How does the amp produce trash that is not present at the input?
If your amp does this, it's a piece of trash and should be redesigned,
not 'filtered'.
As for impedance matching 'at the harmonics' .. that's gobbledegook. A
well-designed filter will attenuate as it is designed to attenuate IF it
is inserted between a source and a load with correct impedance at the
frequency IN USE.
Don N8DE
Jim Brown wrote:
> On Tue, 16 Aug 2005 16:10:22 -0400, Don Havlicek wrote:
>
>
>>Why don't hams place the LP filter between the Xcvr and the Amp?
>
>
> Yes. That allows a 100w filter to do the job. Doesn't protect
> against trash from the amp, but it helps the receiver. And if you're
> running barefoot, put it between the amp and the tuner.
>
> BUT -- the same cautions about impedance matching being necessary
> still apply, and that's the fly in the ointment. Not only must you
> be matched at the operating frequency for the filter specs to apply,
> you must also be matched at the harmonics! The chances of that
> occuring are slim to none unless you happen to be working into an
> antenna that is resonant at the harmonics. We DO use some of those,
> but it certainly isn't all that we use, and it would only apply to
> single band filters.
>
> Jim Brown K9YC
>
>
>
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