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Can anyone tell me the proper keydown output for a Henry 2006a six meter amplifier running a singel 3cx-800a tube? Mine is doing 650 watts output, keydown with 15 watts drive, 35mA grid current, and 400mA on the plate. Seems to be doing what the manual calls for, however I have a friend that has one of these amps and his is doing more power with less Grid current, I suspect his amp has been modified but don't know for sure. Thanks for you input. Tom K9TB

Hello Tom,

You've provided some information on your Tempo 2006A 6 meter RF amplifier as far as the Grid and Plate Currents and RF Drive but you haven't provided the Plate High Voltage DC reading. I see you've got a later version 2006A amplifier using a single 3CX800A vacuum tube in the Ground Grid configuration.

When Henry Radio first started selling these High Power RF Amplifiers in the 1970s, they started out as Tempo 6N2 using a pair of 3CX400A / 8874s and capable of covering 50-54 MHz and 144-148 MHz using the Ground Grid configuration on both bands. Back then the Finals were rather inexpensive from Eimac as you weren't required to put a second mortgage on your house just to replace the valves. Henry Radio had to stop manufacturing the 6N2 because it did not meet the current FCC emission standards on 6 meters.

Henry Radio then came out with the Tempo 2000 Series Single Band RF amplifiers: 2006A 50-54 MHz, 2002A 144-148 MHz, 2003A 220-225 MHz and 2004A 430-450 MHz. All of these were Ground Grid and used a pair of the 3CX400A / 8874s vacuum tubes. Into the 1990s Henry Radio set up Radio Dan to start manufacturing these same RF amplifiers but using a single Svetlana (Russian Made) RF vacuum tube which are High Mu (Gain) which would cut the manufacturing cost, not required neutralization and produce the same RF Output for a given RF Input Drive. I really believe to produce 1200 RF Watts Output on the Tempo 2006A, you would be required to have 40-50 RF Watts Input Drive.

There's another observation I've made, "if" your RF Input VSWR is above 1.3:1 or higher you will develop Positive Grid Current in Classes AB1 and AB2 Linear Operation so keep the lowest VSWR between your Transceiver and the RF Input on the amplifier. Another item I've noticed with the Svetlana RF vacuum tubes is the Filament voltage. "If" the Filament voltage varies +/- .5 V, the RF Output will vary as much as +/- 10% of the Rated RF Output. It's very important to connect your amplifier's power supply to a known good Primary Power 121 / 240 V AC source with adequate Current available to insure stable operations.

Dan