Tag: POTA

Multi-frequency modified QRPKits.com Easy Transmitter

This weekend I returned to a shelved project from several months ago, a complete 40 M QRP station built around the Easy Transmitter & Easy Receiver kit line from Pacific Antenna (QRPKits.com).

Why the Basic Pacific Antenna Kits?

I first became aware of these excellent basic kits a few years ago when we chose the Easy Receiver kit as a group build project for a Wednesday Workshop at the Yale Center for Engineering Innovation and Design that we, W1YU, the Amateur Radio Club at Yale University were hosting.

The CEID is a nicely equipped maker space at Yale and their Wednesday Workshop series allows students, faculty and staff to learn something new by making. Popular Wednesday Workshops have included chocolate making, woodworking, 3D printing and W1YU would program a workshop to introduce the uninitiated into radio fundamentals.

We chose the QRPKits.com 40-meter direct conversion receiver for one of our workshops because the kit was simple to build and able to be completed in less than two hours, was inexpensive, and had a reputation of working the first time. That night 20 CEID members, most of whom never soldered before, paired off into 10 teams and after a presentation on RF and a brief soldering tutorial, they got down to work. I’m very pleased to say that out of 10 kits attempted, all 10 worked, with only a couple needing nothing more than a touch up of a cold solder joint or two.

My Current Project

My initial plan was to build the Easy Receiver and Transmitter and mount them into a single enclosure (a cigar box) to make an all-in-one station. In addition to the receiver and transmitter, I had also planned to incorporate the Easy Audio Bandpass Filter, the Easy TR switch, and the Easy Low Pass Filter to limit out-of-band harmonics on transmit.

I had assembled all of the basic kits several months ago and as I often do, became sidetracked and never finished the project. I came across my circuit boards recently in my basement workshop and decided to pick up from where I left off.

I had previously completed the receiver, audio filter, TR switch and the low pass filter. The transmitter was still in its original packing, so this became my first project for the new year.

My completed 40M transmitter with rotary crystal selector and fine tune control.
The completed project delivers 2.0 watts on all five frequencies.

A Couple of Modifications

I mentioned I came across the unfinished project in my basement recently. Over the past several months I have been working on organizing my workspace including inventorying and sorting the myriads of components I’ve managed to stockpile over the years. One of the things discovered in doing so was a variety packet of 40 and 80-meter HC-18U crystals for the QRP experimenter.

I decided I wanted to modify my transmitter build so instead of just being limited to the 7.040 crystal that came with the kit, I could easily select a different frequency by swapping crystals. The kit itself makes a provision as it includes a socket so the builder/operator could plug in a different crystal if they wanted to change frequencies.

My modification takes the concept a step further. Creating a small bus board on which I mounted several crystals and connecting one end to a rotary switch, I was able to make changing frequency as easy as twisting a dial. My transmitter allows the operator to quickly choose between 7.030, 7.040, 7.055, 7.110 or 7.118 MHz.

I made two other minor modifications. I incorporated the low-pass filter on board in the transmitter cabinet instead of as a stand-alone accessory, and I also added a yellow LED coupled with a 1K resistor to provide a power on pilot light on the front panel.

The green PCB is my multi-crystal mod. One side of the crystals are tied together and connected to the crystal socket on the main board while a ribbon cable connects the other sides to the rotary switch below.

I used a small Nub cigar box for my cabinet. I sanded off some printing on the bottom surface and applied a nice cherry stain to the box. Orienting the box so I used the thin bottom as the front of the radio, I had no problem with short potentiometer shafts. The sides of the box were quite a bit thicker, however, and I needed to countersink the holes drilled for the SO239 antenna connector and the coaxial DC power socket.

Another nice feature of the Nub box is that it has a slide off lid, which now becomes the back panel of the radio. It makes for easy opening for repairs or adjustments – or for show and tell at the local club.

How does it work?

The Easy Transmitter Kit promises 2 to 2.5 watts output on the 40-meter band, and I am very pleased to report that indeed, I measured a solid 2.0 watts on all five frequencies. The circuit includes a 5K potentiometer for fine tuning which allows a band spread of a few kHz. For the four lowest frequencies, I spotted my signal right on frequency with the fine tune knob set dead center. 7.118 was a bit off center, unlike the others, but still solidly within range of the fine tune control.

Needless to say, I was very impressed with the initial performance of the transmitter the first time I powered it up.

What’s Next?

I mentioned that I have already purchased and assembled the other kits in the QRPKits.com “Easy” line. I plan on mounting the 40 meter Easy Receiver and the Easy Bandpass Filter in two separate but matching Nub cigar boxes. I plan to mount a speaker in bandpass filter cabinet and include a headphone jack, and to not include any speaker on the receiver. I plan to either use the receiver with earphones (my preferred means for operating CW) or will use a 3.5mm jumper to feed the bandpass filter/speaker unit.

I am contemplating building a small linear amplifier to give myself a boost as needed. QRPKits.com and QRP-Labs.com each offer a simple RF amplifier at a low price that promise to boost 2 watts into the 7-10 watts out range.

