[TowerTalk] SWR Readings

[Ralph Fedor]

Thanks, everyone for your comments.  From the comments, I think my
observations likely relate to other RF sources getting into my antenna
analyzers.  If I run the transceiver and the analyzers directly into a
dummy load with a short coax run, they agree and everything is flat.  I
suspect when my analyzer is hooked to an outside antenna, enough stray RF
from local BC stations, etc. gets in to foul things up as was suggested.
 The amps and transceivers maybe don't "see" this RF as well.  The rigs and
the analyzers do agree as to where the SWR dip is.

As you might expect, this question was triggered by preparing for some
antenna maintenance.  And, I've now found another observation that I'm
wondering about.

I have several runs of 7/8" Andrew Heliax of about 350 feet.  The Heliax
was purchased new several years ago and is labeled, "Andrew Heliax <R> AVAS
- 50."  At the time of purchase I was told the old standard LDF5-50A was no
longer available.  Different connectors are required and I have them
installed.

When I hook a good dummy load to the end of this coax and sweep it with my
analyzer, I notice an SWR "ripple" that starts being apparent at about16.5
MHz with little bumps to 1.3 about every 1000 KHz.  At 28 MHz the SWR
ripple is from a low of 1.3 to a high of 1.5.

I tried the same thing on a run of LDF4-50A that is probably 350 feet long.
 I see the ripple again, but bumps peak at 1.3 and at about a 700 KHz
interval at 28 MHz.

What do I make of these observations?  Are they significantly contributing
to my difficulties in getting a 10 meter antenna to tune properly when fed
with the 7/8" line?

Thanks in advance for any input.

Ralph - K0IR

On Mon, Aug 20, 2012 at 9:42 PM, Ralph Fedor <ralphfedor at gmail.com> wrote:

> If I compare SWR readings on antenna analyzers (two different
> manufacturers) with readings on transceivers or amplifiers (four different
> transceivers, four different amps); the readings on the analyzers always
> appear significantly worse than what I see on transceiver or amp meters or
> LED bars.
>
> Why is that?  Which should I believe?
>
> I connect to the same physical points on the feed lines.
>
> Thanks --
> Ralph - K0IR
>