The circuit you describe should be delivering approximately the peak
voltage, not RMS, so the formula is more like V X V / 100. At 7 volts
peak, that means you're putting out around 1/2 watt. That's a lot below
the 3 watt figure you mentioned, so you should track down why it's so
much lower. Pay special care to the circuit components in the final
transistor output (collector) circuit, and make sure the inductors are
built as described and the components are connected correctly.

Roy Lewallen, W7EL

John Sandin wrote:
. . .
Voltage is measured across my 50 ohm dummy load and rectified using a
.05 mfd ceramic disc cap and a 1N34A diode. Then I'm calculating
thusly:

Power = (Voltage x Voltage) / 50

I'm taking the author's word that this works for a ballpark estimate.
I'm measuring 7 volts across the load, maximum, which works out to 1
watt or less. I've verified that my meter is accurate.
. . .

On Sun, 05 Oct 2003 13:27:59 GMT, "W3JDR" wrote:

John,
Can you post a picture of your unit somewhere(top and bottom views) so we
can see what the PCB & wiring layout looks like?


I want to thank everyone. I never dreamed that I'd get so many great
responses, within a few hours of my original post.

I have put up a website with a link to the web page that inspired me
to do this. Below that are a bunch of pics of my project. Any
comments and advice are welcome.

I guess it would have been easier and even cheaper to buy a kit. But
I had fun building this, and I guess I'll have almost as much fun
rebuilding it.


-John Sandin KC0QWE

Remove the "T" to respond by e-mail

On Sun, 05 Oct 2003 13:27:59 GMT, "W3JDR" wrote:

John,
Can you post a picture of your unit somewhere(top and bottom views) so we
can see what the PCB & wiring layout looks like?


I want to thank everyone. I never dreamed that I'd get so many great
responses, within a few hours of my original post.

I have put up a website with a link to the web page that inspired me
to do this. Below that are a bunch of pics of my project. Any
comments and advice are welcome.

I guess it would have been easier and even cheaper to buy a kit. But
I had fun building this, and I guess I'll have almost as much fun
rebuilding it.


-John Sandin KC0QWE

Remove the "T" to respond by e-mail

Here's the link to my project website..

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


On Mon, 06 Oct 2003 02:56:38 GMT,
(John Sandin) wrote:


On Sun, 05 Oct 2003 13:27:59 GMT, "W3JDR" wrote:

John,
Can you post a picture of your unit somewhere(top and bottom views) so we
can see what the PCB & wiring layout looks like?


I want to thank everyone. I never dreamed that I'd get so many great
responses, within a few hours of my original post.

I have put up a website with a link to the web page that inspired me
to do this. Below that are a bunch of pics of my project. Any
comments and advice are welcome.

I guess it would have been easier and even cheaper to buy a kit. But
I had fun building this, and I guess I'll have almost as much fun
rebuilding it.


-John Sandin KC0QWE

Remove the "T" to respond by e-mail



-John Sandin KC0QWE

Remove the "T" to respond by e-mail

Here's the link to my project website..

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


On Mon, 06 Oct 2003 02:56:38 GMT,
(John Sandin) wrote:


On Sun, 05 Oct 2003 13:27:59 GMT, "W3JDR" wrote:

John,
Can you post a picture of your unit somewhere(top and bottom views) so we
can see what the PCB & wiring layout looks like?


I want to thank everyone. I never dreamed that I'd get so many great
responses, within a few hours of my original post.

I have put up a website with a link to the web page that inspired me
to do this. Below that are a bunch of pics of my project. Any
comments and advice are welcome.

I guess it would have been easier and even cheaper to buy a kit. But
I had fun building this, and I guess I'll have almost as much fun
rebuilding it.


-John Sandin KC0QWE

Remove the "T" to respond by e-mail



-John Sandin KC0QWE

Remove the "T" to respond by e-mail

John,
I had a look. The outside cosmetics are very nice, but the internal wiring
is kind of scary for RF. I suspect you have a lot of coupling between the
wires that are bundled together. In a more ideal setup, the PCB would have
been mounted directly on or very near to the two coils and tuning caps.

Here are my suggestions for troublehooting. Do them one at a time and see if
any of them make a major difference:
1) Remove the lowpass filter and mearure the RF output again . Maybe the
filter cutoff frequency is wrong.
2) Unbundle the wires and spread them apart. Does that improve anything?
3) Remove any interconnect wiring that isn't absolutely essential for RF
operation. Strap the switch lines to their proper state on the PCB & remove
lamp wiring. See if that improves things.
4) Measure the overall DC current and the DC current into the amplifier
stage only. When the amplifier is driven properly, getting 3 watts RF out
will require about 4-5 watts of DC into the final (Vfinal x Ifinal). If the
current is much too low, check out whether the oscillator stage is driving
it properly. If it's too high for the RF you're seeing, check the final
stage tuning and possibility of an oscillation.

Good Luck,
Joe
W3JDR


"John Sandin" wrote in message
...
Here's the link to my project website..

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


On Mon, 06 Oct 2003 02:56:38 GMT,
(John Sandin) wrote:


On Sun, 05 Oct 2003 13:27:59 GMT, "W3JDR" wrote:

John,
Can you post a picture of your unit somewhere(top and bottom views) so
we
can see what the PCB & wiring layout looks like?


I want to thank everyone. I never dreamed that I'd get so many great
responses, within a few hours of my original post.

I have put up a website with a link to the web page that inspired me
to do this. Below that are a bunch of pics of my project. Any
comments and advice are welcome.

I guess it would have been easier and even cheaper to buy a kit. But
I had fun building this, and I guess I'll have almost as much fun
rebuilding it.


