Parasaki

Yesterday I received the schematic of a very remarkable transceiver in an e-mail from Peter DL3PB.
The Parasaki transceiver is an all diode receiver which is built with tunnel diodes in stead of the usual transistors. Peter proudly said, that a long cherished dream came true, after 40 years, to build and operate a transceiver build with tunnel diodes.

But that's not all. After completing his temporary antenna, Peter heard the very, very strong signal of Christophe F8DZY, in the France REF contest. When Peter answered his CQ, he got an immediately correct response, although his power was only 2 milliwatts. hi

Parasaki Transceiver Power 2 milliWatt  Peter  DL3PB

This is what Peter wrote in his first e-mail:

Hi folks,

I'd like to share with you a long-cherished dream, that recently came true, fourty years after I came to read about hams using tunneldiodes to make QSOs when I was aged twelve or so:
Finally I managed a first skywave QSO with my PARASAKI-transceiver, an 'all diode' rig:
Christophe F8DZY replied to my very first call on 20m band in REF-contest last weekend.
I was running 2mW into a temporary vertical dipole on my balcony. Distance between us is 918km - obviously OM Christophe has excellent ears.
Those interested in the cruel details of my circuit, please find attached a schematic and a photo of the pretty ugly setup. The circuit is designed straight-forward with exception of the parametric VXO, derived from Mike/AA1TJ's famous Paraceiver design. (see http://fhs-consulting.com/aa1tj/paraceiver.html )
The low impedance of the high peak-current tunneldiodes make it very difficult to built a really crystal controlled oscillator rather than an LC-oscillator, synchronized by the crystal more or less, at least on the higher SW-bands. The Parametric VXO provides a crystal-stable, chirp-free signal on expense of an output power of two milliwatts only instead of ten, but with an amazing spectral purity, no need for a low pass filter or such.
Of course it sounds pretty cool making a QSO with a 'bunch of diodes' and a parametrically excited crystal, but believe me or not, I'd preferred to bring that full ten milliwatt into the air - on the other hand that approach allowed to tune the rig a bit ( ~ 5kHz/per xtal ), which turned out to be much more valuable than a few milliwatts more while being 'rock-bound'.
The receiver in its 'gain-less' version works fine for strong signals - while listening to QRP(p) stations, the moderate gain of the audio amplifier helps a lot. A comfortable frequency shift between receive and transmit is realized by the 5µH inductor at the LO-port of the mixer, with little effect on sensitivity.
Thanks for the bandwidth, OMs, won't bother again you with such mails, unless I make a cross-pond QSO with that rig ( not that likely ) or any skywave QSO with homemade semiconductors ( probably impossible )...
72! Peter/DL3PB

In my answering e-mail I said:

As a milliwatt enthusiast my self, I know the thrill of making contest QSO's with a few milliwatts. Your 2 mW reminds me of the QSO's, I made in 2001 to 2003 with 2.5 mW to 10 milliwatts in many different contests.
It is amazing what a "simple" circuit like this can do. I like the set up on these experimenting board. It's great fun. I think you made an excellent choice to choose for "broader" tuning range. But "on the edge" a few dB can really be helpfull. hi
Yes, Christophe must have excellent ears. But with so little amplification in your receiver, you also must have excellent ears.


The next day Peter replayed with:

Hello Bert,
when I actually had set up my antenna last saturday and while adjusting my rig,
I heard F8DZY call CQ test - he was really booming in, and I recalled your strategy, to monitor the signal strength of the incoming signal in order to find the best time for a call.
I have no S-meter, but he was peaking such, that I was sure that couldn't last for long - so decided I'd better give him a call immediately rather than trying to squeeze the last tenth of milliwatt out of my rig - so I did and before I could repeat my call once more, he came back with my callsign and the department number - so it payed off to study your miliwatting results carefully!
Sensitivity of the receiver is not that bad, given the low part count - with the audio amp and a sound powered' headphone I can copy EU-QRP stations pretty good. Of course that won't work with a TV playing in the background, but I'm blessed with a wife, who is willing to use headphones on occasion.
Thanks a lot, Bert, please keep up your great blog!
Peter/DL3PB

Congrats Peter, on your great achievement!

Click here to go to Roger G3XBM's Amateur Radio Blog for
more info on the Parasaki transceiver.

Click here to go to SolderSmoke Daily News for
more info on the Parasaki transceiver.