Do you hear SWISHING interference on 75m??

[WBear2GCR]

Fred,

There's little doubt that they do not broadcast from the school, but they do run the project and use computer control
for the transmitters.

I think that the only people who will know very much about this will be the Director for the Center, and maybe the main
tech who handles the actual hardware, and then MAYBE NOT EVEN THEM.

This will go back to the manufacturer of the devices.

Also, there may or may not be any requirement for them to monitor for spurious emissions. Worse of all, right now the
interfering signal(s) appear to not be present, so a complaint to even the FCC will not show anything, unless A) it is apparent at another geographic location (why I asked about who hears it or has heard it), or B) returns so that I or
someone else hears it in-band.

                                  _-_-bear

[W3RSW]

The bip bip bip thing;  if you had an sdr, you'd see it's sweeping across your QSO, is digital, and will shortly hit the next guys' QSO as it sweeps.

[K2AEP]

Maybe It's the "Bawwston Buzzy" Reincarnated.

[AJ1G]

When I heard the mp3 audio, I have heard that sound before.  4-5 years ago when I first heard it, it was all over the bottom end of the shortwave band extending above 2 Mhz into the 7 Mhz range including some spots further up in the bands.  One evening coming home from work, I was listening to KSL (1160) which I can only pickup at night.  When I left the following morning, I still had the radio in the car tuned to KSL but nothing was heard.  I get about a 1/4 mile down the road and got past a newly built house with a full brickwall around it, I started hearing that same sound again.  Subsequent checking in the car, it was always in the same spot in front of that house, did not hear anymore before or after that house or anywhere else down the road.  I assumed it was some kind of security system they were using, a dirty one at that.  I live in the Mojave Desert and if it is CONAR, one would think you would not pick up such a signal in the daytime.  I did check this early afternoon at home and that signal is there, starting around 4.465 and extends, in spots, to nearly 4.900.  Fortunately for me, it isn't as bad as it was in the past.

I have heard a similar interference on the AM band localized to a specific house I pass by on the way to and from work.  I assume that is coming form a home security system, maybe an intrusion motion sensor?  Don't they work at ultrasonic frequencies, maybe what's showing up on the BCB is a harmonic of the ultrasonic source?

[W6WAC]

When I heard the mp3 audio, I have heard that sound before.  4-5 years ago when I first heard it, it was all over the bottom end of the shortwave band extending above 2 Mhz into the 7 Mhz range including some spots further up in the bands.  One evening coming home from work, I was listening to KSL (1160) which I can only pickup at night.  When I left the following morning, I still had the radio in the car tuned to KSL but nothing was heard.  I get about a 1/4 mile down the road and got past a newly built house with a full brickwall around it, I started hearing that same sound again.  Subsequent checking in the car, it was always in the same spot in front of that house, did not hear anymore before or after that house or anywhere else down the road.  I assumed it was some kind of security system they were using, a dirty one at that.  I live in the Mojave Desert and if it is CONAR, one would think you would not pick up such a signal in the daytime.  I did check this early afternoon at home and that signal is there, starting around 4.465 and extends, in spots, to nearly 4.900.  Fortunately for me, it isn't as bad as it was in the past.

I have heard a similar interference on the AM band localized to a specific house I pass by on the way to and from work.  I assume that is coming form a home security system, maybe an intrusion motion sensor?  Don't they work at ultrasonic frequencies, maybe what's showing up on the BCB is a harmonic of the ultrasonic source?

I will have to check again and compare, hadn't really done it in a few years as car radio been tuned primarily to FM.  On the other hand, I'm not that far from Edwards AFB, who knows what goes on out there (get your foil hats out).

[kd1nw]

the bip bip bip boston buzzie thing might be haystack observatory? looks like the have a digisonde
http://www.haystack.mit.edu/tech/iono/index.html

i hear it 24 / 7 here in S. RI from 160 on up to at least 10 mhz.. havent really checked how far up i can hear it. you can watch it sweep up with an sdr or set up a few receivers on 160, 80, 60, 40 and listen to it go from rx to rx in quadraphonic stereo.

The original post might be hearing codar.. there's tons of them in the 4-5 mhz range, I used to even hear one around 25 Mhz but havent listened in a while...

73 Kevin KD1NW

[WBear2GCR]

I am hearing a swish-swish that has peaks about 5KhZ wide spread along the band, that also do shift somewhat in center freq. In the 75m band. They seem to bear some resemblance in terms of the rate of "swish" to the known CODAR signals that are between 4.0 and 5.0 mHz. Beyond that I still have no idea if this is very nearby local, in the local area, or bombing in from some distance.

I was hoping that others might have heard the same swishy.

If no one else has heard it, the initial conclusion would place it very nearby local - although given that it starts off at sunrise at a low level and builds in intensity - WHEN IT IS PRESENT - tends to not support the very nearby local idea strongly. But strange things do happen.

It's not been strong lately, and was not present at all this morning or Saturday morning...

I heard some of it in the AM during the week, weakly on 160m.
It is present on my R-392 as well as my TS-440, so not likely an IF artifact.

                   _-_-

[PA0NVD]

In Europe we have a lot of interference from the converters of solar panels. Long wires, high powers, switchers at 25 kHz and running only at daytime.  They also give spurious every 25 kHz and very unstable paterns (probably due to the sunshine variations and power demand variations of the house)

[WBear2GCR]

Interesting.

Will have to give this some attention, and note if there is any correlation with the sunshine % or not.
I don't think there is, but it is worth considering. The 25kHz spacing part is about right, but the entire
spectrum of interference moves while the spacing between "bumps" of swish seems about constant.

                    _-_-

[PA0NVD]

The power converters are pulse width modulated with a fixed frequency, so indeed the distance between the interference frequencies remain constant, but the total spectrum will change. If it are converters from solar panels, the nice thing is that you can see the panels and listen close to the houses with panels.

[WB2EMS]

If no one else has heard it, the initial conclusion would place it very nearby local - although given that it starts off at sunrise at a low level and builds in intensity - WHEN IT IS PRESENT - tends to not support the very nearby local idea strongly. But strange things do happen.

I'm starting to hear odd bits of wideband interference around my area as well, during the day, but blessedly not in the evenings when I'm more likely to be on the air. I believe it may be from the proliferation of solar panels on the houses around the area. There is a very strong group of folks pushing solar power in our county, and at least 5 houses within a half mile have sprouted panels. From spending time on a friend's sailboat with solar charging I know his charging system was very noisy, making HF operation impossible during sunlight hours unless we shut the system down, which he was reluctant to do. I suspect that grid tied inverters may be spreading HF crap and coupling it into the power lines to boot. 

Whatever happened to part 15 compliance? Nowadays you can see on the boards where they made room for the RFI filters for the test articles, but in production they don't populate the parts to save $.03/unit.