W6RCL / ALAN KAUL
A "no-mod" MOD!!!
Simple Circuit to Enable Any Rig Equipped With ALC to Reduce Power to Milliwatts!
Be sure to connect a cable from the jack you've just wired to the ALC input on the back of your transceiver (usually an RCA jack).
How it works
The battery is wired to produce a negative voltage (very much like the negative voltage an amplifier developes when the input is overdriven or distorted). The voltage is varied by the potentiometer, and connected to the ALC input of your transceiver. As the negative voltage increases, the ALC in the transceiver or transmitter reduces output.
The control can be used to set the power of an ALC-equipped rig from any level between the rated output of the transcveiver (high) and milliwatt levels (low). It is great for adjusting the output of a commercially-built QRO rig -- because you don't even have to open the case, or modify the rig permanently. When you are done running QRP, just unplug it!
Note: If the 1.5v battery doesn;t generate enough ALC voltage to get your rig to a low enough power level, try two batteries in series, or three! KEEP EXPERIMENTING because you can't hurt the rig!!
WARNING:
If left plugged in, the battery will discharge thru the pot. Either unplug it or remove the battery or install a switch in series with the battery (between the + terminal and ground, or between the - terminal and potentiometer).
One more bit of advice: check your power output ever 30-40 minutes or so with a powermeter, scope, etc. Beacuse the power level on my rig tends to self-adjust. I usually start running about 5W and then it's down to 1W, and the only clue I get is it seems to become harder to work other stations.
Back to W6RCL/QRP!
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E-mail:w6rcl@amsat.org
72, de Alan
Visitors since 28 February 1998: 
How it works
The battery is wired to produce a negative voltage (very much like the negative voltage an amplifier developes when the input is overdriven or distorted). The voltage is varied by the potentiometer, and connected to the ALC input of your transceiver. As the negative voltage increases, the ALC in the transceiver or transmitter reduces output.
The control can be used to set the power of an ALC-equipped rig from any level between the rated output of the transcveiver (high) and milliwatt levels (low). It is great for adjusting the output of a commercially-built QRO rig -- because you don't even have to open the case, or modify the rig permanently. When you are done running QRP, just unplug it!
Note: If the 1.5v battery doesn;t generate enough ALC voltage to get your rig to a low enough power level, try two batteries in series, or three! KEEP EXPERIMENTING because you can't hurt the rig!!
WARNING:
If left plugged in, the battery will discharge thru the pot. Either unplug it or remove the battery or install a switch in series with the battery (between the + terminal and ground, or between the - terminal and potentiometer).
One more bit of advice: check your power output ever 30-40 minutes or so with a powermeter, scope, etc. Beacuse the power level on my rig tends to self-adjust. I usually start running about 5W and then it's down to 1W, and the only clue I get is it seems to become harder to work other stations.
Back to W6RCL/QRP!
click
E-mail:w6rcl@amsat.org
72, de Alan
Visitors since 28 February 1998:
WARNING:
If left plugged in, the battery will discharge thru the pot. Either unplug it or remove the battery or install a switch in series with the battery (between the + terminal and ground, or between the - terminal and potentiometer). One more bit of advice: check your power output ever 30-40 minutes or so with a powermeter, scope, etc. Beacuse the power level on my rig tends to self-adjust. I usually start running about 5W and then it's down to 1W, and the only clue I get is it seems to become harder to work other stations.
Back to W6RCL/QRP!
click
E-mail:w6rcl@amsat.org
72, de Alan
Visitors since 28 February 1998:
72, de Alan
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Visitors since 28 February 1998:
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