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Old December 21st 04, 09:29 PM
zeno
 
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Default 6L6 single tube transmitter

I came across a cute little homebrew CW transmitter utilizing only a
single 6L6. Mostly made from radio and audio junkbox parts, it does
seem to work. I put it on the air briefly with its 40 meter Xtal and
monitored the signal on another antenna. Sounds kind of chirpy,
actually worse than chirpy. Needs some kind of work or upgrade or
correction. I did some web searching but could not actually come up
with a schematic for this rig, probably out of some old magazine or
something. I do not quite understand how it works without a power
supply rectifier. There is nothing under the hood which looks like a
diode or selenium rectifier. Anyone have a clue as to this circuit. I
am kind of new to this. How might I proceed to make this little rig
into a useable QRP unit. I think it probably makes something under 10
watts, and the cw sounds goofy, wimpy, and wobbly. It is someone's old
nice lay out failure, but it would be a fun challenge to convert it
into something useful. Anyone seen a circuit for a singl 6L6 rig?...who
knows maybe it has the wrong tube in there. Hmmmm....how to do the
detective work on this????

I have a certain nostalgia for simple one tube rigs, when I was a
novice in the early 50s as a kid I built this crazy rig with a single
117N7 that worked great with my very compromised end-fed random wire. I
have recently found the schematic for that one, but it seems kind of
crazy to build that one again, but who knows....the schematic for the
117N7 rig can be found on page 38 of "Radio For The Millions", 1945
Popular Science Publishing Co. Inc. This illustration has the chassis
plugged into the AC neutral/gound side. Another variation appears on
page 105 in "Ham Radio Projects" 1968 by Bert Simon, a circuit which
looks even more scarry since you only plug into the hot leg of the AC
outlet, and then ground the chassis to earth ground. I do not know how
I lived to tell you now that it was my first rig!

There is a one-tube rig on page 99 of "Ham Projects..." which uses a
6AV5 but that is not
the circuit I see in this unkown 6L6 rig. Let me know if you know of a
source for this single 6L6 transmitter. Nothing in either of the books
mentioned has one like this.

Other clues: it has three rf (air core) chokes, no other iron core
choke, uses two variable condensers, keys thru one of these chokes to
pin 8. Another choke goes from the antenna center pin to the chassis
ground. The 3 rf chokes used appear to be identical.

Bill / K6TAJ