AA1TJ - fit and well

This afternoon I got an email from Michael Rainey AA1TJ.  It sounds like they have just emerged from a long crisis with his partner's health and things are getting back to normal after a long, hard, time. I am so pleased.

AA1TJ Mike Rainey

Often it is some time before you realise someone is not around. You just realise they are not there. Often there is a simple explanation, but you are never quite sure. Are they away on a long trip,  have they lost interest in the hobby, have they been, or are they, seriously ill or have they died?

Yesterday, I sent Mike an email asking him for just a quick ping back, but nothing was heard. This afternoon I contacted some of his friends in the USA hoping they have some news.

If you know what has happened to Michael Rainey AA1TJ, please let me know.

Michael Rainey AA1TJ

Overnight I had a very good email from Michael AA1TJ. I was so pleased to hear that both Michael and his XYL were well and he is still busy with QRPP. 

Some of his results are truly inspiring, as they usually are!  In my view Michael is one of the most amazing QRPers on the planet and he definitely has produced some really great design ideas over the years.

Marconi pre-WW1 radio station

Michael Rainey AA1TJ's Facebook page has this photo of a very early Marconi radio station on Cape Cod. 

By the First World War it was already old technology. 

Crystal set sensitivity experiments

This afternoon I had a little play with a simple crystal set to see what sort of minimum discernible signal (MDS) was possible. My previous experiments with single germanium detectors had yielded an MDS of around -55 to -57dBm in the 5-30MHz range with a high impedance crystal earpiece.

Today I tried the same test with both germanium diodes and a hot carrier diode (HP2835) with and without some bias applied to the diode(s). Best results were with the HP2835 and with about 0.11V forward bias applied. Only a few uA are needed so battery drain is next to nothing. MDS was around -62dBm for a well modulated AM signal. For the tuned circuit I used a T50-6 toroid with around 20 turns with an antenna link winding adjusted for best sensitivity/selectivity and a 365pF variable capacitor .

Incidentally, forward bias for the diode could be obtained by rectifying other signals available on the antenna such as MW/LW broadcasters using a separate tuned circuit, rectifier and reservoir capacitor. I must give this a try sometime. Several hundreds of mV DC should be possible.

Then I tried switching the diode with a second signal generator at a power of between 1-10mW to see what sort of sensitivity could be obtained on a CW signal. MDS improved by around 25dB to around -86dBm i.e. I could just hear down to around 10uV. This would be a just usable level as a basic HF SSB/CW receiver.

I also tried the same tests with a pair of high sensitivity ST-3 headphones that Michael AA1TJ kindly managed to find for me. These are much lower impedance than the crystal earpiece so I experimented with antenna match and the match of the diode to the tuned circuit, expecting a better performance at the best settings. Disappointingly, the results were several dB worse than with the crystal earpiece.

Now, the results with the crystal earpiece are very close to those (without bias) that I obtained some years ago, so I don't think my hearing (at 63 years old) has changed much for the worse. So, Michael must have incredibly sensitive ears as there is no way I was able to hear down to the levels he could with his passive receivers.

At the moment I am playing with the AM crystal set with -62dBm sensitivity listening to shortwave broadcasters. Fun.

QRP at AA1TJ

It's time to remind people of the wonderful circuits and ideas at Mike Rainey AA1TJ's site. Always full of amazingly simple designs that really work. See  http://www.aa1tj.com/radio.html

From Michael Rainey's blog

http://aa1tj.blogspot.com/2010/09/verweile-doch-du-bist-so-schon.html

Michael Rainey AA1TJ has an excellent blog in which he covers a range of subjects. This post (see link) is about a tiny pocket watch made almost entirely from wood and other organic materials that Michael came across in a museum in Vienna.

Another beautiful QRP transceiver from AA1TJ

Menos es MAS is another fine QRP transceiver design from Mike Rainey AA1TJ. This really is about as simple as an HF transceiver gets with reasonable performance and QSOs in his log to prove it.  I like Mike's technique of using a development board to knock circuits together. This approach is fine for lower HF bands.

AA1TJ's success with the XBM80-2

Mike Rainey AA1TJ has built his version of the XBM80-2, but LESS the audio stage, using instead his 600 ohm magnetic headphones via a transformer, and has managed some QSOs well over 100 miles. He changed the emitter resistor to 15k to reduce the signal radiated on key-up (backwave) as well as made a link coupled bandpass filter output/input circuit. This would reduce the amount of AM breakthrough usefully.

