More on Noise

[Andre Kesteloot]

-------- Original Message --------
Subject: Re: LF: Noise
Date: Thu, 09 Jan 2003 11:22:17 +0100
From: Rik Strobbe <rik.strobbe@fys.kuleuven.ac.be>
Reply-To: rsgb_lf_group@blacksheep.org
To: rsgb_lf_group@blacksheep.org


 >Apart from that, can anyone tell me why local noise IS a
 >vertically-polarised E-field problem? I can intuitively (I think)
 >understand that it would be E-field since it is primarily a 
high-impedance
 >phenomenon; but why VERTICALLY-polarised? If it's radiated from local
 >house wiring etc surely it should be randomly-polarised and just as
 >evident on horizontally-polarised antennas? I have a 30 m vertical I
 >occasionally use on 80m and a horizontal dipole for 80m near it. VERY
 >often there is so much noise on the vertical I can't even hear my local
 >net; on the horizontal at the same time there is only the faintest trace
 >of noise and everyone is easily audible.  Same on 160m. All the texbooks
 >agree local noise is vertically-polarised but not one of them explains 
why.

Hello Walter,

Maybe "local noise" is vertically polarized because it is generated
"against ground" : the wiring in the house acts as antenna, the ground as
counterweight. As far as I got it any "against ground" fed antenna is
vertically polarized, a nice example is the DDRR antenna that is a
completely horizontal construction and yet a vertical polarized antenna.
But there might be another reason for the high noise levels on your 
vertical :
Years ago I contructed a full-sized Marconi antenna for 7MHz. In an attempt
to be smart I connected just a few short radials and used the "house
grounding stake" as counterweight. That worked fine on TX (antenna
resistance was very close to 36 Ohm) but I had a tremendous noiselevel on
RX. Disconnecting the "house grounding stake" solved the noise problem, but
I had to add more and longer radials to get the antenna impedance back to
36 Ohm.

73, Rik  ON7YD