[TowerTalk] Stub tuning

[Jim Lux]

At 03:26 AM 9/12/2005, David Robbins wrote:

>The location of the stub may change the tuning due to some reactance
>introduced when the stub is slightly off its tuned point, but the correct
>length is measured from the T connector where it is inserted not including
>any other cable between it and the amp or other equipment.  Stubs can be
>T'ed in anywhere it is convenient along the feed line.
>On Behalf Of Tom Osborne
> > Sent: Monday, September 12, 2005 04:35
> > To: Towertalk
> > Subject: [TowerTalk] Stub tuning
> >
> > HI TT'ians
> >
> > I'm trying to get the stubs hooked up here.  I cut some and they are right
> > where I want them to be, using the MFJ tuner option.
> >
> > I cut the 20 meter one right at the meter and wanted to hook them up on
> > the
> > outside of my antenna switch.  Going from the rig, there is about a 3 foot
> > cable to the MFJ tuner/swr bridge.  Going from there is about a 3 foot
> > cable
> > to the homebrew antenna switch.
> >


If you have Excel, then XLZIZL from AC6LA (free!  google for it) is a great 
way to analyze stubs.  You can put in all your feedlines, and the stub, and 
look at VSWR plots (or Smith charts) and fool around with changing lengths 
and see what happens.