Henry 2K-4 / 3K-A 2K Classis

Tuning a Henry RF Amplifier



The following RF amplifier turning procedure is only a recommendation. Follow it at your own risk. Reference your RF amplifier's owner's manual for their recommendations.



Tuning Procedure:

Once you reach ~100 watts output from your transceiver, its time to adjust the "LOADING" air variable on the RF amplifier

Additional Comments:

You will need to do this over and over and over and over, again and again and again, until you find the sweet spot where you no longer get any additional RF output out of the amplifier. You will need to do this for each band and frequency. Once you find the sweet spots for each band and frequency, write them down as present numbers.

You should also watch the Ig (Grid Current) meter. If Ig goes to high you could damage the tubes. Adjusting the LOADING air variable will alter the Ig reading. A good rule is don’t drive the tubes greater than 50% Ig on the meter and you should be OK. If Ig gets higher then 60-70% on the Ig meter, you could damage the tubes. For a pair of 3-500Z tubes, normal Ig is about 220 ma. Consult your owner's manual for maximum Ig.

If you hear arcing across the air variables, this means the amplifier is out of resonance. Reduce drive and LOADING so the amplifier is putting out less power and you have a good Ip dip with TUNE. Then increase power input and adjust amplifier LOADING.

You may also want to only key your RF amplifier for durations no longer then one minute. Then let the amplifier cool off for 2-3 minutes before keying again. Depending upon the amplifier, if its out-of-resonance, tuning for longer durations could stress the components and tubes.

You will need to find the sweet spot for each band and frequency where the RF amplifier is resonate. The important thing, start with 20 watts drive and find the spot, then turn up the power, adjust LOADING and find the spots where you have max RF power output.

Once the RF amplifier is correctly tuned, glass tubes will have a nice reddish-orange glow to the plates.


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