[TowerTalk] Tuning Antennas with the MFJ-259

[W0MU Mike Fatchett]

Yes you are correct.  With the dipole you can lower the ends and change the
length from the ground.  Keep both sides of the dipole or Inverted V the
same...i.e. cut equal amounts from each side when adjusting for lowest swr.

If it is an Inverted V the actual angle of the V can influence the lowest
SWR you can get.  Find the dip and move the dip to where you want to operate
and then you can vary the angle of the V for best SWR if necessary. 


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-----Original Message-----
From: towertalk-bounces at contesting.com
[mailto:towertalk-bounces at contesting.com] On Behalf Of AD5VJ Bob
Sent: Saturday, March 28, 2009 11:00 PM
To: 'jimlux'; 'Richards'
Cc: towertalk at contesting.com; K7LXC at aol.com
Subject: Re: [TowerTalk] Tuning Antennas with the MFJ-259

Well one of the antennas I will be working on in the morning is going to be
an 80 Meter dipole, but I can only get it up here at abt 30' then I will be
taking it and putting it up at around 60 feet, so it sounds like I want to
tune it high and expect the dip to move lower in frequency at the 60 foot
level (maybe a few Khz per 10' in height or so).

If I am understanding all the input correctly, the swr curve will be less
affected by the ground effects and therefore seem longer (more inductive) as
I raise it higher above ground (lessening the capacitance).

Bob AD5VJ 

> -----Original Message-----
> From: towertalk-bounces at contesting.com 
> [mailto:towertalk-bounces at contesting.com] On Behalf Of jimlux
> Sent: Saturday, March 28, 2009 10:24 PM
> To: Richards
> Cc: towertalk at contesting.com; K7LXC at aol.com; rtnmi at sbcglobal.net
> Subject: Re: [TowerTalk] Tuning Antennas with the MFJ-259
> 
> Richards wrote:
> > Gee...  that does not sound like you are tuning it on the work 
> > bench...  I think this is more of a vote for "no... you should hang 
> > your antenna to tune it" - than it does a Yes you can.
> > 
> > Or do I misinterpret your statement here?
> > 
> > ================   K8JHR  ======================
> > 
> > K7LXC at aol.com wrote:
> >>  
> >>         Once you see a dip, then  you can install the
> antenna. Using
> >> a tramline, you can run the antenna up  and take a
> measurement. Then
> >> you can lower it and make any adjustments to tune  it. Run
> it up and
> >> down as many times as you need and you're good to go.
> 
> 
> 
> 
> if you've got enough area around it, pointing it straight up, and 
> having it 6 feet or so off the ground, will give results very close to 
> what it will read up on the tower.  Think of the "active volume" of 
> the antenna as being everything within say, 1/4 wavelength.  For a 20m 
> band antenna, that's around 15-20 feet.  It's pretty practical to 
> strap it to
>   a 2x4 or or something and hold it up with a step ladder.
> 
> As others have pointed out, you're not looking to adjust to a gnat's 
> eyelash, you're really checking to see if it's close to what you 
> expect (e.g. legions of stories about folks getting the traps in the 
> wrong order on trapped antennas, or forgetting to hook up a wire to 
> the balun,
> etc.)
> _______________________________________________
> 
> 
> 
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> 

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