Wierd RFI
 

On my Icom 756 spectrum scope I'm getting S9 peaks every 2kHz or so all
across the HF spectrum from 3mHz to 30mHz. This doesn't look at all like
QRN since it's regular and discrete and they're narrow signal peaks,
narrower even than a ham cw signal, all peaks the same strength. When I
switch to a vacant antenna position, or to my dummy load, there is nothing,
so I'm assuming it isn't coming over the AC line. The noise signal is
stronger on my vertical antenna than on my horizontal loop.

I've seen this before, intermittently -- one minute on, two min off, 20
seconds on, etc. But, today it's been going on for at least a couple of
hours.

Ideas anyone?

Thanks, Pete

"Pete Holden" wrote in message
news:zjTWb.290841$I06.2983429@attbi_s01...
On my Icom 756 spectrum scope I'm getting S9 peaks every 2kHz or so all
across the HF spectrum from 3mHz to 30mHz. This doesn't look at all like
QRN since it's regular and discrete and they're narrow signal peaks,
narrower even than a ham cw signal, all peaks the same strength. When I
switch to a vacant antenna position, or to my dummy load, there is
nothing,
so I'm assuming it isn't coming over the AC line. The noise signal is
stronger on my vertical antenna than on my horizontal loop.

I've seen this before, intermittently -- one minute on, two min off, 20
seconds on, etc. But, today it's been going on for at least a couple of
hours.

Ideas anyone?

Thanks, Pete



start turning things off to be sure it isn't in your house.

what does it sound like? you can tell a lot from the sound of the noise,
often more than a spectrum scope will tell you. is it raspy, buzzy, line
frequency modulated, narrow clean birdies? the quick cycling would sound
like a heater control, electric blanket, fish tank, something like that...
could it have become stuck? is someone boiling their fish tank? but the
2khz spacing would be more like a computer birdie from a keyboard or
monitor, but they usually aren't over such a wide range, and probably
wouldn't be intermittent like you had before.

Pete Holden wrote:
I've seen this before, intermittently -- one minute on, two min off, 20
seconds on, etc. But, today it's been going on for at least a couple of
hours.

It's probably some sort of controller like a thermostat or dimmer.
--
73, Cecil http://www.qsl.net/w5dxp



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I am assuming you are listening on SSB. Switch the radio to AM, and see if
it has a 60/120 Hz sound to it. I had something like that, 50 KHz all across
6m. Turned out to be a bad 60 amp main fuse.

Tam/WB2TT
"Pete Holden" wrote in message
news:zjTWb.290841$I06.2983429@attbi_s01...
On my Icom 756 spectrum scope I'm getting S9 peaks every 2kHz or so all
across the HF spectrum from 3mHz to 30mHz. This doesn't look at all like
QRN since it's regular and discrete and they're narrow signal peaks,
narrower even than a ham cw signal, all peaks the same strength. When I
switch to a vacant antenna position, or to my dummy load, there is
nothing,
so I'm assuming it isn't coming over the AC line. The noise signal is
stronger on my vertical antenna than on my horizontal loop.

I've seen this before, intermittently -- one minute on, two min off, 20
seconds on, etc. But, today it's been going on for at least a couple of
hours.

Ideas anyone?

Thanks, Pete

Well, thank you all for your ideas. I did check my dimmers and electric
blankets but found no RFI from them. It didn't seem to be anything from the
thermostat either. I do have a battery charger which maintains a lead acid
battery for my sump pump. I don't know about that yet. Of course, since
yesterday all has been quiet.

And, by way of full disclosure, I live within spitting distance of a massive
array of radar antennas associated with our Distant Early Warning system
that supplies input to NORAD in Cheyenne Mt. and who knows what sort of RF
they might be putting out occasionally?

Thanks again, Pete

oh... you may have been hearing the mother of all woodpeckers!

"Pete Holden" wrote in message
news:G%bXb.30491$uV3.52579@attbi_s51...
Well, thank you all for your ideas. I did check my dimmers and electric
blankets but found no RFI from them. It didn't seem to be anything from
the
thermostat either. I do have a battery charger which maintains a lead
acid
battery for my sump pump. I don't know about that yet. Of course, since
yesterday all has been quiet.

And, by way of full disclosure, I live within spitting distance of a
massive
array of radar antennas associated with our Distant Early Warning system
that supplies input to NORAD in Cheyenne Mt. and who knows what sort of
RF
they might be putting out occasionally?

