[TowerTalk] coax stubs /bandpass filter

[Richard (Rick) Karlquist]

I've given up trying to make the lumped element argument to hams.
Too hard to change belief systems.
Coax stub filters are firmly entrenched ham radio folklore,
regardless of whether they make engineering sense.
They are seldom if ever used for filtering in commercial HF radio systems.

BTW, the argument about the Q being "too high" goes away
with the realization of the difference between loaded and unloaded
Q.  The harmonics property is only useful if you need to pass
the frequencies between the harmonics, which is not necessary
for ham use.

Rick N6RK



jimlux wrote:
> Along a similar note..
> 
> The stub is just a moderate Q resonator that's easy to fabricate.  Why 
> not put a lumped LC shunt trap across the feedline?
> 
> Too hard to get the Q low enough?
> Doesn't have the nice harmonics property? (a coax stub for 40 is also a 
> stub for 15)
> 
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