Most RF-spectrum noise generated by TV sets and computers and radiated by the
power line is common-mode noise, and the typical differential-mode (in-line)
power filter will do nothing to suppress it. You need to make a common-mode RF
choke. Get some large ferrite toroid cores (Palomar Engineers as well as
others sell them) and wind the entire power cord of the TV through a couple of
these in series. (In less severe cases, just one toroid may do the trick.) The
toroid needs to go as close to the TV set as possible, as any unshielded
conductor between the toroid and the power supply will still radiate.
You can also encase the whole power cord in clamshell ferrites if you can find
them in the correct size, but I've found this to be less effective than
toroids. The benefit of this method is that you don't have to supply an
extension cord to replace the length of the power cord you wound through the
toroids.
Bill / W5WVO
Brett gazdzinski wrote:
I would ask the people if I could put a filter on the power
line to the TV.
That might reduce or eliminate the QRN.
Maybe get a surge protector/filter setup and convince them
it's a protection device for their investment.
I bought phone filters and installed them on the neighbors on both
sides of my house to eliminate the AM getting in the phones.
I also had to filter an audio system with extended speaker
wires as I came through quite loud even with the thing
turned off. Some caps across the speaker outputs cured it
totally!
Brett
N2DTS
-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] On Behalf Of
Kenneth A. Christiansen
Sent: Tuesday, June 12, 2007 7:50 AM
To: [email protected]
Subject: [Elecraft] K3 Noise Blanker ahead or behind roofing filter?
I have K2 SN 1031 and an IC-746PRO. Last week my next door neighbor
brought home a large screen TV that looks to be the rear projection
type. I didn't pay much attention to it as they unloaded it
but now find
it puts out lots of QRN. It puts out S9 on the PRO 60 HZ QRN
on 20, 15,
10 6 and 2 meters. Those are the bands I have antennas that work. The
noise blanker in theK2 and the PRO both eliminate this bad QRN right
down to the background noise :-) when there are now strong
signals on
the band but when a strong station such as the W1AW code
sessions come
on 20 meters, (20 over 9 in ND), than the K2 using NB1 has problems 5
KHZ or so either side of W1AW. NB2 has problems up to 10 KHZ
either side
of W1AW and the PRO has problems 15 KHZ either side of W1AW
:-( . Is the
noise blanker on the K3 ahead of the roofing filter or behind the
roofing filter. If it is behind the roofing filter buying a
K3 might put
me back on the air :-) but if it is ahead of the roofing filter
than would I have the same problem as the K2 :-( ? I have
looked at the
FAQ part of the Elecraft K3 site and do not find the answer to this
question. I just need a short answer so please do not start a long
thread on my station or observations etc.
73 and thanks for the help.
W0CZ
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