> As evidenced by the published test figures on, for example, the
> TS2000. Interesting, since modern MOSFET PA's are supposedly very
The TS2000 is not a good example. It is exceptionally poor. It is
one step removed from class C performance.
We have to remember a two-tone test does not show IMD caused
by poor dynamic power supply regulation.
Also AB1 or 2 tetrodes get nasty FAST compared to a GG triode
when overdriven or misadjusted.
> If the linear at full rated power is capable of -30dB rel PEP IMD
> products, then the total IMD power is likely to be (neglecting phasing
> and compensating distortion effects) 27dB down on PEP.
That's right, IMD can add. So the PA must be many times cleaner
than the exciter to not make things worse.
> case the transceiver) needs to be a lot better. That suggests that
> either it needs to run at a lower power output, demanding more gain
> from the amplifier, or needs to be 10 to 20dB better on IMD at the
> rated output. Many transceivers probably need to run around the 25
> watt level rather than the 100 watt level for acceptable overall IMD.
> However, Part 97.317 (a) 3 of the the FCC rules gives us a problem, as
> it requires a 50 watt (mean) drive minimum for an amplifier.
Reducing drive power from an exciter does not always make things
better. Quite often it actually makes things worse.
73, Tom W8JI
FAQ on WWW: http://www.contesting.com/FAQ/amps
Administrative requests: amps-REQUEST@contesting.com