[TowerTalk] Stubs and rx noise

[VE5ZX]

 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 and
an open antenna terminal the noise in the rx is 4/0/0 S units, respectively.

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?

tnx

Sylvan Katz - VE5ZX
Saskatoon, SK