The link below shows my attempt to build a 3-watt transmitter for 40
meters or 80 meters, based on an article in QST, June 1967 and an
adaptation thereof by KC6WDK.

http://www.kcnet.com/~oyster/transmi...ansmitter.html

I've had some success since I posted last, but I want to get the
output clean before I go on the air with it. I've had very little
spare time, but I've managed to improve the performance quite a bit,
through a lot of frustrating trial and error.

The good news: The transistor does not become egg-frying hot anymore.
Now it's just barely warm. I began trying the suggestions about
grounding and parts placement provided to me by the good people at
rec.radio.amateur.homebrew and qrp-l. What seemed to help the most
were the grounding suggestions; I moved several components' chassis
connections to within an inch of Q2's emitter, and that seemed to help
to increase the output and decrease the self-oscillation, which can
now be eliminated via the variable caps for the oscillator and
amplifier stages (C1 and C2). I also realized how close the crystal
was to Q2 in my original assembly, so I moved the crystal over near
the oscillator section, and that seemed to help, also. The chirp is
still a little bothersome, but the transmitter appears to be putting
out around 2 watts into a dummy load, sans lowpass filter.

I got good results by isolating C2 from the chassis, and grounding it
via a separate wire to the point where Q2's emitter is grounded.

I'm having quite a time trying to get rid of harmonics, which I'm
"measuring" using my Icom R71A receiver, which is across the room from
the transmitter now. Slowly but surely I am making small
modifications resulting in small improvements. I'm rebuilding the
coils now. More details and new pictures of the rebuilt transmitter
are on the website. Thanks to all who offered advice, and any further
advice is more than welcome.


-John Sandin KC0QWE

Remove the "T" to respond by e-mail

John

Congratulations. It's great to see your progress and thank you for sharing.

Chirp is a fairly common problem, and it almost always has to do with the
voltage on the oscillator.

Even though QRP rigs don't draw much current, the inrush on key down can
cause the voltage to drop quickly. The first thing to do is to beef up the
wires from the power supply to the rig, and keep them short if possible.
You might only be drawing an amp on key down, but #12 wire from the power
supply isn't overkill, even larger if your run is more than a couple feet.
Keep the power wires as fat as possible right up to the oscillator. If you
are using batteries and they are getting a little stale, the internal
resistance of the batteries could be working against you, as well. Fat wire
is pretty reasonable at home supply stores like Lowe's or Home Depot, but
generally you want stranded wire as it's a lot more manageable in the larger
sizes, tho the solid wire is easier to get.

If that's not adequate, the next move is to regulate the voltage to the
oscillator. Some rigs even go to the extreme of adding double regulation to
the oscillator. The messy bit is that three terminal requlators need at
least a couple of volts extra to do their work. Your supply appears to be
28 volts, so if you were to go with 2 regulators (maybe overkill) then you
would need to fiddle with yout oscillator to get it to work at around 20 or
22 volts, instead of 28. Actually, you might consider dropping the
oscillator supply below that. After voltage drop, the next most common
cause of chirp is heating of the oecillator components, so reducing the
energy in that part of the circuit is a good thing. Recognize, though, that
changing that voltage means you would need to recalculate the transformer at
L1/L2 to account for the new output impedance.

Rich harmonics generally occur as a result of driving the amplifier too
hard, although your output pi network could be off, as well. Before getting
too carried away, however, keep in mind that even with a clean transmitter,
you will hear some harmonics on a radio in the same room. You would like
the harmonics to be down at least 40 or 50 db, so if you can transmit into a
dummy load and get your receiver far enough away that the fundamental is on
scale of the S meter, then you can assess whether the harmonics are in the
right neighborhood.

...

"John Sandin" wrote in message
...
The link below shows my attempt to build a 3-watt transmitter for 40
meters or 80 meters, based on an article in QST, June 1967 and an
adaptation thereof by KC6WDK.

http://www.kcnet.com/~oyster/transmi...ansmitter.html

I've had some success since I posted last, but I want to get the
output clean before I go on the air with it. I've had very little
spare time, but I've managed to improve the performance quite a bit,
through a lot of frustrating trial and error.

