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Author Topic: noise on 17m/10m  (Read 2432 times)
N9XM
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Posts: 14




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« on: January 26, 2005, 09:18:49 AM »

Hello everyone, I have been trying to locate the source of this noise for a awhile and thought I'd throw the question out there to see what recommendations I might get. The noise is a rythmic tic-tic-tic and I count about 68 beats a minute. Noticable on 17 and 10 the most but you can pick it out on 12 as well. No noise with the antenna disconnected. Tryed all the breakers in the house with no luck. I tried a portable AM radio in the shack but could not detect it.Shack is in the basement with a good ground. Antenna is a W9INN multiband up about 35 feet. I plan on trying the AM radio outside to see if that makes a difference. Anyone have a similar expierience? All comments welcome here and thanks ahead! Chris
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WB2WIK
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Posts: 21749




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« Reply #1 on: January 26, 2005, 02:57:05 PM »

What happens if you disconnect your antenna, short the feedline (if it's coax, just use a clip lead to short the center pin and shell of the connector for a moment) and then plug it back into the receiver?  Is the noise still the same after that?

WB2WIK/6
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N9XM
Member

Posts: 14




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« Reply #2 on: January 27, 2005, 08:56:39 AM »

WB2WIK/6,  The center of the dipole is up on the 2 story roof supported at the top of a 10 foot tower,I can't really climb up safely with the snow and ice. It [roof] has a 12-12 pitch which is about a 45 degree angle.It is not one that is fun to climb even when dry,you have to stick to the valleys and peaks like glue.I will try it if we get some warm days to thaw it.  Thanks, Chris
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KA0GKT
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Posts: 555




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« Reply #3 on: February 02, 2005, 09:21:38 AM »

I think WB2WIK meant the transmitter end of the feed line.

I can remember hooking a NE-2 indicator into a PL-259 and placing it on the end of the coaxial feed from a home-brew 15-M Discone I built on the roof of my father's shop building.  When it was raining or snowing, the little NE-2 would flash.  During a lightning storm, the Cushcraft lighting arrestor would sing as the static discharged across its spark gap.  I remember a winter wind storm (an Alberta Clipper) when the wind static would jump from the center pin of the PL-259 to the shell.  In a light rain, it would just go tick-tick-tick.

73

DE KA0GKT/7
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WB6BYU
Member

Posts: 16899




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« Reply #4 on: February 02, 2005, 12:59:53 PM »

Another way to implement Steve's suggestion: put a coax
"T" connector in the main feedline in the shack somewhere.
Use two of the ports for the main coax cable, and connect
a 1K to 10K resistor across the third port.  Do you still
hear the ticking?

If that fixes it, then the problem probably is static
build-up on the antenna.  It increses until something
arcs over (the noise you hear) which reduces the voltage
and it builds up again.  This often causes a repeating
noise, the rate of which depends on the amount of static
electricty being picked up by the antenna.

Otherwise, you can wind a 3-turn coil about 6" in diameter
on a wood frame and tune it with a 50pf trimmer cap.  
Add a coupling loop about half the diameter of the main
loop connected to some coax, and you have a quick DF
loop that can help you track down the source.

Some day I'll finish taking measurements and plotting
graphs and publish more of an article on simple DF loops.
They really aren't hard to build, and save a lot of
guesswork about the source of noise problems.
But, for now, if that isn't clear enough I'll be glad
to straighten it out by email.
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WD8DKB
Member

Posts: 271




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« Reply #5 on: February 04, 2005, 02:03:48 PM »

This is a bit strange but I get the same noise at my qth here in Ohio. 17 and 15 as well. It sounds like ignition noise with the rat tat tat . My noise blanker won't kill it at all. I have several wire antennas and receive the noise on all of them. I'll have to try the suggested tests. It lasts for hours at a time so can't be ignition noise. Sometimes 2 of our cable tv channels have buckshot shooting across the screen at the same time. Royal pain.  Good luck to both of us. Max
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K7PEH
Member

Posts: 1141




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« Reply #6 on: February 13, 2005, 10:16:36 AM »

Same noise is at qth in Kirkland Washington.

So, is this really the same noise.  The 68 beats per minute sound about right.  Also, I have an icom with a spectrum scope and I can see these on the scope but they may be noise generated peaks on the scope because they do not seem logical.  I mean, I don't think the spikes I see appear and disappear are the actual signal of the noise since I think the noise is very broad spectrum stuff.
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KA5S
Member

Posts: 229




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« Reply #7 on: February 19, 2005, 07:51:12 PM »

Have you or your neighbors got a new electric blanket or heating pad? I seem to recall hearing about a swept frequency interference like this from some of them.

If so, see http://hraunfoss.fcc.gov/edocs_public/attachmatch/DA-04-3253A1.doc

Cortland
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KA5S
Member

Posts: 229




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« Reply #8 on: February 19, 2005, 07:56:07 PM »

I posted the wrong URL. Here's the one that refers to this noise:

http://www.bext.com/_CGC/2004/cgc613.htm

excerpt

THE LATEST SOURCE OF RFI - AN ELECTRIC MATTRESS PAD
...inadequately shielded switching-type AC-to-DC power supply that's used to power the pad.
  RFI bursts are pumped out of the power supply in question even during the day when the pad itself is shut off.  It turns out that the power supply is constantly energized, and the AC power lines are inadvertently used as a giant antenna.  The interference sounds like "tic-tic-tic....," brief wideband RFI pulses with about a one second delay between pulses.  Interference extends at least 250 feet under the right conditions.
  The pad and power supply, manufactured by Perfect FitIndustries, is not FCC Part 15 compliant:  There was no Part 15 sticker on the system inspected by Communications General Corporation ("CGC"), and both Perfect Fit and the power ...

Cortland
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