Jim, AC6TK says:
>Putting an outboard filter AFTER the internal tuner can give you problems
if you have a reactive or
>mismatched load
A common misconception is that mismatching a filter reduces the
attenuation. Mismatching has very little effect on the stop band, and most
effect on the passband (usually increased ripple). A bigger difficulty when
mismatched is that the impedance seen at the input of the filter in the
passband can be changed drastically from the load impedance that the
transmission line offers. This can mean that the transceiver's internal
transmatch can no longer handle the load. Another problem can be that the
voltage build up in the filter can lead to arcing, or the current can be
such as to cause melting of solder joints (but this is usually at power
levels above 100watts)
Having said which, I have an MFJ LPF which regulary handles 1Kw in 2.5:1 SWR
without any problem - it, I hasten to add, a tube PA, which is more
forgiving on SWR..
73
Peter G3RZP
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