The good news: The transistor does not become egg-frying hot anymore.
Now it's just barely warm. I began trying the suggestions about
grounding and parts placement provided to me by the good people at
rec.radio.amateur.homebrew and qrp-l. What seemed to help the most
were the grounding suggestions; I moved several components' chassis
connections to within an inch of Q2's emitter, and that seemed to help
to increase the output and decrease the self-oscillation, which can
now be eliminated via the variable caps for the oscillator and
amplifier stages (C1 and C2). I also realized how close the crystal
was to Q2 in my original assembly, so I moved the crystal over near
the oscillator section, and that seemed to help, also. The chirp is
still a little bothersome, but the transmitter appears to be putting
out around 2 watts into a dummy load, sans lowpass filter.

I got good results by isolating C2 from the chassis, and grounding it
via a separate wire to the point where Q2's emitter is grounded.

I'm having quite a time trying to get rid of harmonics, which I'm
"measuring" using my Icom R71A receiver, which is across the room from
the transmitter now. Slowly but surely I am making small
modifications resulting in small improvements. I'm rebuilding the
coils now. More details and new pictures of the rebuilt transmitter
are on the website. Thanks to all who offered advice, and any further
advice is more than welcome.


-John Sandin KC0QWE

Remove the "T" to respond by e-mail

John

Congratulations. It's great to see your progress and thank you for sharing.

Chirp is a fairly common problem, and it almost always has to do with the
voltage on the oscillator.

Even though QRP rigs don't draw much current, the inrush on key down can
cause the voltage to drop quickly. The first thing to do is to beef up the
wires from the power supply to the rig, and keep them short if possible.
You might only be drawing an amp on key down, but #12 wire from the power
supply isn't overkill, even larger if your run is more than a couple feet.
Keep the power wires as fat as possible right up to the oscillator. If you
are using batteries and they are getting a little stale, the internal
resistance of the batteries could be working against you, as well. Fat wire
is pretty reasonable at home supply stores like Lowe's or Home Depot, but
generally you want stranded wire as it's a lot more manageable in the larger
sizes, tho the solid wire is easier to get.

If that's not adequate, the next move is to regulate the voltage to the
oscillator. Some rigs even go to the extreme of adding double regulation to
the oscillator. The messy bit is that three terminal requlators need at
least a couple of volts extra to do their work. Your supply appears to be
28 volts, so if you were to go with 2 regulators (maybe overkill) then you
would need to fiddle with yout oscillator to get it to work at around 20 or
22 volts, instead of 28. Actually, you might consider dropping the
oscillator supply below that. After voltage drop, the next most common
cause of chirp is heating of the oecillator components, so reducing the
energy in that part of the circuit is a good thing. Recognize, though, that
changing that voltage means you would need to recalculate the transformer at
L1/L2 to account for the new output impedance.

Rich harmonics generally occur as a result of driving the amplifier too
hard, although your output pi network could be off, as well. Before getting
too carried away, however, keep in mind that even with a clean transmitter,
you will hear some harmonics on a radio in the same room. You would like
the harmonics to be down at least 40 or 50 db, so if you can transmit into a
dummy load and get your receiver far enough away that the fundamental is on
scale of the S meter, then you can assess whether the harmonics are in the
right neighborhood.

...

"John Sandin" wrote in message
...
The link below shows my attempt to build a 3-watt transmitter for 40
meters or 80 meters, based on an article in QST, June 1967 and an
adaptation thereof by KC6WDK.

http://www.kcnet.com/~oyster/transmi...ansmitter.html

I've had some success since I posted last, but I want to get the
output clean before I go on the air with it. I've had very little
spare time, but I've managed to improve the performance quite a bit,
through a lot of frustrating trial and error.

The good news: The transistor does not become egg-frying hot anymore.
Now it's just barely warm. I began trying the suggestions about
grounding and parts placement provided to me by the good people at
rec.radio.amateur.homebrew and qrp-l. What seemed to help the most
were the grounding suggestions; I moved several components' chassis
connections to within an inch of Q2's emitter, and that seemed to help
to increase the output and decrease the self-oscillation, which can
now be eliminated via the variable caps for the oscillator and
amplifier stages (C1 and C2). I also realized how close the crystal
was to Q2 in my original assembly, so I moved the crystal over near
the oscillator section, and that seemed to help, also. The chirp is
still a little bothersome, but the transmitter appears to be putting
out around 2 watts into a dummy load, sans lowpass filter.

I got good results by isolating C2 from the chassis, and grounding it
via a separate wire to the point where Q2's emitter is grounded.

I'm having quite a time trying to get rid of harmonics, which I'm
"measuring" using my Icom R71A receiver, which is across the room from
the transmitter now. Slowly but surely I am making small
modifications resulting in small improvements. I'm rebuilding the
coils now. More details and new pictures of the rebuilt transmitter
are on the website. Thanks to all who offered advice, and any further
advice is more than welcome.


