May 4th 04, 05:51 AM
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in article ,
Paul_Morphy at wrote on 5/3/04 11:29 PM:
"Uwe" wrote in message
...
So now is the time to start the construction of that more advanced version
of a starter transmitter using two 807 as finals, who was mentioning that
design way back??
You almost have to put those 807s in push-pull, for aesthetic reasons. That
is easier to do with plug-in coils than with a bandswitch. Then you need a
dual variable to tune the dual coils. Swinging link to adjust coupling to
the antenna. This stuff shows up at hamfests sometimes. You may find
someone's old homebrew rig for sale and you can salvage the parts from it.
The Handbooks Tim mentioned will have all the info you need. I started out
with a 1953 Handbook but I can't remember what projects were in it anymore.
They're all over eBay, don't pay too much. Tim's also right about the 1625
tubes. They're the same as 807s except for the filament voltage and socket.
My second transmitter (the first was a single 6V6) used an 807W, a compact
version of the full-size bottle, as the PA. I used a Calumet baking soda can
for a shield.
While you're cruising the hamfests, look for an RCA Transmitting Tube
manual, a small paperback. They're fun to read and there's some application
info in them, as well as the usual datasheets.
I used to use a mercury-wetted relay to key my tube rigs. They're really
fast and make a nice ticking sound when you're keying. They also isolate you
from the keyed voltage and allow the use of most modern keyers. Definitely
in keeping with the period, too. They look like octal vacuum tubes with
metal bulbs but they're shiny, not black. 24 VDC is a common coil voltage.
Do you hang out on the boatanchors group? You might be able to turn up some
parts and lots of info over there.
(Note that I have quit trying to convert you to solid-state! You are
obviously a lost cause. : Have fun.)
73,
"PM"
Paul, I may be a lost cause but I did, after we talked about it, buy the
Experiments in RF design book-great stuff and I also continue to work on my
stamps based controllers even though I can't find a single tube in there...
Thanks for your help
Uwe
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