My first Pixie SOTA experience

On Friday, February 6, I made the decision to hike on Saturday, February 7, to SOTA summit EA5/AT-099, Serra Mitjana, with a 7023.2-kHz 0.3-W Pixie (which I bought pre-assembled from a Chinese online shop for about 8 euro) and a center-fed half-wave inverted-V dipole. 

COVID-19 regulations in force restricted me to summits inside my municipality (Alacant). There are two; the other one is Fontcalent, EA5/AT-036, which is a harder climb. I had already activated Serra Mitjana three weeks ago (never activated before) with my Xiegu G90 and a whip antenna, but I thought it was better to hike to a known summit for the Pixie experiment. And this one was great to spread a dipole, nice and flat at the 407-meter top. No trees, though, so I was expecting to keep the mast up using the two branches of the dipole and the feedline in a triangular configuration.

My plan was to be there at around 0900Z, but I arrived a bit earlier, around 0815Z, after a rather leisurely 25-minute hike from where I parked the car, about 30 minutes from home. It took me a little time to erect the dipole without fixing the mast (a telescopic, 5-meter fiberglass fishing rod — but I didn't use the last meter or so, too thin) to anything, but I was lucky that there was no wind at all and it nicely stood up during the whole activation.

I knew that receiving with a double-side-band conversion receiver with no audio filtering such as the Pixie was going to be tricky, as would also also hear operators in a wide, 6 or 8 kHz band around the beat-frequency.

I calibrated the Pixie at home, using my IC-725 and a NanoVNA to generate a fixed-frequency carrier (I also found that my IC-725 was some hertz off on the way). Its transmit frequency was 7023.2 kHz. I marked the dial (that changes the frequency of the beat oscillator by about 1.5 kHz), and made a small mark where I would comfortably hear a 850 Hz tone from stations that zero-beat me. Of course, I would also hear stations 1700 Hz above, but moving the dial and checking how the tone changed would tell me.

By the way, another nice (but laborious) way to calibrate it is to listen, pick up call signs, zero-beat them, and then check frequencies in a cluster or the Reverse Beacon Network which automatically spots CW, bearing in mind that you hear stations on both sides of the BFO frequency. A tuned music keyboard and a list of frequencies can also provide audio frequencies to compare with what one hears.

To power it, I used a pack of 2×3×4,5 V batteries that I had prepared for a different purpose. I'm sure it would have worked as well with just 3×4,5 V, at half the weight. To listen in, I used a foldable AKG headset.

I spotted myself using the SOTA Spotter application on my mobile phone, called CQ SOTA very slow, and colleagues started to reply, even pile up. I had a hard time picking them up from all the other stations in frequencies around (but not as hard as I expected), and (as usual) made a bit of a mess of the pile-up. I ended up logging 7 QSOs, EA and F, between 310 km and 780 km away, with very understanding colleagues:

08:44	EA2DT
08:50	F5JKK
08:52	F5LKW
08:55	EA2EOW
08:58	EA3AVV
09:02	EA7GV
09:27	F4WBN
09:28	EA2IF

To make things worse, my antenna connection was a bit flaky (it had desoldered, as I found when I came back home), and I did break my 3D-printed Chinese key at ~09:40Z, which ended the CW part of the activation.  Clearly, I was hitting it too hard, and perhaps part of the chirp was due to a bad contact. I also lost one of the lenses off my glasses, but that is not a radio-related incident (I searched for it for about 45 minutes while doing some 2m FM QSOs with my FT-60, no luck).

F5LKW Roger, a triple SOTA goat (>3×1000 activations!) was so kind that he even put together a nice video of part of my activation (https://www.youtube.com/watch?v=ebwHqVjcjYQ) which clearly shows the mess I made but also the terrible chirp I had.  Roger had already done a Pixie activation himself in 2017 (pictures in https://sotl.as/summits/F/AM-694). 

The take-home (or take-to-the-summit) message? If you're lucky and your Chinese Pixie works well [1] (which you can test and calibrate at home), bring a nice straight key, batteries, headphones, and a proper half-wave dipole to a summit, and you might be surprised at what you can do.

[Edit, March 17, 2021: lots of people have taken their Pixies to SOTA activations. According to the spots posted on Twitter, about 40 people have self-spotted themselves activating a summit with a Pixie]

[1] The pixie I brought to Serra Mitjana was the second Chinese Pixie I had bought. The first one worked but came with a broken 47 kΩ BFO potentiometer. Having no replacement for it, I removed the potentiometer, and installed two resistors I had (22 kΩ and 33 kΩ) instead, to simulate it being roughly half way. Its RX frequency is 7023.68 kHz, 540 Hz above the TX frequency, 7023.14 kHz. A tone of 540 Hz when a station zero-beats me (chirp allowing) is a bit 'bass' but should work. One problem, of course is that I will hear an operator at 7024.22 kHz ("image") with exactly the same tone. With a variable potentiometer, moving it a bit clearly shows which one is the right one; with fixed resistors, one has a 50% chance.