The ARC-5 transmitter is one of the great piece of electronics out of WWII.
As a kid, my first transmitter was an ARC-5 bought from JJ Glass of Los
Angeles for about $5.95. It was brand new and a beauty to behold. Getting
it working right will teach you everything that you need to know about
electronics (well as of 1957 anyway).

I was able to get mine to key nicely with no chirp at all. I still have a
wall full of them, they are nice to look at. You should be able to find a
schematic on the internet. I found that adjusting the oscillator plate
voltage to the individual transmitter could help solve a lot of problems and
regulated dc on the filaments does wonders, too. They will run 100 watts
without too much strain, although the power supplyis often twice the size of
the transmitter. But, they also run qrp on a much smaller supply and lower
voltage.

Have fun, Colin K7FM


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Thanks to everyone for the encouragement. Next step is to make the conversion
to this little power supply, then tweak that oscillator plate voltage etc. and
see if I can get it on the air. I have already decided not to worry about
keeping this thing "original", eg. will be putting in a new power plug, key
jack, and coax connector etc. I am sure I will have many more questions as I
proceed and will keep you posted with the progress and inevitable mysteries
that will need solving....

Why do you think the regulated dc on the filaments makes such a difference?
Closer to the original battery powered situation? Would that be true for any
old tube transmitter? Or because these particularly were originally designed to
run on 28 volt DC.


Bill, K6TAJ


COLIN LAMB wrote:

The ARC-5 transmitter is one of the great piece of electronics out of WWII.
As a kid, my first transmitter was an ARC-5 bought from JJ Glass of Los
Angeles for about $5.95. It was brand new and a beauty to behold. Getting
it working right will teach you everything that you need to know about
electronics (well as of 1957 anyway).

I was able to get mine to key nicely with no chirp at all. I still have a
wall full of them, they are nice to look at. You should be able to find a
schematic on the internet. I found that adjusting the oscillator plate
voltage to the individual transmitter could help solve a lot of problems and
regulated dc on the filaments does wonders, too. They will run 100 watts
without too much strain, although the power supplyis often twice the size of
the transmitter. But, they also run qrp on a much smaller supply and lower
voltage.

Have fun, Colin K7FM

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Thanks to everyone for the encouragement. Next step is to make the conversion
to this little power supply, then tweak that oscillator plate voltage etc. and
see if I can get it on the air. I have already decided not to worry about
keeping this thing "original", eg. will be putting in a new power plug, key
jack, and coax connector etc. I am sure I will have many more questions as I
proceed and will keep you posted with the progress and inevitable mysteries
that will need solving....

Why do you think the regulated dc on the filaments makes such a difference?
Closer to the original battery powered situation? Would that be true for any
old tube transmitter? Or because these particularly were originally designed to
run on 28 volt DC.


Bill, K6TAJ


COLIN LAMB wrote:

The ARC-5 transmitter is one of the great piece of electronics out of WWII.
As a kid, my first transmitter was an ARC-5 bought from JJ Glass of Los
Angeles for about $5.95. It was brand new and a beauty to behold. Getting
it working right will teach you everything that you need to know about
electronics (well as of 1957 anyway).

I was able to get mine to key nicely with no chirp at all. I still have a
wall full of them, they are nice to look at. You should be able to find a
schematic on the internet. I found that adjusting the oscillator plate
voltage to the individual transmitter could help solve a lot of problems and
regulated dc on the filaments does wonders, too. They will run 100 watts
without too much strain, although the power supplyis often twice the size of
the transmitter. But, they also run qrp on a much smaller supply and lower
voltage.

Have fun, Colin K7FM

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why would you not need to use the Xtal to calibrate the VFO for ham use?

Bill K6TAJ

wrote:

Bill, There is also a tuning eye tube in back of xmtr , the Xtal and
tuning eye is used to calibrate the VFO .You won`t need the Xtal or eye
tube for ham use.. I used an Arc 5 about 60 years ago on 40 mtrs. I had
pretty good output BUT it chirped like all crazy..there were several
schemes to get the chirp out, none of them worked very well..If you can
get the VFO to key without chirping it will be all OK. Good luck 73
Harold W4PQW

why would you not need to use the Xtal to calibrate the VFO for ham use?

