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Re: [TowerTalk] Using a dip meter

To: "Jim Lux" <>, "Jeff Carter" <>
Subject: Re: [TowerTalk] Using a dip meter
From: "Jim Miller" <JimMiller@STL-OnLine.Net>
Date: Thu, 20 Mar 2008 19:14:37 -0500
List-post: <">>
There's another difference - the dollars are a LOT larger on those than on
the GDO.
73, Jim

----- Original Message ----- 
From: "Jim Lux" <>
To: "Jeff Carter" <>
Cc: <>
Sent: Thursday, March 20, 2008 6:33 PM
Subject: Re: [TowerTalk] Using a dip meter

> Jeff Carter wrote:
> > I've been following this thread with interest, largely because I'm
> > ignorant about the utility of these meters.  Jim, your description
> > fits with what I had concluded about them, that being if you had
> > pretty much anything else to use, it would be better.  I understand
> > how they work but using a GDO always seemed pointless.
> >
> > I have seen these things on eBay for years, but I still cannot think
> > of a single instance where it would be of more utility than more
> > modern antenna tools, so I never bought one.
> >
> > My question is, am I wrong?  Is there some situation I have not yet
> > encountered where only a GDO will do?  Jim, you said that for some
> > systems it's convenient.  I can't picture one for the life of me.
> The GDO has two aspects that are convenient:
> 1) It's inherently a narrow band detection process, so interfering
> signals (a real issue if you're trying to dial in a 160m antenna and
> there's a pesky AM broadcast station near by)
> 2) It's not oriented towards a 50 ohm system in particular.  You can
> adjust the coupling ratio to suit the measurement (granted, more an art
> than science).
> >
> > I usually use a HP network analyzer for general things, and the little
> > Autek boxes for spot checks.
> You should be able to use the VNA.. Set it up to measure S11, then run
> your coax up to a coupling network of some sort.  In theory, you'd want
> a transformer to transform the 50 ohms to whatever the loop resonant R
> would be, but in reality, since you're going to be using loose coupling,
> that will set the magnitude. I've used some turns of magnet wire on a
> BNC connector (and you can add and remove turns by hand)  You'll see the
> bump in S11 magnitude at the resonant frequency of the system under test.
> (of course, the VNA's probably not handheld.  Anritsu has a handheld
> (2hands) device that does this sort of thing, though, if you have a few
> tens o'kilobucks laying around.  It's pretty neat)
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