MAIL FROM THE WUN LISTSERVER

SOME THOUGHTS ON NOISE BLANKING



Date: 24 Dec 1997 01:02:24 +0100
From: (Ralf R. Radermacher)
Subject: Re: [WUN] noise

On 23.12.1997 at 03:32:33, (lora humelsine) wrote
re: [WUN] noise

lh> A local store about a block from my house has just put up a glitzy new 
lh> neion sign and the noise from it is driving me nuts.  I can null it out 
lh> using the number one noise blanker on my r5000 but when a strong signal 
lh> comes through it is badly distorted.  I am thinking about ordering a JPS
lh> ANC 4 antenna noise reduction unit.


Although this reply is a bit longer I've decided to post it to the list as
it might be of general interest.

Doing something about interference ahead of the receiver input is
always a good start. But how about taking things one step further and
eliminate the noise before it actually reaches the antenna? I take it that
you're in the U.S. Now, I don't know the legal situation at your end but
I'd look for a popular AM radio station whose reception at my QTH were also
affected and then call in the authorities (FCC in your case) to have them
tackle the problem at the very source, i.e. the neon sign itself. In
my experience, authorities are much more responsive to complaints about
interference to broadcast reception than if you tell them that you're
having trouble listening to some odd low-power Volmet station at the other
end of this planet. Still, it can't possibly be right that this thing
generates so much noise. I live smack in the city centre of Cologne and I
have literally thousands of these signs within a radius of a mile from my
QTH and, yes, they do cause some noise but none of them to the extent that
they affect my sanity. Well, unless I just haven't noticed, myself..... ;-)

If this approach fails, a noise cancelling unit would be your second-best
choice. I don't know about the ANC-4 but I've been using a MFJ-1026 for a
bit over a week now which is (a) a bit less outrageously expensive and (b)
quite good at reducing noise radiated by mains-powered equipment.

There is still another option. Take a look at:

http://users.aol.com/warmspgs/gate1b/gate1b.htm (Discontinued Link!)




(try this one:)

KA5QEP's  Synchronous Noise Blankers Revisited  - via LWCA 


(and this one:)

KA7OE's  Line Synchronous Noise Blanker  


There, you'll find a description of a 'synchronous noise blanker', a
special circuit that also supresses noise from mains-operated sources
*ahead* of your receiver. Unlike the ANC-4 or MFJ-1026, this one only helps
with this special kind of noise, so it might be worth looking at if you'd
buy one of the more costly noise cancellers only because of this single
source of interference. The author claims a 60 to 80 dB reduction of
mains-synchronous spike noise. Do note, however, that the (FT-50) toroid
specified there is intended for VLF/LF and you'll need to use one of the
usual variety for MF/HF.


Do let me know how you get on.

Cheers and season's greetings,
Ralf

--
Ralf R. Radermacher - DL9KCG                  Koeln/Cologne, Germany

RX:   EKD 300 & EKD 100 + EZ 100 RTTY demodulator/diversity unit,
Ant:  Rohde&Schwarz HE011, Datong AD370, GAP Titan,
      home-made active vertical 3 kHz to 100 MHz
Comp: Amiga 3000T/060/50 MHz  CV64/3D  ScanMate
--
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