[RFI] [BULK] Re: Ambient Noise Levels

Jim P jvpoll at dallas.net
Fri Aug 11 20:32:14 EDT 2006

Rauch wrote:
> It doesn't mean the shield actually does anything.
> It doesn't mean the loop is "magnetic".


I would believe you, maybe, if it wasn't for evidence and
measurements and observations like this made with 
test equipment:

Relative strengths of two alternative l.f. antennas:
o E-field antenna the RF Systems LF-520 and an
o H-field antenna the Wellbrook LFL1010.



I then went trawling for a slightly stronger signal and 
found Waterford (callsign WTD) on 368kHz as seen in 
Fig.2(a) with the Wellbrook and Fig.2(b) from the RF 

Once again you can see the noise level from the LFA-520 
[E-field active antenna] is some 30dB higher than that from 
the Wellbrook [the active/amplified H-field shielded loop], 
but of course you can also see that the signal level of the 
Waterford Beacon is 28dB higher from the LFA-520. 

However, if you compare the signal level above noise in 
both cases, 

H-field - the S/N ratio of the Wellbrook is about 26dB while  
E-field - the LFA-520 is about 16dB, 

so the Wellbrook [H-field] provides a better signal to noise ratio 
and a quieter background.

- - - - - - - - - - - - 

Jim P

----- Original Message ----- 
From: "Tom Rauch" <w8ji at contesting.com>
To: <rfi at contesting.com>
Sent: Thursday, August 10, 2006 1:30 PM
Subject: [BULK] Re: [RFI] Ambient Noise Levels

> > Built the magloop unit shown in the link, and was able to 
> > receive on the loop, and transmit on the vertical.  Worked 
> > like a charm.  By rotating the loop, I was able to get the 
> > noise down to an S-4 (during the wintertime-I don't op on 
> > 75 during the summer.)
> Which only means a loop has a null that can be positioned to 
> single direction noise sources.
> It doesn't mean the shield actually does anything.
> It doesn't mean the loop is "magnetic".
> 73 Tom 

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