Bill K6TAJ

wrote:

Bill, There is also a tuning eye tube in back of xmtr , the Xtal and
tuning eye is used to calibrate the VFO .You won`t need the Xtal or eye
tube for ham use.. I used an Arc 5 about 60 years ago on 40 mtrs. I had
pretty good output BUT it chirped like all crazy..there were several
schemes to get the chirp out, none of them worked very well..If you can
get the VFO to key without chirping it will be all OK. Good luck 73
Harold W4PQW

zeno wrote:

why would you not need to use the Xtal to calibrate the VFO for ham use?

Bill K6TAJ

On the 6-9MHz one I had many moons ago the xtal cal point was up at the
top end, close to 9 MHz and didn't serve much of a purpose for exact 7
MHz calibration. Of course I was *supposed* to be using xtals as a
Novice :-)

It would be preferable just to accurately set the dial at 7MHz. Once
its set its very accurate. Its will be as exact as you can interpolate
across the little swath of the 40 CW band.

-Bill

zeno wrote:

why would you not need to use the Xtal to calibrate the VFO for ham use?

Bill K6TAJ

On the 6-9MHz one I had many moons ago the xtal cal point was up at the
top end, close to 9 MHz and didn't serve much of a purpose for exact 7
MHz calibration. Of course I was *supposed* to be using xtals as a
Novice :-)

It would be preferable just to accurately set the dial at 7MHz. Once
its set its very accurate. Its will be as exact as you can interpolate
across the little swath of the 40 CW band.

-Bill

Question: "Why do you think the regulated dc on the filaments makes such a
difference? Closer to the original battery powered situation? Would that be
true for any
old tube transmitter? Or because these particularly were originally designed
to run on 28 volt DC."

The oscillator obtains feedback by tapping the cathode up on the coil. This
allows the ac on the filaments to modulate the oscillator slightly. A
filament winding was added to reduce this effect, but it does not. Some
ARC-5s have hum modulation - especially when multiplying to 10 meters.

Also, a change in filament voltage causes drift of the vfo. When we were
converting these rigs 50 years ago, it was difficult to get 24 volts
regulated. Today it is a snap. It may be easier to get a regulated 13.8
volts (or 12 volts or anything in between).

In my early hamshack, the test for stability was to switch on the heater and
listen for drift about 30 seconds later. Even the heralded SX-101 would
drift mightily on 10 meters when I did that trick - until I regulated the
filament voltage on the oscillator using the separate transformer that
always kept the heater on.

73, Colin K7FM










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Question: "Why do you think the regulated dc on the filaments makes such a
difference? Closer to the original battery powered situation? Would that be
true for any
old tube transmitter? Or because these particularly were originally designed
to run on 28 volt DC."

The oscillator obtains feedback by tapping the cathode up on the coil. This
allows the ac on the filaments to modulate the oscillator slightly. A
filament winding was added to reduce this effect, but it does not. Some
ARC-5s have hum modulation - especially when multiplying to 10 meters.

Also, a change in filament voltage causes drift of the vfo. When we were
converting these rigs 50 years ago, it was difficult to get 24 volts
regulated. Today it is a snap. It may be easier to get a regulated 13.8
volts (or 12 volts or anything in between).

In my early hamshack, the test for stability was to switch on the heater and
listen for drift about 30 seconds later. Even the heralded SX-101 would
drift mightily on 10 meters when I did that trick - until I regulated the
filament voltage on the oscillator using the separate transformer that
always kept the heater on.

73, Colin K7FM










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Nostalgia. When drafted into the Navy is 1943
my first job was setting up ARC-5 transmitters
and receivers in 336 SNJ (AT-6) aircraft. (among
other things) Later after the war when there wasn't
much money around, I would rewind ARC-5 receivers
and use them for ten-meter converters. In those days
tapping on the case of just about any transmitter or
receiver would produce some modulation. Except for
Collins equipment. The ARC-5 VHF transmitters were
truly awe inspiring when they arrived. 73s W6BWY