Thanks again, Pete

I had a similar problem. It turned out to be the "ice-cube-tray-dumping"
motor in the ice maker in my freezer. I didn't find it until long after I
had had the power company come out and inspect their HV line, up about 40'
and their transformers. Naturally they didn't have any problems.
73 DE N6UF, Jim

"Pete Holden" wrote in message
news:zjTWb.290841$I06.2983429@attbi_s01...
: On my Icom 756 spectrum scope I'm getting S9 peaks every 2kHz or so all
: across the HF spectrum from 3mHz to 30mHz. This doesn't look at all like
: QRN since it's regular and discrete and they're narrow signal peaks,
: narrower even than a ham cw signal, all peaks the same strength. When I
: switch to a vacant antenna position, or to my dummy load, there is
nothing,
: so I'm assuming it isn't coming over the AC line. The noise signal is
: stronger on my vertical antenna than on my horizontal loop.
:
: I've seen this before, intermittently -- one minute on, two min off, 20
: seconds on, etc. But, today it's been going on for at least a couple of
: hours.
:
: Ideas anyone?
:
: Thanks, Pete
:
:

I had a similar problem. It turned out to be the "ice-cube-tray-dumping"
motor in the ice maker in my freezer. I didn't find it until long after I
had had the power company come out and inspect their HV line, up about 40'
and their transformers. Naturally they didn't have any problems.
73 DE N6UF, Jim


Oh brother! That makes me wonder about all the nearly "untold" devices and
gizmos I have around the house.

Thanks again, folks... I'm still looking -- or will be when it shows up
again.

Pete

While I can't guarantee it, from your description, it sounds suspiciously
like the OFDM version of BPL to me ...

Where are you geographically located?

Check out the videos at the ARRL site ... If I recall correctly, the last
test area on
the video is the OFDM system ...

Video showing results of ARRL testing in MD, VA, PA and NY
Internet: http://216.167.96.120/BPL_Trial-web.mpg - for those with broadband
access
Internet: http://216.167.96.120/BPL_Trial-small.mpg - for those with slower
access
Author: ARRL technical staff
I am cc'ing Ed Hare of ARRL on this - he may be able to shed additional
light on this and will probably want to correspond with you by e-mail.

It is VERY important that cases of BPL interference be determined
conclusively and well-documented - we can't afford to "cry wolf" at this
critical juncture.

73,

Carl - wk3c

"Pete Holden" wrote in message
news:zjTWb.290841$I06.2983429@attbi_s01...
On my Icom 756 spectrum scope I'm getting S9 peaks every 2kHz or so all
across the HF spectrum from 3mHz to 30mHz. This doesn't look at all like
QRN since it's regular and discrete and they're narrow signal peaks,
narrower even than a ham cw signal, all peaks the same strength. When I
switch to a vacant antenna position, or to my dummy load, there is
nothing,
so I'm assuming it isn't coming over the AC line. The noise signal is
stronger on my vertical antenna than on my horizontal loop.

I've seen this before, intermittently -- one minute on, two min off, 20
seconds on, etc. But, today it's been going on for at least a couple of
hours.

Ideas anyone?

Thanks, Pete

On 14-Feb-2004, "Pete Holden" wrote:

I had a similar problem. It turned out to be the "ice-cube-tray-dumping"
motor in the ice maker in my freezer. I didn't find it until long after I
had had the power company come out and inspect their HV line, up about 40'
and their transformers. Naturally they didn't have any problems.
73 DE N6UF, Jim


Oh brother! That makes me wonder about all the nearly "untold" devices and
gizmos I have around the house.

Thanks again, folks... I'm still looking -- or will be when it shows up
again.

Pete

I once had a flourescent light fixture in my garage which would intermittently generate an arc-like
noise in my AM radio. Sometimes the noise would start when the light was first turned on.
Sometimes it would appear after several hours. Changes of lamp tubes, ballasts, and grounding were
all to no effect. Several years later while I was changing the power cord in the light, I noticed a
small brown spot on a wire nut which was laying on the metal fixture. There was very little visible
damage to the plastic of the wire nut but after replacing it, the noise was gone. Apparently some
carbonization of the plastic was allowing an arc-through to ground, a case where lack of a ground on
the fixture might have eliminated the noise.

-ken-