I highly recommend the QRPKits.com Easy series of kits for the aspiring kit builder or the old timer, like me. As priced, they remain a great value, and the kits are easy to assemble and best of all – have always worked as advertised.

I plan to blog about the matching receiver and audio amp/bandpass filter as I manage to complete those projects. Have you built any of the QRPKits.com kits? What was your experience? Drop me a line and let me know how you fared at james@ab1dq.com.

Thanks for stopping by my blog & 73!

A peak inside – the auxiliary low pass filter was mounted to the side just above the S0239 connector, using a mounting screw from the S0239 and a modest amount of hot glue to hold the board in place.

©2025 JMSurprenant & ab1dq.com.

Yosemite National Park

POTA K-0071 – 13 FEB 2023

This past week I had the opportunity to glom onto a business trip my wife was taking to San Francisco on the cheap. As her travel and lodging was being covered, I was able to enjoy a mini-vacation for the cost of an airplane seat – not too shabby!

As we have visited San Francisco a couple of times in past years, and despite the fact we never tire of the “City by the Bay,” we thought it would be fun to do a side trip to Yosemite National Park, which I had not previously experienced. It is a four hour drive from San Francisco – but a scenic one.

I realized this was a pretty good opportunity to practice my POTA activation skills and to test some of my new gear including the End Fed Half Wave antennas I recently constructed. I’ve never flown with more ham gear than an HT or two in the past, so going through TSA with a complete HF go-bag was going to be a new experience as well, one from which I learned a few things.

Packing for the trip

I decided that my Xiegu G90 DSP transceiver would be a good choice to fly with as it is compact and although it only puts out 20 watts, it should perform well at the higher altitudes found around the edge of Yosemite, even on SSB.

I packed the G90 in its original box, which not only provided protection for the rig with the Styrofoam inserts, but it also provided enough space to tuck in a mini un-un, some power cables, a copy of the manual, my mini log book, and a pencil.

I printed an official copy of my FCC license and included that as well in the G90 box and, using a Brother label maker, I labeled the outside of the box, “Property of Amateur Radio Station AB1DQ, Cheshire CT.” While based on the accounts of flying with ham gear that I read that others shared online, I didn’t anticipate much difficulty going through TSA with my shack-in-a-bag, but I felt a professional looking packing job might be useful if any TSA agent asked hard questions.

Originally I planned to power the rig from the rental car battery, I made two sets of power cables that terminated in PowerPole connectors that interfaced with the G90 power cord. One set had battery post clamps to attach directly to the car battery, and the other had a 12 volt cigar lighter plug. Based on the 8 amp rated current draw of the G90 at maximum 20 watt output, I felt I didn’t run much risk of blowing the 15 amp cigar lighter fuse, but I did pack extra fuses just in case.

Then I decided for not much more space (but a bit more weight) in my go bag, I should bring a LiFEPO4 battery and charger which would allow me more flexibility to operate, should I want to, after we returned the rental car for the San Francisco portion of our trip.

I found a deep cycle 12Ah 12.8 battery on Amazon that met my specs for less than $60. I made a short jumper cable terminating in PowerPole connectors which I pre-attached to the battery. Like the rig, I kept the battery in its original packaging in my go-bag, again labeling the box with my callsign and contact information. The battery did catch the attention of the TSA agent, but after a careful visual inspection, she returned it to its box and handed it back to me.

My antenna plan was to use an End Fed Half Wave. A couple of months back I built a pair of 49:1 un-uns from HFKits.com, and had yet to try them out on the air. This seemed like a great opportunity, so I packed both along with 60′ length of basic hookup wire to use as the radiating element.

I have been one who has always struggled with launching lines into trees for my wire antennas, so after some YouTube research, I thought I’d try something new. – an arborist throw-line attached to a 12 oz weight. Given the altitude of the park’s rim from where I planned to operate, I didn’t need too much height for the antenna, The 20-30′ or so I could get the high end up in a sloping configuration should suffice, so the throw-line seemed like a promising option.

I found just the thing again on Amazon, and I also decided to add a collapsible throw line storage cube, which would allow me to keep the line untangled during transport and deployment. The cube was great because it folds flat but its 16″ square sides meant that it would not fit in my duffel bag go-kit, so the throw line and storage cube would have to be packed into my checked suitcase. The flatness of the collapsed cube made it easy to pack at the bottom of my checked full size suitcase along with my clothes for the trip.

I used a couple of gallon size Ziplock bags to pack the miscellaneous items I would need, including my Morse key, 60′ of antenna wire, additional pencils and a pencil sharpener, a couple of power cable extension cords, etc. All items, aside from the throw line and cube, fit nicely in a small duffel bag along with my laptop, a couple of books and a few other carry on items for the trip that would stow nicely in the overhead bin.

Aside from the visual inspection of my carry-on bag by TSA, with the careful attention given to the battery, I had no problems taking the go-kit through airport security and onto the plane. I wasn’t asked any specific or probing questions about the contents of my bag.

