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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: "Tom Osborne" <>
Reply-to: "Tower and HF antenna construction topics." <>
Date: Tue, 30 Mar 2010 18:59:21 -0700
List-post: <">>
Hi Rick

Doesn't it take a lot more 'tuning stuff' to make lumped elements than it 
does to make stubs?  All I have here in the way of test equipment is an MFJ 
259B analyzer and a VOM :-)  Works good for making stubs.

I remember when I made some mark/space filters for some TU's that I built 
some years back, I needed a signal generator, o'scope, and a frequency 
counter.  All that stuff is gone now.  73

> 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


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