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[RFI] Re:trouble shooting techniques for noise

To: <rfi@contesting.com>
Subject: [RFI] Re:trouble shooting techniques for noise
From: Tim Duffy <tduffy@sygnet.com> (Tim Duffy)
Date: Sun, 10 Oct 1999 11:12:46 -0400
Dinsterdog@aol.com wrote:

> Greetings......a couple of weeks ago, I started getting what sounds
> like a
> steady tone of QRM line buzz noise on my NE bevg- at excact 10KHz
> spacing- in
> between, no qrm at all- just a very quiet band to work DX- but the
> buzzing
> falls onto 1.810- 1.820, 1.830 etc........about 1KHz wide- and a small
> spike
> on the scope-The noise is in exact 10KHz steps with no noise
> inbetween- the 10KHz .....and
> it only appears on the 160 meter band- nada on 10-80..............the
> noise
> covers as far down as I can go into the commercial freqs- down to
> about
> 1000KHz and up to 3.000MHz or so before it goes away- fading as I get
> higher
> in freq-
> Anyone have any ideas what this can be??? I thought I'd find right
> away-
> computer switch, cable box transformer etc.....but to no avail- please
> email
> me at dinsterdog@aol.com with any ideas- thx a ton!  Paul  N0AH

Paul and Others:.:

I have a similar thing going on here, only the spacing is 30 KHz
apart. 1.818, 1.848, etc. It goes from 1.7 MHz to 2.3 MHz.
It is not very strong, but enough to make me ask why. The Magic MFJ-1025
box will take it completely away, but I use the 1025 to phase receive
antennas. I really want to solve this the old fashion way. Fix It!.

I have tracked it to the utility poles. I had the telephone Co. here and
they disconnected house's one by one...(I think), no fix.
Next it was the CATV Company's turn. Take the CATV amp off and it's
still there. The they  grounded the phone and CATV line at every pole,
which helped. We went from 12 poles down to 3 poles where you can hear
it now.
The Spectrum Analyzer shows it plain as day when hooked to the 75 ohm
CATV cable drop to my house. It appears to be riding on the outside
shield of the CATV line however.
A hand held scanner up on the pole shows the same sig strength on the
CATV and TeleCo lines.
The strength gets louder when you touch the ground drops anywhere at the
pole. So there is cross pollution going on and we cannot determine which
utility is allowing the noise to propagate.

The only thing I can think of is maybe a neighbor has a wireless phone
distribution system in their house which uses the frequencies below 1.8
MHz and this crap crawls up in frequency until it dies. The wireless
system may use a "constant carrier" type of distribution where  the
ground and or neutral of the power system in the house for distribution.
I think Radio Shack had some intercoms that use this method to send
things around the house. I will spend more time with the Spectrum
Analyzer this weekend.

I just purchased one of these wireless phone distribution systems for
experimenting here. I am sure they are all different, but I have got to
start somewhere. I thought someone from FRC or PVRC may of had this very
same problem. I am not sure.

I am going to get the TeleCo back out here Monday and watch the house by
house disconnects, as there are now only 4 houses that can be suspect.

I have been working on this noise for 3 months. I will not give up. It
is now me against the noise.

I just got the water system pump station that is 3/4 of a mile away with
electronic controlled variable speed drives quieted down. That took 1.5
years worth of working with them, but now it is perfect. You can even
drive by the pump station with your AM radio on and you would never know
what is inside the pump house.... The Magic MFJ-1025 box kept us from
disaster during the whole process. Thanks to W8JI for designing a
magnificent product and my favorite MFJ product. The 1025 is 100 percent
better than the 2 other noise reduction boxes that I have on the shelf.
It really works!

Speaking of which, If you have not tried the new MFJ front end filter
for the MFJ-259B Antenna Analyzer (My next favorite W8JI design) box so
that you can use the 259B for big (or small) antennas on 160 and 80, you
really should. My 3 element vertical yagi for 160 is 1.2 miles from a 1
KW omni AM broadcast station on 1.47 MHz. Every antenna analyzer I have
is useless on 160 and 80 because of this AM station. With the MFJ front
end filter (again designed by W8JI) there is NO problem. I was shocked
to see it work so well! Why doesn't MFJ use model designators like
MFJ-1234-JI so that we know Tom created it?

Noise makes the best topband antenna systems..... poor systems.....

If anyone has any experience with in house wireless telephone
distribution systems and these systems transmitting outside the house
(not cordless phones), I would love to hear from you!
Or is this problem a bad doorbell transformer???

Tim K3LR

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