Operating Yosemite

We were staying at the Yosemite Valley Lodge while in the park, which we found to be great accommodations for our visit. However, being deep in the park valley, with rising mountains on all sides, it made sense to find a spot from which to operate that was higher up off the canyon floor. And, while I’m aware that a big part of the POTA program is to present ham radio in a positive light to the uninitiated, and as much as I love being that goodwill ambassador for our hobby, I tend to get nervous when I’m being watched, particularly when I’m not completely familiar with gear or a configuration I haven’t tried before. So I was also looking for an operating site that was a bit more remote with less foot traffic.

After studying a map of the park, I decided a good bet would be to drive west up Big Oak Flat Road towards Porcupine Flat which was north of us and had a picnic area. However, the Tioga Road is closed in the wintertime, so we ended up stopping near Toulumine Grove at the road closure.

There was a convenient parking area there at 37-706250 N, -119804167 W which provided both altitude and minimal foot traffic. The spot looked ideal for my planned activity so I parked the rented Ford Edge and began my set up.

This was the first time I tried a throw-rope and I found the deployment to be about as easy as it seemed in the YouTube videos I had watched. However, due to some chronic shoulder pain I’ve been experiencing in my right arm, I have been lacking my usual range of motion and wasn’t able to get the bean bag weight over my chosen branch, but needed to settle for the next one below, which I estimated to be about 20′ up.

I detached the throw weight and connected the the end of my 60′ antenna wire to the rope and hoisted it up to the branch and tied the throw rope to the trunk of the tree. I asked my wife to stretch out the sloping antenna wire to the point where it met the ground and I repositioned the car.

I attached the end of the antenna wire to the un-un and connected the un-un to the G90 via a 25′ length of RG58. The antenna was sturdy and up high enough that any passersby should not run into it, but I realized after the fact that I failed to make appropriate use of the strain relief on the un-un. (See right most photo below for how to do it right!)

While I should have taken the time before flying off on my trip to test and trim my wire element to obtain a minimal SWR, I didn’t have the opportunity to do so, but I was pleased that the G90’s auto tuner was able to obtain a 1.8:1 SWR.

Initially I powered the G90 via the cigar lighter plug I fashioned, but found the voltage reading on the G90 panel to be right around 11.0 V. Upon switching to the LiFePO4 battery, the G90 was reading around 13.0 V. so I continued to use the battery.

The immediate advantage to operating (very) remotely and on a battery, is how quiet, nay, silent, the HF bands are. A far cry from the noise floor that is typical at my home QTH fixed station.

I began calling CQ POTA on SSB on 14.324 and over the hour I had available to operate that day, I made 11 contacts. Fewer than I had hoped for, but enough to make my activation successful.

With my 20 watts and a wire, I worked as far north as NL7V in Fairbanks AK who rated my signal 53, as far east as K9ICP in Greenwood IN who reported my signal 59, and as far south as W5NM in Las Cruces NM who provided a 55 report. Included in my 11 contacts was a single Park-to-Park contact with K7CAN who was activating Minidoka Internment National Historic Site, Park K-0849 in Idaho. We swapped 59 reports.

Lessons Learned & Conclusions

I mentioned due to our compressed travel schedule, I only had about an hour of operating time, but it didn’t matter as I had a great deal of fun. This was only my sixth activation in over two years, so I’m still very much green and learning.

The positive takeaways from this trip was I learned how to effectively and efficiently pack an HF go-bag for air travel, and while I will need more practice, I did successfully and quickly deploy my EFHW antenna with the arborist throw line.

Areas for personal improvement include the proper testing of new gear at home before traveling to a park. I shared that despite not testing my un-un and antenna prior to traveling, I had an adequate SWR once on site. (I did bring extra wire and a pair of nippers in the event my SWR was so far off I needed to do major mods on site.)

Finally despite the entire station fitting comfortably in my go-kit duffel bag as carry -on luggage, the bag was pretty heavy and given my shoulder pain I mentioned above, it was a bit uncomfortable to lug through the airport and stow in the overhead bin. Thus, I splurged and stopped at a UPS store to have the radio and battery shipped home to me so I didn’t have to fuss with the weight or the TSA on the trip home. That ran me about $60 for packing and shipping, but the gear did arrive home safely.

Finally, I’m planning on issuing QSLs to all stations I worked during my POTA activation. I still love collecting cards and am one of those old-school hams who hangs wallpaper. I had sent out cards for some of my previous activations, primarily to ops who indicated they were welcoming of receiving cards and would reciprocate.

I’ve designed a commemorative card for my Yosemite activation and will be printing the cards at home on card stock.

My ham resolution for 2023 is to get on the air much more than I have in recent years and I’m planning on making POTA activations a major part of that goal. The Yosemite trip was a great, albeit limited experience, that helped me build confidence and comfort.

What suggestions, thoughts or ideas do you have to share that I and others may use as we take to the parks with our rigs? Do you have a memorable POTA experience to share? Feel free to add a comment or contact me directly by email at james@ab1dq.com.

73 & thanks for reading!
James

AB1DQ, James & XYL Ellen, at the Tunnel View Scenic Overlook in Yosemite National Park, February 2023. This photograph was taken by a charming young Ukrainian woman we met at the overlook. She shared some of her story of the affect the Russian invasion has had on her and her family and we had the opportunity to express our heartbreak and our support for her people.