>The SWR/resonant freq. readings were taken with an MFJ-259 Antenna
>Analyzer connected to the RF INPUT of the amp and the amp switched
>to the TRANSMIT mode, so the analyzer would 'see' the appropriate
>load.
This is a mistake.
An amplifier other than one in class A operation needs to be "driven"
into its active region. As a result, the input impedance of the device
varies substantially over the range of the drive cycle. Look at it
another way: the input impedance varies with the power applied.
Just keying the amp shows one nothing about the amps "true" input
impedance. If you want to see where the amp might truly be resonant,
connect the amp into a dummy load and to a transceiver capable of out of
ham band operation. Then key up at different spots across the band.
That's a better "quick" test.
The MFJ-259 puts out so little RF that there is no possible way that it
can drive the tubes into their active region. So your measurements are
virtually meaningless.
Why did they look good on 80-20? Well, perhaps dumb luck. But as you go
higher in frequency, it gets harder and harder to become "lucky."
73,
Jon
KE9NA
-------------------------------------
Jon Ogden
KE9NA
http://www.qsl.net/ke9na <--- CHECK IT OUT! It's been updated!!!!!
"A life lived in fear is a life half lived."
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