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www.southgatearc.org
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161 km voice-powered QSORadio Amateurs have been experimenting with 'Voice Powered' transmitters, the power comes from rectifying the audio signal from the microphone. Mike, AA1TJ, has now acheived the remarkable distance of 161 km using his 2.5 mW transmitter. Mike, AA1TJ, posted this email, reproduced here with his permission, to the GQRP reflector shortly after completing this remarkable contact: I'm trying to regain my composure here. I just finished a QSO with W1VZR on 75m at ~0500z. Peter is in Limerick, Maine (101 miles/161 km) . It was a cross-mode contact (he was on SSB), although "crossed-up" might be a better description. He sent me a 549 report and I replied with a 57. Once I figured out how to get across my message we both had a 100% copy. The transmitter here is a voice-powered, one-transistor (2N1309, germanium PNP) crystal-controlled oscillator on 3686.4kHz. The "power-supply" /modulator/ keyer amounts to a permanent magnet loudspeaker mounted on the end of an olive can. I've got my nose shoved in this tin-can (smelling olives all the while) and yelling for all I'm worth. The output power is in the vicinity of 2.5mW with peaks as high as 12mW. It was supposed to be AM; only, Pete remarked right away that it sounded more like a dog barking (I'm wiping away my tears as I write this :o) He had plenty of signal but my intelligibility was very poor. I started swapping in a modification that I'd found in an early 1960's Italian radio magazine. Please see "IL Baby Signal" starting on page 40. The mod consists of transistor TR1, R1 and R2 shown in the schematic of page 41. So, I'd put the mod in and yell, "I'VE MADE THE ITALIAN CONNECTION!" (followed by a laughing spell). Pete thought it helped...sez I went from sounding like a dog to sounding like a seal. That's when I started yelling "DIT DAH DAH...DIT DAH DAH DAH DAH," etc., and Peter came back saying he had a perfect copy and gave me a report (notice, he gave me a "CW" report). I came back with his report. He returned saying that he copied it all and relayed it back, word for word, "R R FB PETE FB 57 57 57." Exactly! So that's it...an honest-to-goodness, voice-powered, QSO at a distance of 161km! Aside from the modulation, my biggest problem was that I couldn't stop from laughing. And it got worse every time Pete came back on account of he's such a joker. He heard my final transmission just as clearly, including the last "Dit Dit Dit Dah Dit Dah.....Dit Dit." He came back to that just about in hysterics. Hmm...did I just break the rules? A2A, or tone modulated CW (MCW), is verboten; whereas, I was speaking the words "DIT" and "DAH." On the other hand, I don't think I was AMing well enough to call it A3. Pete copied me with his BFO on, so it was probably more like voice-keyed CW (I remember seeing something in an old "Hints and Kinks" about a breath-operated keyer). The difference here is the vibrations set up in my vocal cords not only keyed the CW transmitter it provided all of the energy to run it as well. Truthfully speaking, it was modulating to some degree. On the other hand, it was so much fun that I'd do it again, even if I had to swing for it. :o) I just got off the phone with Pete, only, I don't think we actually said much of anything. He played a recording that he made of my signal back to me over the phone, and then we just spent the rest of the time laughing. Pete says it was his first ever QSO with a seal. Oh man...I'm still wiping my eyes here. I'm starting to get a reputation. When I make a CW transmitter it sounds like a bird. I try to make a phone rig and it sounds like a dog, unless you think it's a seal. Right, so I've got to do work on that modulator. Oh yes, I'm going to call my new lung-powered transmitter "El Silbo." Some of you may recognize Silbo as the whistled language (of sorts) that's used on the isle of La Gomera (Canary Islands) to communicate across wide mountain valleys. The best DX is apparently around 2km (or is it 2 miles?). At any rate, you can see some examples on these links. http://news.bbc.co.uk/1/hi/world/europe/3241128.stm One more thing. The receiver I'm using is a one-stage regenerative detector built around a second 2N1309 germanium transistor. The collector supply voltage is 250mVDC. That's right...a quarter of a Volta (look how I'm talking Italian now). The eventual goal is to power this receiver from a distant commercial broadcast radio station by rectifying the RF present at the receiver antenna input terminals. In other words, "RF energy harvesting." The detector will oscillate down to 180mVDC, only, I haven't gotten around to hooking it up to an off-air detector. I just used my bench power supply for my contact with W1VCR. Again, I had a perfect copy of his 20w SSB signal. What a riot. Cheers, Mike, AA1TJ
GQRP Club GQRP Yahoo Reflector Mike Rainey AA1TJ
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