-John Sandin KC0QWE

Remove the "T" to respond by e-mail

You are cool, John. I checked your site.

It of course makes you appreciate the engineering which goes into a modern
radio. It also gives you a sense of accomplishment when you make it work --
and you will.

I used to do a lot of playing around with the stuff -- not because I enjoyed
it then -- just because I was trying to make junk work. Not it seems like
it would be fun again.

Good luck.
Phil KD0UN
"John Sandin" wrote in message
...
The link below shows my attempt to build a 3-watt transmitter for 40
meters or 80 meters, based on an article in QST, June 1967 and an
adaptation thereof by KC6WDK.

http://www.kcnet.com/~oyster/transmi...ansmitter.html

I've had some success since I posted last, but I want to get the
output clean before I go on the air with it. I've had very little
spare time, but I've managed to improve the performance quite a bit,
through a lot of frustrating trial and error.

The good news: The transistor does not become egg-frying hot anymore.
Now it's just barely warm. I began trying the suggestions about
grounding and parts placement provided to me by the good people at
rec.radio.amateur.homebrew and qrp-l. What seemed to help the most
were the grounding suggestions; I moved several components' chassis
connections to within an inch of Q2's emitter, and that seemed to help
to increase the output and decrease the self-oscillation, which can
now be eliminated via the variable caps for the oscillator and
amplifier stages (C1 and C2). I also realized how close the crystal
was to Q2 in my original assembly, so I moved the crystal over near
the oscillator section, and that seemed to help, also. The chirp is
still a little bothersome, but the transmitter appears to be putting
out around 2 watts into a dummy load, sans lowpass filter.

I got good results by isolating C2 from the chassis, and grounding it
via a separate wire to the point where Q2's emitter is grounded.

I'm having quite a time trying to get rid of harmonics, which I'm
"measuring" using my Icom R71A receiver, which is across the room from
the transmitter now. Slowly but surely I am making small
modifications resulting in small improvements. I'm rebuilding the
coils now. More details and new pictures of the rebuilt transmitter
are on the website. Thanks to all who offered advice, and any further
advice is more than welcome.


-John Sandin KC0QWE

Remove the "T" to respond by e-mail

You are cool, John. I checked your site.

It of course makes you appreciate the engineering which goes into a modern
radio. It also gives you a sense of accomplishment when you make it work --
and you will.

I used to do a lot of playing around with the stuff -- not because I enjoyed
it then -- just because I was trying to make junk work. Not it seems like
it would be fun again.

Good luck.
Phil KD0UN
"John Sandin" wrote in message
...
The link below shows my attempt to build a 3-watt transmitter for 40
meters or 80 meters, based on an article in QST, June 1967 and an
adaptation thereof by KC6WDK.

http://www.kcnet.com/~oyster/transmi...ansmitter.html

I've had some success since I posted last, but I want to get the
output clean before I go on the air with it. I've had very little
spare time, but I've managed to improve the performance quite a bit,
through a lot of frustrating trial and error.

The good news: The transistor does not become egg-frying hot anymore.
Now it's just barely warm. I began trying the suggestions about
grounding and parts placement provided to me by the good people at
rec.radio.amateur.homebrew and qrp-l. What seemed to help the most
were the grounding suggestions; I moved several components' chassis
connections to within an inch of Q2's emitter, and that seemed to help
to increase the output and decrease the self-oscillation, which can
now be eliminated via the variable caps for the oscillator and
amplifier stages (C1 and C2). I also realized how close the crystal
was to Q2 in my original assembly, so I moved the crystal over near
the oscillator section, and that seemed to help, also. The chirp is
still a little bothersome, but the transmitter appears to be putting
out around 2 watts into a dummy load, sans lowpass filter.

I got good results by isolating C2 from the chassis, and grounding it
via a separate wire to the point where Q2's emitter is grounded.

I'm having quite a time trying to get rid of harmonics, which I'm
"measuring" using my Icom R71A receiver, which is across the room from
the transmitter now. Slowly but surely I am making small
modifications resulting in small improvements. I'm rebuilding the
coils now. More details and new pictures of the rebuilt transmitter
are on the website. Thanks to all who offered advice, and any further
advice is more than welcome.


-John Sandin KC0QWE

Remove the "T" to respond by e-mail

PJ wrote:
You are cool, John. I checked your site.

