something different this fall.
My wire antennas, up around 60′, performed very well, when they stayed up, and I am forever grateful to Bill, W1KKF, who was willing to come out each year with his bow and arrow to shoot the lead lines into my trees.
Knowing that the tops of the trees tended to sway in the wind, I had incorporated strain relief into my subsequent installations by attaching either an inline spring or bungee cord between the antenna end insulator and the rope. Yet, despite these efforts, the antennas continued to come down. Two years ago was particularly brutal when a series of bad storms (including a tornado touching down just south of us) sent large limbs and entire trees crashing down along with my antennas.
So I spent a good bit of time this summer considering and researching alternatives. As all hams know, there is no one perfect antenna and every antennas is a compromise antenna. As a married ham, having an XYL adds an extra level of compromise – her sense of aesthetics. A vertical attached to the eaves like my friend Ed, W1YSM has, or a mighty tower and beam =like my friend John K1LYP has, were both non starters.
I eventually considered trying a ground mounted vertical antenna, complete with ground radials. Our property in Cheshire, CT, includes about 5 acres of wetland beyond our backyard which can’t be built upon. I figured that placing the antenna just beyond the edge of the yard among the trees would be help obscure it, thus making the XYL happy, and the damp ground would also contribute to making a good ground plane.
I first considered a non-resonant 43 foot vertical which seems to have been all the rage over the past decade or so among hams. However as the 43 foot vertical is non resonant on any band, it would require the use of a tuner. Most of the articles I read agreed that the optimum location of the tuner is at the base of the antenna. Such a tuner would add significant cost to the project and its something I was not familiar with.
I next considered the trapped multi-band vertical. I discussed the pros and cons with another trusted ham friend, Steve, K1SKL. Steve told me that his first antenna was a trapped vertical and he assured me it should work well if properly installed.
So after a little more reading and research, I decided to give it a try and ordered the Hustler 6BTV antenna which would get me on 10, 15, 20, 30, 40, and a narrow portion of 80 meters. At the present time (Fall 2019) the antenna alone costs $241, and once you start adding the ‘recommended’ accessories – the price adds up quickly.
In addition to the antenna itself, I purchased the following components, accessories and special tools:
Ground Radial Plate $75
Tilt Base Fold Over Kit $62
Tilt Base Wing Nuts $10
Direct Coax Feed Add On Kit: $30
JetLube Pure Copper Anti-Seize $18
1000′ 14 AWG Copper Wire for ground radials $50
Radial Plate Wire Attachment Kits (2) $18
200 Lawn Staples $32
Guying Kit $34
4′ 4×4 pressurized wood post $13
50 lb sacks of Quickcrete (2) $12
Post hole digger $37
Bow saw for cutting down interfering nearby tree limbs $10
100′ LMR400 feedline $120
When you add in the miscellaneous small parts I needed (replacing hardware I damaged such as over-tightened hose clamps, I was in about $800 – wow, that equates to approximately at least a dozen over-priced pre-fabricated G5RV antennas!
My work on the vertical antenna installation started back in late September. I easily identified a good location about 20′ back into the wooded area behind the edge of the backyard where there was a small clearing bordered by some downed trees and rocks.
Digging the hole for the post wasn’t difficult. Using the post hole digger I bought from the Home Depot made for fairly easy work. I encountered some tricky roots along the way, but none too thick that I couldn’t hack through them. My hole ended up being about 28″ deep.
Setting the post with Quickcrete was a snap too. I started by adding about 2″ of crushed stone to the bottom of the hole for drainage and poured the Quickrete directly into the hole around the post, checking often to make sure it stayed level. Per the Quickcrete instructions I poured about a gallon and a half of water directly into the hole and again double-checked that the post remained level. The concrete set and the post was rock steady by the next morning.
The next step was to attach the DXEngineering radial plate about 2 inches above ground using a pair of lag bolts.
The radial plate has 60 pre-drilled holes to attach ground radials and it was my intent to put in all 60. My first weekend attaching radials, I installed the first 20 radials by crimping the loop connector to the end of the copper wire on site, bolting the loop to the ground plate, and then crawling away from the post, rolling the wire spool outwards, and tacking down the radial with lawn staples as I went. This turned out to be an exhausting way to work, but it did allow me to maximize the length of each of the first 20 radials to fit the space I was installing it, stopping when I encountered a rock, a tree, or downed tree trunk.
