Hello, I have a little used MFJ-492 electronic keyer that I've decided to
put to good use as an amplifier tuner. (This is my first amp). The keyer
defaults to a 50% duty cycle and I would like to get this down to around 10
or 20 percent. Any suggestions on what weight to use? This keyer is
adjustable from 5 to 95 percent weight...I do not have a scope so would have
to guess by ear. Thanks for the help.
Craig KB8FGC

Hi, Craig

Sounds like 50% keyer "weight" would be the same as 50% duty factor.

If you have an analog Ohmmeter, you can use that to check
the weight. Assuming the red lead of the Ohmmeter puts out + volts,
connect it to the + keying output ("direct" output
of the MFJ-492), with the black Ohmmeter lead to ground.
With Ohmmeter set to RX100, set keyer to "tune" and adjust
Ohmmeter to zero Ohms. Key the keyer at high speed, 50% weighting,
the Ohmmeter pointer should be at half-scale of the Ohmmeter
with a string of dits.
20% weighting should be 20% of full scale.

If your analog Ohmmeter scale shows 20 Ohms at half scale,
it may indicate about 100 Ohms at the 20% of full scale point.

If you don't have a scope to use the pulse tuning method, do you have
a peak-reading rf Wattmeter?

73,
Ed Knobloch


Craig wrote:
Hello, I have a little used MFJ-492 electronic keyer that I've decided to
put to good use as an amplifier tuner. (This is my first amp). The keyer
defaults to a 50% duty cycle and I would like to get this down to around 10
or 20 percent. Any suggestions on what weight to use? This keyer is
adjustable from 5 to 95 percent weight...I do not have a scope so would have
to guess by ear. Thanks for the help.
Craig KB8FGC