[Top] [All Lists]

Re: [TowerTalk] Stubs and rx noise

To: "VE5ZX" <>,"towertalk" <>
Subject: Re: [TowerTalk] Stubs and rx noise
From: "Michael Tope" <>
Date: Thu, 16 Dec 2004 04:48:01 -0800
List-post: <>
----- Original Message -----
From: "VE5ZX" <>

> There is no increase in noise when the rx is either terminated in a 50 ohm
> load or left open.

Okay, you had said:

<<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>>

perhaps you meant to say "4/0/0" or you changed the meaning of the
sequence to be "no stubs/stubs/dummy load" instead of
"14AVQ/50 ohm RX term/open RX term"

In any case, since your using a vertical for the second radio,
you might have a common-mode coupling problem between
the two rigs. Is the vertical ground mounted with a good
radial system or is it up in the air with a few elevated radials?
Do you have a current balun or any kind of RF feedline choke
in series with the feedline for the 14AVQ?

Also, have you checked the 2nd rig for fundamental overload?
The stubs on the TX side will cut down broadband noise from
the transmitter in the receive band, but they won't change the
amount of fundamental energy hitting the front-end of that 2nd
rigs receiver. You can check to see if the receiver is folding by
putting a step attenuator in front of the receiver. If the front-end
is folding it will have a sharp (e.g. non-linear) threshold below
which the noise goes away (e.g. 10dB attenuation causes
the noise to drop much more than 10dB). If that turns out to
be the problem, then you can fix it with the right kind of stubs
on the RX side or one of the various LC bandpass filter
solutions that are out there (Dunestar, ICE, W3NQN, etc).

Those are the kinds of things I would look for, Sylvan.

Good Luck!

73 de Mike, W4EF..........................


See:  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

<Prev in Thread] Current Thread [Next in Thread>