Lee,
There is nothing wrong with taking readings at the bottom of the
transmission line, you just need to understand what they really mean. If you
have a reasonably short, reasonably low loss transmission line, and you
measure an SWR of 1:1 at the bottom, the SWR at the top, which is what you
want to know, will be very close to 1:1.
OTOH, if you measure an SWR that is higher than 1:1, or you have a long or
lossy transmission line, the loss and impedance transformation properties of
the line itself will make the readings hard to interpret. They will still be
valid readings, they just won't tell you what you want really want to know
about what's happening at the antenna.
If you have full impedance data (with sign of reactance), and know the
electrical length of the line, you can determine the actual Z and SWR at the
top through the use of a Smith chart, or a program such as TLW, that comes
with recent editions of The ARRL Antenna Book. I'm sure there are other
programs as well.
If you have access to QST, take a look at my article: Feb 2007 - QST (Pg.
63)
I Know What's Happening at the Shack -- What's Happening at the Other End of
my Feed Line?
Regards, Joel Hallas, W1ZR
Westport, CT
-----Original Message-----
From: tentec-bounces@contesting.com [mailto:tentec-bounces@contesting.com]
On Behalf Of kc9cdt@aol.com
Sent: Sunday, November 20, 2011 6:51 PM
To: tentec@contesting.com
Subject: Re: [TenTec] Antenna-Analyzer
Question,
Is it OK to use ant of the HH analysers from the shack using the normal
feedline?
OR do I have to be right at the antenna....?
73,
Lee
-----Original Message-----
From: Richards <jruing@ameritech.net>
To: Discussion of Ten-Tec Equipment <tentec@contesting.com>
Sent: Sun, Nov 20, 2011 6:48 pm
Subject: Re: [TenTec] Antenna-Analyzer
Rick -- You seem to be laboring under a misconception. I think you are
confusing it with the AIM models that are computer based only.
The RigExpert AA-230 and related models are about the same size as an
MFJ 259 and so they go right up the tower with you, but they can
memorize the data for later download to the computer. They are the
best
of both worlds.
See what I have here:
http://www.rigexpert.com/index?s=aa230
Just MY take.
====================================K8JHR =========================
On 11/20/2011 4:45 PM, Rick - DJ0IP / NJ0IP wrote:
, and I need a small, portable
> device that I can connect and do a quick check of the antenna,
outside. I
> don't want to take a PC with me outside.
>
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