On Sun, 05 Oct 2003 04:42:11 GMT,
(John Sandin) wrote:

I am a new technician with code privileges. I built the following CW
transmitter for 40 meters:

http://cs.okanagan.bc.ca/ve7ouc/eng/...nsmitter2.html

It's a solid state 3-watter, based on an article in QST in June 1967.
I used a printed circuit board instead of wiring everything together
directly, as the QST article suggests. So, there are many wires
running from various parts mounted on the chassis to the circuit
board.

I'm getting very little output. After tuning the transmitter, per the
specs, and measuring the output using the method suggested by the
author of the web page, I figure I'm getting 1 watt or less.

How is this figure arrived at? How are you measuring it? 1W doesn't
sound much, but it can go a long way on 40M., given an efficient
antenna system with short, low-loss feeder and matched radiation
resistance.

I am
running this into a dipole cut for 40 meters, which is 7 feet off the
ground.

That's *way* too low! As you must know for any ariel, you gotta get
that thing up as high off the ground as you can and that's even more
important at low frequencies like 7Mhz.

I'm using fundamental frequency HC6/U crystals for 7110 and
7125 kHz. I've been trying for 2 weeks, at all hours of the day and
night, and have had no indication that anyone hears me. I've called
CQ, and I've attempted to answer CQ's. Nothing, after about 100
tries.

I know it's impossible for any of you to know exactly what's wrong,
but I'd like to see what opinions I can glean here.

Is there any reason why I should use FT-243 crystals, as specified in
the article and on the website? I used HC6/U crystals because they
were easy to get.

One of the transistors (Q2) is supposed to be heat sinked. I have put
a large homemeade heat sink on this, using plenty of heat sink grease,
and it gets so hot I can barely touch it.

Something's wrong, then. The heat dissipated in your final transistor
should equate to the output power at the antenna if the system is
matched properly. Sounds like your tranny's trying to dissipate rather
more than a Watt. Are you sure you don't have a feeder/matching
problem somewhere? Have you cut the ariel to the right length? Are you
using a balun? Have you tried a substitute balun?

Also, the transmitter chirps a bit at the beginning of each
transmission, but settles down after a few strokes of the key.

Many thanks for any help you can give.

Get another ham a couple of miles away from you to give you a signal
report. It might show up something useful.
--

"Windows [n.], A thirty-two bit extension and GUI shell to a sixteen bit patch
to an eight bit operating system originally coded for a four bit
microprocessor and produced by a two bit company."

On Sun, 05 Oct 2003 13:50:43 +0100, Paul Burridge
wrote:

snip

I'm getting very little output. After tuning the transmitter, per the
specs, and measuring the output using the method suggested by the
author of the web page, I figure I'm getting 1 watt or less.

How is this figure arrived at? How are you measuring it? 1W doesn't
sound much, but it can go a long way on 40M., given an efficient
antenna system with short, low-loss feeder and matched radiation
resistance.

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.


I am
running this into a dipole cut for 40 meters, which is 7 feet off the
ground.

That's *way* too low! As you must know for any ariel, you gotta get
that thing up as high off the ground as you can and that's even more
important at low frequencies like 7Mhz.

We have a mess of power lines around the house, so it's hard to find a
spot to even get it 7 feet high in a straight line. I'm thinking
about trying it on the roof, which is about 20 feet high at the
highest point, and mabye angling it in the center.


One of the transistors (Q2) is supposed to be heat sinked. I have put
a large homemeade heat sink on this, using plenty of heat sink grease,
and it gets so hot I can barely touch it.

Something's wrong, then. The heat dissipated in your final transistor
should equate to the output power at the antenna if the system is
matched properly. Sounds like your tranny's trying to dissipate rather
more than a Watt. Are you sure you don't have a feeder/matching
problem somewhere? Have you cut the ariel to the right length? Are you
using a balun? Have you tried a substitute balun?

The length of each element is 32' 11", which I calculated for use at
7110 kHz. There's no balun; I'm using coax, the shield is connected
to one element and the center conductor is connected to the other.
The coax might be 75 ohm. Pretty soon I'll have RG-58 for the entire
run, but right now it's a mix of RG-6/U and RG-59/U.


Get another ham a couple of miles away from you to give you a signal
report. It might show up something useful.

I will do that. Thanks.
--


-John Sandin KC0QWE

Remove the "T" to respond by e-mail

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.
. . .

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 13:50:43 +0100, Paul Burridge
wrote:

snip

I'm getting very little output. After tuning the transmitter, per the
specs, and measuring the output using the method suggested by the
author of the web page, I figure I'm getting 1 watt or less.

How is this figure arrived at? How are you measuring it? 1W doesn't
sound much, but it can go a long way on 40M., given an efficient
antenna system with short, low-loss feeder and matched radiation
resistance.

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.


I am
running this into a dipole cut for 40 meters, which is 7 feet off the
ground.

That's *way* too low! As you must know for any ariel, you gotta get
that thing up as high off the ground as you can and that's even more
important at low frequencies like 7Mhz.

We have a mess of power lines around the house, so it's hard to find a
spot to even get it 7 feet high in a straight line. I'm thinking
about trying it on the roof, which is about 20 feet high at the
highest point, and mabye angling it in the center.


One of the transistors (Q2) is supposed to be heat sinked. I have put
a large homemeade heat sink on this, using plenty of heat sink grease,
and it gets so hot I can barely touch it.

Something's wrong, then. The heat dissipated in your final transistor
should equate to the output power at the antenna if the system is
matched properly. Sounds like your tranny's trying to dissipate rather
more than a Watt. Are you sure you don't have a feeder/matching
problem somewhere? Have you cut the ariel to the right length? Are you
using a balun? Have you tried a substitute balun?

The length of each element is 32' 11", which I calculated for use at
7110 kHz. There's no balun; I'm using coax, the shield is connected
to one element and the center conductor is connected to the other.
The coax might be 75 ohm. Pretty soon I'll have RG-58 for the entire
run, but right now it's a mix of RG-6/U and RG-59/U.


Get another ham a couple of miles away from you to give you a signal
report. It might show up something useful.

I will do that. Thanks.
--


-John Sandin KC0QWE

Remove the "T" to respond by e-mail