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Re: [TowerTalk] coax stubs /bandpass filter

To: "Tower and HF antenna construction topics." <>
Subject: Re: [TowerTalk] coax stubs /bandpass filter
From: jimlux <>
Reply-to: "Tower and HF antenna construction topics." <>
Date: Tue, 30 Mar 2010 17:50:49 -0700
List-post: <">>
Richard (Rick) Karlquist wrote:
> 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.

I think the engineering appeal (such as it is), is ease of fabrication. 
  Everyone has scraps of coax around, and the tuning is easy.. hook it 
up and grab a pair of garden shears and start cutting.  You could do it 
empirically (Keep cutting until the offending signal is "nulled") and in 
situ (e.g. field day).

> 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. 
I figured that was the case, but thought maybe there's something else 
going on (interaction with the Tx or Rx Zs?)


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