Colt Black Shadow low output

[TM86]

Got a Colt Black Shadow base (1000) here that just doesn't seem to be outputting like it should. I'm getting about 10 watts max on sideband. I've been through the coils in the transmit section, and I can sure drop the power, but not bring it any higher.

The radio has been recapped, but not modified that I can tell. The power supply seems to work, and receive is good.

Open to any suggestions that don't involve selling it or throwing it away. Even if it's just a pointer to a previous thread I didn't enter the right search terms to find.

 

[RatsoW8]

You didn't give any specifics about the radio so assuming that the radio is a stock FCC type accepted class "D" CB radio and unmodified you are probably seeing the correct output in SSB which is close to 12 watts. What you are seeing also depends a lot of the watt-meter you are using. Is it reading average power or true pep and is it calibrated?

 

[Captain Kilowatt]

Switch to AM and see what the carrier level is. RatsoW8 could be correct. I had one of those radios many years ago marketed under the name Iroquois-40 by a company called Cardon which was a division of Midland. It had wood grain on the front instead of solid black.Great radio. On the chassis there is a small metal screw adjustment which is connected to a wire-wound pot. that is the power output adjustment control BTW. It affects both AM and SSB power because it adjusts the voltage to the finals. My radio would run 25 watts pep on SSB and 10 watts of AM carrier quite easily.

 

[TM86]

You didn't give any specifics about the radio so assuming that the radio is a stock FCC type accepted class "D" CB radio and unmodified you are probably seeing the correct output in SSB which is close to 12 watts. What you are seeing also depends a lot of the watt-meter you are using. Is it reading average power or true pep and is it calibrated?

You're right, it was a paltry bit of information. Not that it matters as the good Captain had the answer in the very next post.

For the record, it is a US FCC 40 Channel type accepted Class D radio.

I had the radio hooked to a cheap Radio Shack power/SWR meter, uncalibrated, model 21-524. It's not exactly an LP-100A, but it's what my budget would allow at the time I bought it. I don't trust the readings to be highly accurate, but I have used the same meter with other radios and the readings are all about what I expect with those. I had the meter set in "PEP" mode, which isn't a true PEP reading, but it's what I've got.

To the back of the meter I attached a small 50 ohm resistive dummy load. Another Radio Shack cheapie. I probably won't buy their stuff again.

With this info anyone who cares to duplicate my setup can, but why would you want to?

 

[TM86]

Switch to AM and see what the carrier level is. RatsoW8 could be correct. I had one of those radios many years ago marketed under the name Iroquois-40 by a company called Cardon which was a division of Midland. It had wood grain on the front instead of solid black.Great radio. On the chassis there is a small metal screw adjustment which is connected to a wire-wound pot. that is the power output adjustment control BTW. It affects both AM and SSB power because it adjusts the voltage to the finals. My radio would run 25 watts pep on SSB and 10 watts of AM carrier quite easily.

That was the secret sauce, my good Captain. I cranked the AM carrier up to about 10 watts, then backed it down to 5. Checked my SSB output and my crummy little meter showed 12 to 15 watts on a "whistle tone". Hate doing it that way, but you go with what you got.

Thanks!

 

[Robb]

Might turn the dead key down to 3w and see if you can't get 12w PEP on AM.
I usually tune the output coils in SSB mode if the radio has sideband.

 

[Captain Kilowatt]

Might turn the dead key down to 3w and see if you can't get 12w PEP on AM.
I usually tune the output coils in SSB mode if the radio has sideband.

Why do you do that? You are tuning for frequency not mode. I find simply transmitting a steady carrier is easier.

 

[Robb]

Why do you do that? You are tuning for frequency not mode. I find simply transmitting a steady carrier is easier.

The service manual says to do it in SSB using a two tone test signal. The SINAD program I use has a single 1khz tone, so I use that . . . need to get a program that will do a two tone that can adjust the freq of each tone . . .

 

[Captain Kilowatt]

The service manual says to do it in SSB using a two tone test signal. The SINAD program I use has a single 1khz tone, so I use that . . . need to get a program that will do a two tone that can adjust the freq of each tone . . .

Oh OK You must be talking about an alignment too then. That would include SSB circuits. I thought you were just referring to the final output stage.

 

[Robb]

Well; yeah. There are a series of coils that feed the PA section that comes from the mixer chip. Peaking these coils - as you know - maximizes the match between the PA stage and the mixer output. That is at the core of the real radio peaking if done right. After that I set the DK level - done! . . .

 

[Captain Kilowatt]

Yeah OK that's cool. I just had visions of the filter circuits being screwed. Both figuratively and literally.

 

[Robb]

You're right, it was a paltry bit of information. Not that it matters as the good Captain had the answer in the very next post.

For the record, it is a US FCC 40 Channel type accepted Class D radio.

I had the radio hooked to a cheap Radio Shack power/SWR meter, uncalibrated, model 21-524. It's not exactly an LP-100A, but it's what my budget would allow at the time I bought it. I don't trust the readings to be highly accurate, but I have used the same meter with other radios and the readings are all about what I expect with those. I had the meter set in "PEP" mode, which isn't a true PEP reading, but it's what I've got.

To the back of the meter I attached a small 50 ohm resistive dummy load. Another Radio Shack cheapie. I probably won't buy their stuff again.

With this info anyone who cares to duplicate my setup can, but why would you want to?

Just thought I would add something to help a bit. You can use that cheap RS meter, just keep in mind that it cannot read any PEP accurately. But it can still show changes either up or down that still makes it useful as a tool to see if the state of tune is changing.

However, I would dump that cheap dummy load in a heartbeat and get a better load. You don't want/need a dummy load that is going to heat up and thereby change its resistive quality. As that will affect the reading and reliability of your test. You need a stable load for getting better measurements - even if you change out anything else. You can make a dummy load and put it in a can with mineral oil and keep it very cool/stable - and do it pretty cheap . . .