----- Original Message -----
From: "VE5ZX" <email@example.com>
To: "towertalk" <firstname.lastname@example.org>
Cc: "(VE5UF) Doug Freestone" <email@example.com>
Sent: Wednesday, December 15, 2004 6:20 PM
Subject: [TowerTalk] Stubs and rx noise
> I have been playing with a small SO1.5 setup for my low power station. I
> have an F12 C31XR tribander, EF240S and I use my tower as a vertical on
> 80/160. I have a 14AVQ that I am using as my second antenna.
> I built some 80, 40, 20 and 10m 1/4L stubs from RG6 using an Autek VA1. I
> checked each stub by putting it in the rx feedline and I found that on the
> appropriate band it gave me about 6 S units of attenuation.
> According to the information at http://www.qsl.net/ak6r/coax_stubs.htm for
> 10m I should use a open 40m and 20m stub in the tx feedline in order to rx
> on 10, 15 and 40. I did that and found it made no difference to the noise
> in the rx. Here are some measurements I made.
> If I tx @100 W on 10m and rx using the 14AVQ vertical, a 50 ohm resistor
> an open antenna terminal the noise in the rx is 4/0/0 S units,
Sylvan, on what band were you listening in this case? And when you were
listening on the 14AVQ what was the noise level when you weren't
> If I tx @ 100W on 10m and rx on 15/20/40 the noise in the rx is 4/4/0 S
> units with and without the stubs in the tx feedline.
> I presume that the noise in the rx is getting there via some other route
> other than antenna coupling. How can I isolate the noise path?
Sounds like you have a sneak path. If you are seeing a 4 S-unit
increase in noise when you transmit even when the 2nd rig is
terminated into a dummy load, then something is wrong. I would
try to separate the two rigs as much as possible (e.g. eliminate
as many common connections as possible) and then repeat the
tests. There is no reason that you shouldn't be able to completely
eliminate the interstation QRM, especially at 100 watts tx power
(except where you are listening on an exact harmonic of the other
73 de Mike, W4EF.......................
> Sylvan Katz - VE5ZX
> Saskatoon, SK
> See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless
Weather Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any
questions and ask for Sherman, W2FLA.
> TowerTalk mailing list
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather
Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions
and ask for Sherman, W2FLA.
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