-John Sandin KC0QWE

Remove the "T" to respond by e-mail



-John Sandin KC0QWE

Remove the "T" to respond by e-mail

John,
I had a look. The outside cosmetics are very nice, but the internal wiring
is kind of scary for RF. I suspect you have a lot of coupling between the
wires that are bundled together. In a more ideal setup, the PCB would have
been mounted directly on or very near to the two coils and tuning caps.

Here are my suggestions for troublehooting. Do them one at a time and see if
any of them make a major difference:
1) Remove the lowpass filter and mearure the RF output again . Maybe the
filter cutoff frequency is wrong.
2) Unbundle the wires and spread them apart. Does that improve anything?
3) Remove any interconnect wiring that isn't absolutely essential for RF
operation. Strap the switch lines to their proper state on the PCB & remove
lamp wiring. See if that improves things.
4) Measure the overall DC current and the DC current into the amplifier
stage only. When the amplifier is driven properly, getting 3 watts RF out
will require about 4-5 watts of DC into the final (Vfinal x Ifinal). If the
current is much too low, check out whether the oscillator stage is driving
it properly. If it's too high for the RF you're seeing, check the final
stage tuning and possibility of an oscillation.

Good Luck,
Joe
W3JDR


"John Sandin" wrote in message
...
Here's the link to my project website..

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


On Mon, 06 Oct 2003 02:56:38 GMT,
(John Sandin) wrote:


On Sun, 05 Oct 2003 13:27:59 GMT, "W3JDR" wrote:

John,
Can you post a picture of your unit somewhere(top and bottom views) so
we
can see what the PCB & wiring layout looks like?


I want to thank everyone. I never dreamed that I'd get so many great
responses, within a few hours of my original post.

I have put up a website with a link to the web page that inspired me
to do this. Below that are a bunch of pics of my project. Any
comments and advice are welcome.

I guess it would have been easier and even cheaper to buy a kit. But
I had fun building this, and I guess I'll have almost as much fun
rebuilding it.


-John Sandin KC0QWE

Remove the "T" to respond by e-mail



-John Sandin KC0QWE

Remove the "T" to respond by e-mail

"John Sandin" wrote in message
...

I guess it would have been easier and even cheaper to buy a kit. But
I had fun building this, and I guess I'll have almost as much fun
rebuilding it.

One of the wonderful things about amateur radio is that there are so many
facets to explore. Each of us finds his own favorites, but in my mind,
there are few things in life as fun as building and operating your own
equipment.

Your low pass filter leaps out at me. Typically, the coil windings are
spread out over 80% of the toroid, rather than 20%. If, in fact, this was
the intent of the low pass filter design, then your inductances could be
quite a way off. Not only would this change the cutoff frequency of your
LPF (raising it most probably, so not likely the direct cause of low
output), but it would also change the impedance the transmitter sees. (I'm
leaping to the conclusion here that the LPF is between the transmitter and
the antenna). What this means is that the transmitter isn't seeing 50 ohms
even if your antenna is resonant. This would result in the final heating,
and could also favor the parasitics that I suspect we have going on here.

As you explore what's going on here, keep in mind that these things aren't
magic, what they do is always goverened by the laws of physics. Validate by
measurement that what you think is happening is, in fact, what is going on.
You really don't need a ton of test equipment. Granted, lacking lots of
gear, each measurement can be a bit of a project in itself, but once you
have a DMM and have built an RF probe (about a buck's worth of parts), you
can make pretty much any measurement if you think it through.

...

"John Sandin" wrote in message
...

I guess it would have been easier and even cheaper to buy a kit. But
I had fun building this, and I guess I'll have almost as much fun
rebuilding it.

One of the wonderful things about amateur radio is that there are so many
facets to explore. Each of us finds his own favorites, but in my mind,
there are few things in life as fun as building and operating your own
equipment.

Your low pass filter leaps out at me. Typically, the coil windings are
spread out over 80% of the toroid, rather than 20%. If, in fact, this was
the intent of the low pass filter design, then your inductances could be
quite a way off. Not only would this change the cutoff frequency of your
LPF (raising it most probably, so not likely the direct cause of low
output), but it would also change the impedance the transmitter sees. (I'm
leaping to the conclusion here that the LPF is between the transmitter and
the antenna). What this means is that the transmitter isn't seeing 50 ohms
even if your antenna is resonant. This would result in the final heating,
and could also favor the parasitics that I suspect we have going on here.

As you explore what's going on here, keep in mind that these things aren't
magic, what they do is always goverened by the laws of physics. Validate by
measurement that what you think is happening is, in fact, what is going on.
You really don't need a ton of test equipment. Granted, lacking lots of
gear, each measurement can be a bit of a project in itself, but once you
have a DMM and have built an RF probe (about a buck's worth of parts), you
can make pretty much any measurement if you think it through.

...

John Sandin wrote:

Here's the link to my project website..

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


Your heatsink (at least, I think it's the heatsink) is
inefficient (finless), and you mentioned using lots of
heat sink grease. You *can* have too much grease.
Putting in a bigger sink with fins and a small amount
of heatsink compound won't fix your problem - but it may
be a good idea, once you have fixed it.

The fact that the xsistor is heating up at least means that
the rig is "making power". If we assume that the power
it's making is RF at the right frequency, then suspect the
output circuit from the collector outwards up to and
including the antenna. And, with your antenna at 7 feet,
and fed by a questionable mix of coax, it may be the source
of the trouble.

Try feeding the rig into a good 50 ohm dummy load and see if
that allows the transistor to run cooler.