> The label says 136-174Mhz And was set to 153.92.
> 10-20W In=200-250W Out.
> [EMAIL PROTECTED] (Fuse is 40A)
> 120VAC for cooling fan only
> P/N PA3-1FF and hand etched the letters "RF"
>
> It appears to be similar to the other PA3's according to manuals
> found on Repeater-Builder Website but with more power.
>
> I want to use it as A 2 Meter HAM Linear.
> I was thinking that will not work since the output freq is
> set regardless
> of the input freq.
First, that's not a linear amp, it's class C. Please don't attempt to use
it for modes that require good linearity (such as SSB).
Every TPL VHF or UHF amp I've ever worked on had variable capacitors in both
the input and output matching networks. The PA strips should be tunable
across the rated range (136-174 MHz). I don't recall whether or not the
values of the components in the harmonic filters are varied depending on
what frequency the PA was ordered for. If I were moving the amp that far
from its factory-tuned frequency, I would test the harmonic filter itself to
verify that the match is good and insertion loss is acceptable, and then
measure the harmonics with the amplifier operating and the filter in-line.
The basic tuning of these amplifiers is straightforward. Tune the input
stages for best balance between maximum return loss (least input VSWR) and
maximum power out. The two should align closely. The output should be
tuned for peak efficiency, which should also closely align with maximum
power out.
Since you have multiple gain stages, both in series (driver) as well as in
parallel (finals), there will be some interaction. Start out tuning at
below-normal drive levels (around 5 watts) to get the tuning in the
ballpark, then increase the drive slightly and re-tune. Keep your four eyes
fixed on the spectrum analyzer, input power meter, output power meter, and
DC ammeter while tuning. Don't let any parameter get too far out of whack
lest you risk letting the smoke out somewhere.
--- Jeff WN3A
