The AM Forum

I've been hearing a strange interfering signal up and down the band. It seems to have a primary frequency up around
4.8xx mHz or maybe 4.4xx mHz. It appears at intervals of about 20kHz or so on the 75m band. In band I hear it on AM as what I would describe as the sound of a top loader washing machine, but "digital" in tone, going back and forth so to speak. It seems to move in freq. It generally goes away at sundown (approximately) and returns early in the AM, past dawn. I seem to recall having heard it at night over the summer.

In QSO today, W1TAV said he hears this out in Mass, near Boston.
I do not recall noticing it from my main QTH which is south of Albany by about 25 miles!
In addition this thing is easy S9+ most of the time.

IS ANYONE ELSE HEARING THIS SWISHY BACK AND FORTH SIGNAL??
If so, where are you, when do you hear it, and what strength?

I'd really like to get to the bottom of this one.

                          _-_-

Bear

Were you wearing your foil hat when this was happening?  I'm sorry, I could resist that.  I'll keep my panadapter looking.

Again, Sorry, I couldn't resist, Al

Thanks much Al!

No, this is serious interference, appearing at fairly close intervals across most of the band, and typically
about 5-6kc wide.

If you DO NOT hear it ever, that is good information as well.

Also check up above 4.0mHz for evidence of it.

                   _-_-bear

Hi Bear, I have heard the swishing on every band but 160m, 15m, and 10m.

Someone suggested it might be some spread spectrum el junko.


 

What's ur QTH?

Also what time of day on 75m?? And do you hear it parked (more or less) in the AM window??

I do, every morning. Gets appreciably stronger by 10AM right now.

               _-_-

                       

My QTH is East Central Iowa.

I have heard it most prominately on 75, 40, and 20, mostly during the evening.

On 75m mostly in AM window between sunset and 11:00 PM.

Phil - AC0OB

There is no excuse for annoying a cat in that way.

I know, Bear.  I was in a loopy mood.  I will keep an eye out.  I have head of the washing machine swoosh sound.  I will let you know if I see anything - even to the point of recording the waterfall snapshot

al

Can you post a brief recording of what you are hearing?

Did some "swishing" fishing:

Recorded 4.476 MHz

Is this the approx. sound and interval?


https://dl.dropboxusercontent.com/u/17340243/Swish.mp3

These signals just posted as an mp3 up around 4.5+ MHz are CODAR. There's a good writeup about it on Wikipedia, as I recall. Or write to Marty, N2IRJ at N2IRJ@arrl.net -- Marty's been studying these signals for a while.

73,

Kevin, WB4AIO.

whew !! thats a relief !! I was afraid it was Vega calling long distance .... hmmmm did you count the number of swishes between the silent parts ....didn't just happen to be a prime number, did it?

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.

How about a radar signal for a gate opener?   Or,  for those only activated by a button / remote,  a radar for ensuring cars aren't into the gates proximity or to auto open on exit.....?

Just a thought.

--Shane
KD6VXI

I believe Kevin, WB4AIO is on the mark on this one.. YouTube searches of "Codar signals" produces results just like this one, which fits exactly the signature seen and heard here.

https://www.youtube.com/watch?v=kwvSWDjRmbU

Question is if this fits Bear's query!

Jeff W2NBC

Much more tonal than what I hear now. BUT approximately the same period for the go/no go part.

What I hear is pretty much a sort of phasey white noise, as I said reminiscent of an old top loader washer going
back and forth, back and forth. Up in the middle of the 4mHz range it is louder and last time I listened somewhat
different in sound.

Regardless, IF it interferes with amateur service it is interference - unless, of course it is the friggin' government doing it.

But the really strange part is that I have not heard it at my main QTH, just up here in smAlbany (so far).
Next week maybe I will take time to listen up in the >4mHz area and see if it is parked up there...

Pizzzez me orf though, as it is LOUD.

BINGO!! Very much like this, but with sites along the band about every 25khz.
AND, I'd guess more like 4kW if in Moriches, or 40kW if farther away...

well if it is for the alleged purpose on utoobe, then it IS interfering.
perhaps a group signed letter to the FCC might be in order??

Lets keep looking into this, I'd say.

If it's CODAR that's being heard in the 75 meter band, then there must be a transmitter malfunction or operator error going on, and it probably will be resolved eventually. I have heard the Navy RTTY station NAM (normally centered on 4005 kHz) producing spurs within 75 meters more than once.

Also, there is a "clicking" sound often heard on the very high end of 75, around 3995 kHz, that seems to be exactly synchronized with the CODAR one second sweeps up around 4500 -- but I am not sure if there is any connection.

73,

Kevin, WB4AIO.

Perhaps it would be prudent to contact "them"?

How?

This is interesting. Ted K1QAR found this:

http://codar.com/ (http://codar.com/)

Worthy of discussion - apparently they can link via GPS multiple Codar sites... it's in the "inventions"
section.

Ok, the stuff we are hearing does NOT conform to their spec for power or frequency range of operation.
According to their product brochure. Not this company anyhow, unless it is a new and experimental installation.

However, Rutgers University...

Spot on the 4.5mhz observed signals!

http://marine.rutgers.edu/cool/maracoos/codar/radials/ (http://marine.rutgers.edu/cool/maracoos/codar/radials/)

Deeper and wider.

Now looks like a distributed source, perhaps synchronized and phased. Perhaps.
Which may explain the odd propagation that shows up inland in only some areas and not others.

Linked from a search on the Rutgers U ocean research site:

http://maracoos.org/content/maracoos-collaboration-exploring-new-realms-hf-radar (http://maracoos.org/content/maracoos-collaboration-exploring-new-realms-hf-radar)

Bear,

I'm about 3-4 miles from the Rutgers University Ocean Research building.  My daughter took some classes in that building last year.  I don't think they do any transmitting from that location,  but I may be able to dig up some more info about their research project.

Fred

Now that we have an interference thread going, how about the 'bip-bip-bip-bip' (lasts about a second) that is heard on 75-80 m?
 radar?
 carrier current communications on power lines?
 beings from beyond?
 inquiring minds need to know.
 73

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

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.

Maybe It's the "Bawwston Buzzy" Reincarnated.

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).

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

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.

                   _-_-

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)

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.

                    _-_-

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.

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.  >:(