Voice powered transatlantic 20m test

AA1TJ's historic attempt to span the Atlantic with just a "voice powered" TX (powered only with DC generated by rectifying audio from a LS into which he was shouting) started at 1500 UTC on Tuesday Nov 10th. Power out was about 15mW QRP from the coast of Maine, USA. They had a 2el vertical antenna aimed at Europe and a good clear sea path, but unfortunately the test was unsuccessful, although they did make contact (not voice powered though) with Europe on 160m QRP. For a report see http://www.QRPme.com .

More voice powered DX in the USA

Mike Rainey AA1TJ has pushed his DX up to 1329kms on 80m using his Code Talker TX (see left) which uses only the energy derived by shouting into a loudspeaker to power the transmitter - no external DC power sources at all. He worked W4OP at 0133z. Just visible is the tin can used to focus the shouts into the LS cone! I am beginning to think Mike will work some serious DXCC countries in the years to come using his "voice powered" TX. Imagine this rig into a beam on 10m when the sunspots are high.

Mike tells me he is having a go at a 20m version now.

AA1TJ's Code Talker TX

Mike Rainey has now added a schematic to his page on the New England Code Talker CW transmitter powered and keyed only by audio derived from his whistling into a loudspeaker. Mike is hoping to span the Atlantic with a similar TX on one of the HF bands in the years to come, knowing that others have "crossed the pond" with powers as low as 1mW or less when conditions were very good.

AA1TJ's "Code Talker TX" - all voice powered

Mike Rainey continues his work on purely voice powered transmitters, in which just the energy in his voice is used to power the RF circuits i.e. no batteries or PSUs at all. He's achieved well over 100kms on 80m this way using a form of CW derived by whistling into a loudspeaker to generate the energy needed. Here is an example of his signal received 109kms away. He can clearly be heard "keying" (actually whistling!) the words of "Mary had a little lamb" in CW.

AA1TJ's Voice Powered DSB TX (El Silbo)

Mike has done it again - a superb piece of QRP creativity. This is from his email today:

"AA1MY and W1PID met with me on 3686kHz this afternoon. I was operating a new, DSB version of my "El Silbo," voice-powered transmitter. Both Seab and Jim successfully copied my/their calls and signal reports. Jim commented later that I would have been hard pressed to pick a worse day for the attempt. The propagation was producing severe QSB fading and the QRN was all over the place (peaking at S-7 to S-9 at times). I came away nearly dumbfounded that these two operators could pull enough of my 5mW DSB signal out of the mess, at distances of 100 and 67miles, to complete the QSOs."

Lambda diode circuits

Mike Rainey AA1TJ has some good tunnel diode ideas on his pages but these devices are hard to find these days. Instead one can create a negative resistance device called a Lambda diode with a couple of FETs or an FET and a transistor. See for example the pages of Ramon Vargas Patron at http://www.zen22142.zen.co.uk/Theory/neg_resistance/negres.htm where he has examples of oscillators and regenerative receivers using Lambda diodes.

161kms voice powered QSO by AA1TJ

Just got an email from Mike Rainey AA1TJ describing his TX powered only by his voice. He achieved a distance of 161kms with a germanium transistor oscillator putting out a few mW of power. The power for this was generated by rectifying the audio signal from the loudspeaker used as a microphone. In the end Mike resorted to a sort of MCW mode shouting CW into the LS but W1VZR copied this and made a recording. Mike is also looking at a receiver using "RF harvesting" to allow a receiver that requires no DC power source other than that derived from off-air RF.

Mike's amateur radio pages are at http://mjrainey.googlepages.com/radio

AA1TJ's 1 transistor transceiver

Take a look at Mike's neat 1 transistor VXO controlled 80m 80mW transceiver, The Reggie, which uses a passive RX with the VXO acting as LO for a heterodyne mixer. He's worked some decent distances with this modest little rig. Mike has a great website with plenty of other fine ideas. The little Reggie circuit continues to evolve so keep checking back to his site.

http://mjrainey.googlepages.com/reggie

Update 19/1/09: Mike tells me he has measured the MDS as -87dBm (using a sig gen and a stepped attenuator/20dB pad) which is pretty remarkable for essentially a passive RX using a switching mixer. It implies Mike can hear around -90dBm clearly in his ST3 headphones.

Tunnel Diodes rigs

Way back in the 1960s I recall making a simple tunnel diode oscillator as part of a lab project and being excited to see such a circuit used to span 160 miles on 80m by a ZL station despite the power being microwatts only. These days tunnel diodes are almost unheard of.

Recently I spotted a similar tunnel diode TX and RX on AA1TJ's excellent webpages on which you can find more data and links to off-air records made at DX distances.