It of course makes you appreciate the engineering which goes into a modern
radio. It also gives you a sense of accomplishment when you make it work --
and you will.

I used to do a lot of playing around with the stuff -- not because I enjoyed
it then -- just because I was trying to make junk work. Not it seems like
it would be fun again.

Good luck.
Phil KD0UN
"John Sandin" wrote in message
...

The link below shows my attempt to build a 3-watt transmitter for 40
meters or 80 meters, based on an article in QST, June 1967 and an
adaptation thereof by KC6WDK.

http://www.kcnet.com/~oyster/transmi...ansmitter.html

I've had some success since I posted last, but I want to get the
output clean before I go on the air with it. I've had very little
spare time, but I've managed to improve the performance quite a bit,
through a lot of frustrating trial and error.

The good news: The transistor does not become egg-frying hot anymore.
Now it's just barely warm. I began trying the suggestions about
grounding and parts placement provided to me by the good people at
rec.radio.amateur.homebrew and qrp-l. What seemed to help the most
were the grounding suggestions; I moved several components' chassis
connections to within an inch of Q2's emitter, and that seemed to help
to increase the output and decrease the self-oscillation, which can
now be eliminated via the variable caps for the oscillator and
amplifier stages (C1 and C2). I also realized how close the crystal
was to Q2 in my original assembly, so I moved the crystal over near
the oscillator section, and that seemed to help, also. The chirp is
still a little bothersome, but the transmitter appears to be putting
out around 2 watts into a dummy load, sans lowpass filter.

I got good results by isolating C2 from the chassis, and grounding it
via a separate wire to the point where Q2's emitter is grounded.

I'm having quite a time trying to get rid of harmonics, which I'm
"measuring" using my Icom R71A receiver, which is across the room from
the transmitter now. Slowly but surely I am making small
modifications resulting in small improvements. I'm rebuilding the
coils now. More details and new pictures of the rebuilt transmitter
are on the website. Thanks to all who offered advice, and any further
advice is more than welcome.


-John Sandin KC0QWE

Remove the "T" to respond by e-mail





I don't know what the gain of the final is but I wonder if shielding
one of the two plug in coils (since they are not at right angles to each
other) would be a good idea..

PJ wrote:
You are cool, John. I checked your site.

It of course makes you appreciate the engineering which goes into a modern
radio. It also gives you a sense of accomplishment when you make it work --
and you will.

I used to do a lot of playing around with the stuff -- not because I enjoyed
it then -- just because I was trying to make junk work. Not it seems like
it would be fun again.

Good luck.
Phil KD0UN
"John Sandin" wrote in message
...

The link below shows my attempt to build a 3-watt transmitter for 40
meters or 80 meters, based on an article in QST, June 1967 and an
adaptation thereof by KC6WDK.

http://www.kcnet.com/~oyster/transmi...ansmitter.html

I've had some success since I posted last, but I want to get the
output clean before I go on the air with it. I've had very little
spare time, but I've managed to improve the performance quite a bit,
through a lot of frustrating trial and error.

The good news: The transistor does not become egg-frying hot anymore.
Now it's just barely warm. I began trying the suggestions about
grounding and parts placement provided to me by the good people at
rec.radio.amateur.homebrew and qrp-l. What seemed to help the most
were the grounding suggestions; I moved several components' chassis
connections to within an inch of Q2's emitter, and that seemed to help
to increase the output and decrease the self-oscillation, which can
now be eliminated via the variable caps for the oscillator and
amplifier stages (C1 and C2). I also realized how close the crystal
was to Q2 in my original assembly, so I moved the crystal over near
the oscillator section, and that seemed to help, also. The chirp is
still a little bothersome, but the transmitter appears to be putting
out around 2 watts into a dummy load, sans lowpass filter.

I got good results by isolating C2 from the chassis, and grounding it
via a separate wire to the point where Q2's emitter is grounded.

I'm having quite a time trying to get rid of harmonics, which I'm
"measuring" using my Icom R71A receiver, which is across the room from
the transmitter now. Slowly but surely I am making small
modifications resulting in small improvements. I'm rebuilding the
coils now. More details and new pictures of the rebuilt transmitter
are on the website. Thanks to all who offered advice, and any further
advice is more than welcome.


-John Sandin KC0QWE

Remove the "T" to respond by e-mail





I don't know what the gain of the final is but I wonder if shielding
one of the two plug in coils (since they are not at right angles to each
other) would be a good idea..