[TowerTalk] coax stubs

[David Robbins K1TTT]

Stubs are fairly wide band pass and reject filters.  Much more than a ham
band wide.  You have to go to multi-pole lumped filters or crystal filters
to get in band rejection.

The 'Single Coax Stub Analysis' link at:
http://www.k1ttt.net/technote/techref.html#filters
Shows just how wide a typical stub is as a filter.


David Robbins K1TTT
e-mail: mailto:k1ttt at arrl.net
web: http://www.k1ttt.net
AR-Cluster node: 145.69MHz or telnet://dxc.k1ttt.net
 

> -----Original Message-----
> From: towertalk-bounces at contesting.com [mailto:towertalk-
> bounces at contesting.com] On Behalf Of Bill Coleman
> Sent: Thursday, June 15, 2006 04:15
> To: David Hachadorian
> Cc: Towertalk Reflector
> Subject: Re: [TowerTalk] coax stubs
> 
> 
> On Jun 14, 2006, at 12:34 AM, David Hachadorian wrote:
> 
> > Well, a shorted .25 stub for 20 passes 20 and rejects 10,
> > not very valuable.
> >
> > Here is a better trick to remember:
> > 40m .25 stub (23' @ vf=.66)
> > shorted, passes 40/15, rejects 20/10
> > open, passes 20/10, rejects 40/15
> > Make one stub, use a switch to open/short the tail.
> 
> How broad are these stubs? Wouldn't a 1/4 wave stub tuned for 7.1 MHz
> only pass 15m at 21.3 MHz? Can they practically pass/reject the whole
> band?
> 
> Bill Coleman, AA4LR, PP-ASEL        Mail: aa4lr at arrl.net
> Quote: "Not within a thousand years will man ever fly!"
>              -- Wilbur Wright, 1901
> 
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