I had read that when installing a ground based vertical antenna, the length of the radials isn’t as important as the quantity of radials. For elevated installations it is more important to have radials cut to resonance for specific bands. My first 20 radials measured anywhere from 15′ to 30′ long.
The following weekend brought sub-freezing temperatures and a nasty head cold. So I spent my antenna time working indoors preparing the next 40 radials. These I cut to 15′ in length each, crimped the loop connector, and then coiled the radial carefully so they wouldn’t become tangled. The following weekend I as able to quickly install these radials much more quickly than the first 20.
A few of my crimping jobs failed, so I ended up settling for 50 radials and I subsequently ended up pulling another 3 or 4 from the loop connector when standing on the radials near the post. Next spring I plan to revisit the radials, adding the remaining 10 and repairing any that are damaged to get back up to 60. I will then add crushed stone around the base and covering the radials in order to provide some protection.
Once I was satisfied with the radials, the next step was to attach the tilt over mount to the 4×4 using another pair of lag bolts and the pivot point bolts and lock nuts that came with the antenna. I encountered some difficulty with the one of the nylon lock nuts and ended up having to take a trip to the local hardware store for a replacement.
Assembling the antenna
The following weekend I began assembling the antenna mast in the garage. Assembly was easy enough, however I managed to over-tighten two of the hose clamps that came with the antenna, so this meant another trip to my local hardware store.
Once assembled, I carried the mast out to the base for mating. The 23′ length made it awkward to move, but it wasn’t heavy and actually felt pretty balanced in terms of weight distribution. I used a plastic lawn chair to support the top end of the mast while mating it to the base and then again when folding the antenna over for tuning.
Despite my best estimate of the space needed for the antenna to fold over, I didn’t properly account for 3 gnarly tree limbs that managed to snag the 80M whip when folding the mast over. I picked up a $10 bow saw at the Home Depot and was able to easily remedy this problem this past weekend.
Tuning the traps
The final task was to tune the antenna for each band which is done by loosening the hose clamp at the bottom of each of the traps and sliding the trap downward a bit to adjust for a lower SWR. After each adjustment, I needed to raise the antenna again, take another reading, and then repeat the process until the antenna was in tune for that band.
I used my Rig Expert AA30 antenna analyzer and per the DXEngineering instructions, I started with the 10M band and proceeded to adjust each band in order – 10M, 15M, 20M, 30M, 40M, 80M.
I was able to obtain SWR readings of under 2.0 across most of the bands, which was ‘good enough’ for me given the fact it was below freezing out this past Saturday with a forecast of snow coming. I wanted to be sure I could get on the air before winter fully set in and I planned to revisit the tuning come the warmer weather in springtime.
How does it work?
When I first tried the antenna on the air last Saturday, I was surprised to hear very few stations on 20 M and 40 M. My SWR readings taken at the radio in the shack were also much higher on all bands than observed at the antenna site. Most vexing of all was that I was getting an infinite SWR reading on 20 M! How was this possible???
I decided to not obsess and let the problem go for the night. I returned to the antenna early the next morning to recheck the tuning only to find that nearly all bands were still in tune. (30 M was a bit high in the lower portion of the band than I thought it was the previous day.)
Working logically and through a process of elimination, the next likely culprit would be the feedline. I had purchased a new 100′ run of LMR400 from Quicksilver Radio at the Nutmeg hamfest this fall I had planned to use with the new antenna, but that came up short. I connected it to my existing feedline which ran from the house, underground around the driveway and up to the berm where my previous wire antennas were located. Knowing the new LMR400 should be perfect, I decided to connect it to another 100′ run of coax to connect the antenna directly to the feed point on the house.
That seemed to do the trick.
On Air Success!
After changing out the feed line, I immediately noticed a huge difference on the air. First, there was a lot of activity on 20 M and 40 M, and the measured SWR at the rig was back down under 1.5 for both bands.
I worked KC5SCK in Georgia on 20 M who gave me a 59. My second contact on 20 M was with Belgian Special Event Station OR18TLS (HRH Princess Elisabeth’s 18th Birthday) who also gave me a 59. My next contact was with F5RAG in France who gave me a 55 signal report and my last contact that morning was on 40 M with K0BAK/VE2, a Parks On The Air activation of VE4920 in Quebec. This time my signal report was only 36.
I was relieved that the antenna was resonating and I was able to make contacts and I look forward to getting better acquainted with it in the winter months ahead.
