The AM Forum

I've heard some weird noise on 40 the past week that I thought was RFI.
Today I was watching it on the HPSDR spectrum display. It looks like a very broad FM signal sometimes over 1 MHz wide. and as little as 100 khz wide.
This afternoon I watched it track across 40 a number of times then park right on 7.150 to 7.3 MHz. NBFM demodulation is not a tone but more a random noise. The width did not change tonight only the FM modulation on the display. I'm sure it is coming from the East. I listened on a Racal, without a spectrum display it sounds like a combination of ignition noise and rain static. It raised the noise floor about 20 dB. I was listening to an Italian station on 7.135 with the signal only a couple KHz above frequency with the noise floor back to normal. Tuning speed was random then it just parked itself between 7.15 and 7.3.   

Another URN :-X :-X

Not sure if it's the same, but a couple weeks ago, we had some odd noise here on the left coast, reminiscent of the russkie pecker.

Turns out China is doing more / new OTH radar stuffs...  A few people here up and down the coast that I ran across where DFing it, and it was in the vicinity of a OTH radar station on Google Earth....

Might it be the same / similiar?

--Shane
KD6VXI

Ever since I was first  licensed in 1959, I have occasionally heard what sounds like broadcast stations transmitting FM in different parts of the HF spectrum.  It is always very broadband and comes in highly distorted, but I can make out voice and music.  Never have been able to ID a station, but can tell by the sound that it's broadcast. It couldn't be my particular receiver or antenna, since I have heard it with a variety of receivers and antennas, at several different QTHs in widely separated parts of the country.

Don't know if the spur originates from AM or FM stations, nor any clue how the signal ends up on HF frequencies. A TV or FM receiver spur? I'm not sure if I have heard it since TV went digital.

A long time mystery, whatever it is.

ionospheric intermodulation

Its the Super C's with the big signal. I hear they sold 2000 of them now.

C

Could it be the noise jamming from Sudan area?  That frequency range is where people have been commenting on for the last year.   

Similar to this Frank?
this is OTH Radar.

I don't know if this applies here, but I've noticed before military operations start, the bands get loaded with all kinds of strange sounding traffic. I know many here commented on this back before the 1990 and 2003 Iraqi invasions.

With the saber rattling going on in N. Korea and its neighbors trying their best to keep tabs on it, it wouldn't surprise me if various systems were being set up / tested or pulled outa mothballs. With Iran in the same boat, there could be some stuff coming from that region too. 40M will easily support RF prop from the mideast in the early evening, though RF from Asia would be more limited to our sunset/sunrise  area cuz they are in broad daylight, or we are, afterwards. (At least on the east coast)

** They wouldn't DARE pull any mil action until after Xmas, right?   ;)

T

Add to that some of the shi'ite that just came out from WikiLeaks.  Turns out that many of nominally hostile (to the west) middle eastern countries are really more concerned about Iran than they are about Israel, and have been secretly rooting for the Israelis and encouraging the US to help Israel take out Iran's nuke facilities. Persians and Arabs never have had a great love for each other, despite their common religious culture. Remember, Iran and Iraq beat each other to a pulp for some 8 years, before the recent and current Gulf wars flared up.

It appears that maybe Ethiopia has curtailed their jamming activity.  The past few times I have listened after 0400Z, the gawd-awful hash has been absent.  The Eritreans are still on 7175, as well as the 7165 signal. 7175 was coming in entertainment quality last night, but no sign of jamming.

East Africa is 3 hours ahead of GMT, so after about 0500z to 0700z, depending on the time of year, signals from that part of the world will fade out because of daylight in the propagation path.

40m has been practically devoid of signals after about 0500z recently, except for occasional signals, which are sometimes strong.  Maybe the skip is too long for N. American signals, and everyone is in bed in Europe.

I need to try that spectrum plot but looking it on the spectrum display the amplitude is almost flat across the signal except for the last 5 KHz of width where there is a bit of ringing in the modulation amplitude. Usually EMI response would come to a peak and roll off on both sides when a lead lenagt is resonated by a low rep rate pulse.

Really need a broad FFT spectrum display to see the whole signal. Otherwise it just sounds like static.

gone tonight

Actually I believe that you can hear North Korea directly most mornings at my QTH.
I hear what has been said to be a North Korean broadcast station on 3912, usually about 5:00-6:30AM EST, really good reception now that the mornings stay dark. The signal is pretty strapping, in fact it often covers up other fellows in the net until the sun comes up and the band shortens.

See http://www.clandestineradio.com/intel/stationmon.php?id=98&stn=94

Try it some morning - 3912 Kc, Voice of the People from DPRK.

-Bruce

I listen and sometimes join in on some grey line ops around 7160 and there are always complaints from the SE Asia Hams about a Chinese radar wiping them out. Hams in that part of the world are bothered by many high power SWBC stations and only leaves them a small slice of 40 to play.
Nations are flexing their muscles for something. It just wouldn't be good for end of year business reports to start something now.
Fred

Watch the week of Jan 7-11 very closely...

OH Gawd help us!!
Is there ever any interest in 60M channels cawmawn??
Fred

IF it persists, the logical approach would be to set up a watch. Everyone interested in this thing would take a couple of minutes each day to listen for it and then log day and time as well as what other 40 meter stations are coming in. A recording/snapshot of the spectrum and or waterfall would help  to characterize it enough so that others would know what to look for. For one thing, it has to be determined if is a local source and perhaps unintentional, or foreign and deliberate jamming or OTH radar crap. If it drifts around and then settles down on one frequency, is it the same each time?

once characterized, then see if it is heard all over and then the what else is coming in? logging will help to identify the direction/region of the source. 

I think this is the waterfall for OTH

not OTH looked more like an FM signal. Wide with constant amplitude across the response. Modulation was not a tone

Even if the source is positively identified as coming from China, then what? They are arrogant and not exactly easily swayed by world-wide public opinion.  http://www.bestoftheblogs.com/Home/34519

I seriously doubt that 40m interference issues are going to trigger the public to boycott Wal o' ChinaMart any time soon.

On a more encouraging front, Ethiopia seems to have turned off the white-noise jammers they acquired from China.

I thought they got those from RM Italy or Davemade?


--Shane

I think Randy finally figured out how to make R.F.

back again today

To follow up on Frank's question:

Tonight I checked 7.0, 7.1, 7.2 and 7.3.  Yes there is a 2 S-unit increase  up the band in noise when listening NE. I do not see it with the dipole but with the Yagi stack it is very clear.  My guess it is simply SW BC accumulated crud that all these guys have layered and layered. Even a station 50kc away has crud  that is on freq since they are running 100kw ++ and all of them are adding in.  With the stack some are +60 over, while they are down 20-25db on the dipole. The hash seems to start around where the BC stns start, around 7.2-ish.
 
I just tried it beaming SW. That f-b is huge, like -40db to Eu. The noise is exactly the same from 7.0 to 7.3.   So that pretty well proves it is coming from the NE and may likely be BC summed hash.   Are they using that digital AM stuff now? If like WTIC, gawd help us.
 
Then again, Frank said the noise disappeared at times, so maybe we are talking about different things here. Or was propagation down?

T

Cool, Wait until you see it on the spectrum display. Yes sometimes it goes away and sometimes it sweeps. I have not listened to it on the loops yet but KAZ it comes up 10 to 15 dB over a broad spectrum and rolls off quickly at the edges like an FM signal.