The transmitter can work without a separate rectifier. I recall a circuit
from the 30's in which the transmitter tube is used also as the rectifier.
I think it was in the RCA handbook. I sort of recall an 813 tube, but that
may have been a bit early for the 813. Even in those days, it was not
"state of the art".

Now, I will have to look for the circuit, but the oscillator tube can also
serve as the rectifier. It complicates things a bit and is not in any of
the Handbooks. Never have seen a 6L6 circuit configured that way, but it
can be done and was done in the 30's in at least one circuit.

Colin K7FM




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I am looking at "Practical Radio Telegraphy" dated 1928. The RCA P-8
transmitter is described with tube converter ET-3628.

This converter is a tube replacement for the "quenched and synchrnous gaps
formerly located on the power panel". it runs 1.5 kw using 2 tubes. One of
the problems mentioned is "fading or swinging signals", in which it is
stated that "such difficulties may be encountered in the case of a heavy sea
causing variation of the antenna capacity by the rolling of the vessel ..."
it is mentioned that if, on occasion, one tube burns out and there is no
replacement, the circuit may be operated as a half wave rectifier with just
one tube. Even more interesting is what to do if both tubes fail and no
spares are available: "the operator may connect his transmitter in
plain-aerial style. This is accomplished by removing all of the connections
from the three secondary terminals of the plate transformer and connecting
the antenna to one outside terminal of this transformer, and the ground to
the other. The safety gap shunted across the secondary terminals will then
function as an oscillatory spark discharger."

DO NOT TRY THIS AT HOME. I PRESUME MORE THAN ONE SAILOR TRIED CLEANING BIRD
POOP OFF THE TRANSMITTING AERIAL AND BECAME WELDED TO THE DECK WITH THIS
SYSTEM.

Using a Poulsen Tikker form of detection, this transmitter may not have
sounded that much different from those that had dc on the plates.

Colin K7FM


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I am looking at "Practical Radio Telegraphy" dated 1928. The RCA P-8
transmitter is described with tube converter ET-3628.

This converter is a tube replacement for the "quenched and synchrnous gaps
formerly located on the power panel". it runs 1.5 kw using 2 tubes. One of
the problems mentioned is "fading or swinging signals", in which it is
stated that "such difficulties may be encountered in the case of a heavy sea
causing variation of the antenna capacity by the rolling of the vessel ..."
it is mentioned that if, on occasion, one tube burns out and there is no
replacement, the circuit may be operated as a half wave rectifier with just
one tube. Even more interesting is what to do if both tubes fail and no
spares are available: "the operator may connect his transmitter in
plain-aerial style. This is accomplished by removing all of the connections
from the three secondary terminals of the plate transformer and connecting
the antenna to one outside terminal of this transformer, and the ground to
the other. The safety gap shunted across the secondary terminals will then
function as an oscillatory spark discharger."

DO NOT TRY THIS AT HOME. I PRESUME MORE THAN ONE SAILOR TRIED CLEANING BIRD
POOP OFF THE TRANSMITTING AERIAL AND BECAME WELDED TO THE DECK WITH THIS
SYSTEM.

Using a Poulsen Tikker form of detection, this transmitter may not have
sounded that much different from those that had dc on the plates.

Colin K7FM


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Colin,
That's really interesting. I was not aware that could be done. However, I
would
think that the chances that the 6L6 circuit was configured to work in that
fashion
are slim at best (but then one never knows).
Thanks for the interesting information.
Roger, KL7Q

COLIN LAMB wrote in message
ink.net...
I am looking at "Practical Radio Telegraphy" dated 1928. The RCA P-8
transmitter is described with tube converter ET-3628.

This converter is a tube replacement for the "quenched and synchrnous gaps
formerly located on the power panel". it runs 1.5 kw using 2 tubes. One
of
the problems mentioned is "fading or swinging signals", in which it is
stated that "such difficulties may be encountered in the case of a heavy
sea
causing variation of the antenna capacity by the rolling of the vessel
...."
it is mentioned that if, on occasion, one tube burns out and there is no
replacement, the circuit may be operated as a half wave rectifier with
just
one tube. Even more interesting is what to do if both tubes fail and no
spares are available: "the operator may connect his transmitter in
plain-aerial style. This is accomplished by removing all of the
connections
from the three secondary terminals of the plate transformer and connecting
the antenna to one outside terminal of this transformer, and the ground to
the other. The safety gap shunted across the secondary terminals will
then
function as an oscillatory spark discharger."

DO NOT TRY THIS AT HOME. I PRESUME MORE THAN ONE SAILOR TRIED CLEANING
BIRD
POOP OFF THE TRANSMITTING AERIAL AND BECAME WELDED TO THE DECK WITH THIS
SYSTEM.

Using a Poulsen Tikker form of detection, this transmitter may not have
sounded that much different from those that had dc on the plates.

Colin K7FM


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Colin,
That's really interesting. I was not aware that could be done. However, I
would
think that the chances that the 6L6 circuit was configured to work in that
fashion
are slim at best (but then one never knows).
Thanks for the interesting information.
Roger, KL7Q

COLIN LAMB wrote in message
ink.net...
I am looking at "Practical Radio Telegraphy" dated 1928. The RCA P-8
transmitter is described with tube converter ET-3628.