The future and conclusion
When the weather warms next spring, I plan to revisit the installation for some touch up work. My to-do list includes replacing a few of the radials I damaged and installing the rest to get to the full planned set of 60. I also managed to bend one of the hinge bolts on the fold over base (something the instructions cautions you to be careful about) which will need to be replaced. Lastly, I will want to revisit the tuning of all bands.
Overall, this was a really fun project that consumed the better part of two months and in the end my antenna is performing as anticipated. I would recommend the Hustler trapped vertical for any ham who has the time, space and money to undertake the project. It is not a quick installation, nor is it inexpensive. But the project was manageable and even fun and the satisfaction of making contacts with an antenna I assembled can’t be beat.
Have you installed a Hustler trapped vertical? What was your experience like? Feel free to drop me a line at firstname.lastname@example.org.
Have you discovered the wonder of shopping at Banggood or AliExpress? They are both something of a Chinese version of Amazon.com (in fact the Banggood logo is not at all unlike Amazon’s) – online superstores where you can buy a wide variety of products from electronics to clothes to sporting goods to cellphones to jewelry to automotive parts and so on.
The smiling Banggood and amazon logos also feature similar color schemes
One can make several arguments – political, risk, quality – for not purchasing from Chinese online vendors, but I can think of two solid arguments why I enjoy shopping there – the wide selection and the low prices.
Both Banggood.com and AliExpress.com sell several DIY (do-it-yourself) electronic kits – such as radio receivers, MP3 players, test bench equipment, digital clocks, ham radio QRP kits and accessories, etc. The variety is fairly large, especially in comparison to what is available these days from US vendors.
When I was a young scrub, Radio Shack sold a popular line of P-Box (perf-box) kits and I pretty much built all of them including the one-tube AM receiver, the indoor/outdoor thermometer, the shortwave receiver, and the “GoofyLight.”
For the last couple of decades before they folded, Radio Shack did not offer electronic kits that required soldering and several other companies that produced DIY electronic kits, such as Heathkit and Ramsey Electronics have now too either gone out of business or no longer sell DIY kits.
While there are still some excellent smaller scale firms producing mostly ham radio oriented kits today (Four State QRP Group,QRPme, Elecraft), the easy availability to basic electronic kits, like the ones I enjoyed building as a child, doesn’t exist today.
Enter our Chinese Friends
In recent years I have purchased a few DIY electronic kits from Banggood and AliExpress. My experience has been mostly a good one – the kits are crazy cheap, but sometimes the quality of the parts has been marginal at best.
Another problem I have had building kits from China is reading the instructions. English instructions aren’t always included, and when they are the translations are horribly fractured.
The ability to read a schematic can be beneficial, but may not be enough. I have attempted to construct Chinese radio kits where the schematic did not match the PC board and/or the parts provided. I have also been been frustrated at times to find key identifiers for parts like transformers are identified only with Chinese characters on the schematic.
One interesting hack for dealing with a problem with color coded parts such as RF transformers, that I picked up from a shango066 YouTube video, is to reference the resistor color code chart that might be included the instructions. This makes it possible to identify the parts by the Chinese character for the color in order to correctly place transformers on the circuit board.
The Banggood Calculator
Speaking of resistor color codes, what initially attracted me to building this specific calculator kit is that I noticed on the Banggood website that the buttons on this calculator had the corresponding colors of the resistor color code.
The calculator has a mode that will calculate 4 band or 5 band resistor values by entering the color of the rings. (Yes I know that you can easily calculate resistance with the simple table, but this is sort of a cool novelty.)
The calculator has 3 other function modes – basic decimal arithmetic, voltage calculations for LEDs, and decimal-hexadecimal conversion.
One of the great things about this specific kit is that the printed instructions were very good overall and they also included a QR code and the URL for a very well done fully illustrated online step by step assembly guide.
The entire kit took less than 90 minutes to build and I encountered no problems along the way. I did use an ohm meter to confirm the values of the resistors before soldering them in place. The acrylic case went together fairly easily, although aligning the last three screws that hold the LCD in place required a little back pressure with my free hand.
Overall this was an excellent project for a Sunday morning at the workbench and now I have a one of a kind calculator that I can take pride in having built myself.
The only criticism I have about the calculator is that in order to change the two CR2032 batteries, you have to disassemble pretty much the entire acrylic case as there is no battery door. As mentioned above, mounting the LCD screen was a bit fiddly so I hope the batteries exhibit a long enough life.
Overall I would recommend this basic kit for anyone who enjoys building such things.
Have you built any DIY electronic kits from a Chinese online retailer? If so, which ones and what have your experiences been? Please drop me a line at email@example.com.