[600MRG] 630 meter Homebrew

[Dwight Blevins]

I see there's an ongoing discussion on a homebrew tube transmitter for 630 meters. I just built one and it was a most rewarding experience. It was a bit more difficult than I expected, but quite doable for the average ham. Mine is a takeoff on one posted online by a ham in Australia (VK1S?). He used a 6AG7 to drive an 807. I used a 1625 for the final, much the same tube as the 6BG6, 807, 1625, 6l6, etc. It produces about 20 watts output.
Forget the ease of the old 6V6/6L6 style transmitters, which most all of us have tried at some point in the hobby. The high value L/C configurations of the MF/LF spectrum are something located in the pages of another book that many of us have not yet read. Thankfully the online schematic that I found got me in the ballpark, but I still spent several days of cut and try, getting things to gel for my particular setup. I learned some valuable lessons that I'll not soon forget. 

If I had it to do over (and I probably will) I'd have gone for a dual, parallel output in the final. This would produce around 35 to 40 watts out, which, based on my experience thus far, I feel is minimal and needful from a practical standpoint. Many of us do not have a very efficient antenna, so I feel that if you don't have at least something close to a minimum power in the 40 to 50 watt range, then you'll have considerable difficulty making contacts with cw. The challenge might be a little less for those living in areas of high population, but there are just not yet that many hams operating 630m. 

Living in the high desert of western Colorado, it can be a pretty good challenge trying to work another ham beyond the high Rockies to the east, and the Sierra Nevada to the west. Going north and south there are probably at least 100,000 Jackrabbits between me and the next closest 630m antenna. A couple of hams have copied my signal, including KB5NJD, but I have yet to validate a single two-way QSO. 
Am I discouraged? Of course, not. The challenge just enhances the joy of it all! 

To me, 630m is a homebrew tinker's paradise. Right now that's what thrills me the most, so this is where I'll be; pounding the brass and looking for that one and first elusive response to my CQ, which I know lies somewhere on the future horizon. 

Ike, KW7T

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mailman.qth.net/pipermail/600mrg/attachments/20180128/88dd1854/attachment.html>