CW Transmitter PDF Print E-mail
Written by Hans Summers   
Sunday, 19 April 2009 08:14

LETHAL VOLTAGES ARE PRESENT - GREAT CARE REQUIRED!!

This one-valve (ECL82) CW Transmitter occupies a very special place in my amateur radio history. I was first licensed in 1994 but did not operate on air. I committed to only ever operate equipment which I had made myself. I had no time for radio construction and several years passed. In early 2002 I came across a design by Jan Axing, SM5GNN and decided to build it. The transmitter worked first time and tuning was exactly as Jan had said it would be. At the same time, I built a solid state HF receiver using various new and unusual techniques such as a Tayloe switching mixer, Huff & Puff stabilised VFO and polyphase audio phase shift network for unwanted sideband cancellation. My first ever QSO was on 25'th March 2002. Over the next few years I made a number of modifications to the transmitter, and it remained my ONLY transmitter for over three and a half years! During this time I made over 550 QSO's, many of which were long ragchews lasting an hour or two. The little ECL82 valve has served well!


Original version:

The first version was built more-or-less exactly according to Jan's design. A 3.560MHz QRP calling frequency crystal was purchased for the transmitter from the G-QRP club. The chassis was built using unetched single-sided PCB material. The valve came from Jan Wuestens in Germany. Read more...

First QSO:

The first QSO was with Larry G4GZG on 25'th March 2002, over a magnificent distance of 12 miles. At that time the antenna was about 30 feet of wire strung around the attic. The HF receiver was still a loose collection of boards and a mass of wiring. The morse key belonged to my Father. Read more...

Modifications:

If there was QRM or another QSO on my frequency, I had to just wait. I could hear stations on the 3.558MHz FISTS calling frequency, but couldn't work them. I also wanted to be able to work QRP (5W) instead of the full 10W. Finally, I wanted to operate on 40m. Modification time! Read more...

G4KKI 2-way ECL82 QSO!

I made many friends on 80m CW. One of these was Bill G4KKI. Bill credits me with getting him interested again in homebrewing and rejoining the G-QRP club! I sent him my spare ECL82 and he built a transmitter like mine. We had many nice QSO's using the two transmitters, between London and Manchester. Read more...

30m/20m Modifications:

The final set of modifications added 30m and 20m amateur band capability to the transmitter. Yet more relays were piled into the transmitter, to select from the 4 available pi-net coil taps, and from 1 of 8 crystals. A 12-way switch on the front panel selects the desired band/crystal. Read more...

DL9EBA's One-Valve Transmitter:

I had a nice QSO on 80m with Hans-Peter, DL9EBA. Like me, he was using a homemade one-valve transmitter (not the same design as my TX). It uses a Philips EBL21 valve and produces an output of 2W on 80m. It is crystal controlled and also operates on the 30 and 40m bands. The sound was great! Visit DL9EBA's Transmitter page! In German, with pictures, or the English text version.

F6HCC's One-Valve ECL82 Transmitter:

John F6HCC wrote to me, he has built a version of this ECL82 transmitter (click here to read about it). He writes:

"I finished to build the ECL82 transmitter and it transmit very well with abt 8 watts on 80m and 40m. The photos and the drawing are on my site: http://f6hcc.free.fr . I have used and adapted your drawing.

Another Sound Clip of my TX!

Hans-Peter DL9EBA kindly sent me this recording he made. You will hear 30 seconds of my one-valve CW transmitter in operation from my QTH (near London, England), during an 80m CW QSO on 30-Nov-02 with Rene ON4KAR (in Mettet, Belgium). Both stations reported 579 and were using 5W QRP power, G0UPL to a longwire antenna and ON4KAR to a G5RV. The recording from Hans-Peter's QTH in Rheinhausen, Germany was made using the 100Hz mechanical filter of his EKD Receiver. There is some QRM from an SSB USB station on QRG, this allocation is shared with other services at times, in this case most probably Danish fishermen. The preceeding QSO to this one was with Hans-Peter DL9EBA, our second QSO (see his rig above).

This recording can be downloaded in MP3 format by clicking here to visit the web page of Mike Andrews W5EGO. Mike kindly offered to host the files since I have limited space on this server and in any case it does not allow me to host MP3 files. Thanks Mike! Be sure to take a look around the rest of Mike's interesting website.

Last Updated on Monday, 03 January 2011 14:37
 
© 2009 Hans Summers
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