This converter is a tube replacement for the "quenched and synchrnous gaps
formerly located on the power panel". it runs 1.5 kw using 2 tubes. One
of
the problems mentioned is "fading or swinging signals", in which it is
stated that "such difficulties may be encountered in the case of a heavy
sea
causing variation of the antenna capacity by the rolling of the vessel
...."
it is mentioned that if, on occasion, one tube burns out and there is no
replacement, the circuit may be operated as a half wave rectifier with
just
one tube. Even more interesting is what to do if both tubes fail and no
spares are available: "the operator may connect his transmitter in
plain-aerial style. This is accomplished by removing all of the
connections
from the three secondary terminals of the plate transformer and connecting
the antenna to one outside terminal of this transformer, and the ground to
the other. The safety gap shunted across the secondary terminals will
then
function as an oscillatory spark discharger."

DO NOT TRY THIS AT HOME. I PRESUME MORE THAN ONE SAILOR TRIED CLEANING
BIRD
POOP OFF THE TRANSMITTING AERIAL AND BECAME WELDED TO THE DECK WITH THIS
SYSTEM.

Using a Poulsen Tikker form of detection, this transmitter may not have
sounded that much different from those that had dc on the plates.

Colin K7FM


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Deep down in my memory banks, I recall seeing an OSS transmitter from WWII
that used a similar circuit to avoid the failure of a rectifier tube, where
the 6L6 was used as a rectifier also. It did make sense, since the
rectifier tube was more fragile than the metal 6L6. Otherwise, it would
make no sense, other than to confuse your buddy - like using a 6L6 for a
rectifier and a 5U4 for the final output stage (sure it can be done).

Colin K7FM


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Deep down in my memory banks, I recall seeing an OSS transmitter from WWII
that used a similar circuit to avoid the failure of a rectifier tube, where
the 6L6 was used as a rectifier also. It did make sense, since the
rectifier tube was more fragile than the metal 6L6. Otherwise, it would
make no sense, other than to confuse your buddy - like using a 6L6 for a
rectifier and a 5U4 for the final output stage (sure it can be done).

Colin K7FM


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On closer examination again, I do now see a couple of small diodes (both have
the number 205) which were hiding behind some black spaghetti pushed up against
them. This little homebrew seems to have been carefully assembled and I have no
reason to believe that the 6L6 is not the correct tube. The little rig does
work, but, as mentioned, the CW note was quite distorted and unacceptable. How
would one go about trouble shooting this problem. At this point I have limited
bench equipment , but might consider acquiring some. An oscilloscope is high on
the want list. Can you point to a part of the circuit which would result in
this very chirpy and wobbly CW tone. I would have to fire it up again to
remember how best to describe the sound of this signal.

Bill K6TAJ



Roger and Ute Brown wrote:

Bill,
It sounds like you've been around awhile and have built some stuff in the
past.
Surely you can look at the circuit and figure out what is powering the
thing. Put your
meter into that thing and start measuring voltages (from the line cord,
through the transformer and on...)
Of course, if you find "any" DC - you've got a diode someplace. Take some
paper and draw out the schematic (can't be to hard for one tube circuit).
That
will show you what you have. Check the tube base wiring against the 6L6 and
see if everything
goes to the correct pins for such a tube. It's possible you should have a
tube which sports a rectifier (diode section) and another tube in the same
envelope). At any rate - a part by part inspection resulting in a schematic
will tell all!
It's rather elementary. I'd be interested to hear what you find.
Good luck,
Roger, KL7Q

zeno wrote in message ...
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

On closer examination again, I do now see a couple of small diodes (both have
the number 205) which were hiding behind some black spaghetti pushed up against
them. This little homebrew seems to have been carefully assembled and I have no
reason to believe that the 6L6 is not the correct tube. The little rig does
work, but, as mentioned, the CW note was quite distorted and unacceptable. How
would one go about trouble shooting this problem. At this point I have limited
bench equipment , but might consider acquiring some. An oscilloscope is high on
the want list. Can you point to a part of the circuit which would result in
this very chirpy and wobbly CW tone. I would have to fire it up again to
remember how best to describe the sound of this signal.

Bill K6TAJ



Roger and Ute Brown wrote:

Bill,
It sounds like you've been around awhile and have built some stuff in the
past.
Surely you can look at the circuit and figure out what is powering the
thing. Put your
meter into that thing and start measuring voltages (from the line cord,
through the transformer and on...)
Of course, if you find "any" DC - you've got a diode someplace. Take some
paper and draw out the schematic (can't be to hard for one tube circuit).
That
will show you what you have. Check the tube base wiring against the 6L6 and
see if everything
goes to the correct pins for such a tube. It's possible you should have a
tube which sports a rectifier (diode section) and another tube in the same
envelope). At any rate - a part by part inspection resulting in a schematic
will tell all!
It's rather elementary. I'd be interested to hear what you find.
Good luck,
Roger, KL7Q

zeno wrote in message ...
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

Chirp can be caused by different causes.

1. The crystal may simply change frequency when first loaded. Try a
different crystal, or try the crystal in a different transmitter.

2. Feedback may be incorrect. Too much feedback can cause chirp.
Depending upon the circuit, you can change feedback by varying the
capacitance between grid and cathode.

3. Voltage stabilization. A stable voltage is less likely to chirp.
Sometimes varying the screen voltage will help make the oscillator less
likely to drift.

Draw your circuit out and match it to one in the older Radio Amateur
Handbook. Oscillator circuits are as simple as the Model T.

Colin K7FM


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