The AM Forum

This signal popped up on 75M in the Northeast recently.

My attempts at TDoA direction finding places the source in the general vicinity of:
-State College, PA
-Harrisburg, PA
-Altoona, PA
-Hagerstown, MD

Any ideas or comments regarding this?

Don

I see the wideband noise on my 756ProIII scope. Its pretty much wiping out 3880. I take it this just started today.

Don

Can you share how you accomplished a TDOA calculation ?

Stephanie,

Here's a link that explains the process. It's too much to explain here. Plan to spend some time learning how to use it.
https://www.rtl-sdr.com/kiwisdr-tdoa-direction-finding-now-freely-available-for-public-use/

Don

Using old school phased array methods, it is definitely coming from W3-land likely in the area you suggested.  It is 20 DB louder to the southwest than NE from middle - CT.

T

Thanks, Tom.

I'm hoping someone local to that area can do some DFing groundwork and maybe pinpoint this darn thing. If we could know what kind of transmission it is, that may help.

Don

Awesome ! Very intriguing

Using my magnetic loop its definitely  to the South, MD / VA heading (from NJ. S9+20
Maybe a call to ARRL tomorrow can shed some light on it?

It would be nice if one could call up the Friendly CC monitoring station and have them take a look... Oh, I forgot.... never mind.

KLC

Maybe this is it>

https://www.eham.net/articles/145

Lou W9LRS

Hear it here on 3880 10 over with The France CW station mixed in.

Here's more:https://forums.qrz.com/index.php?threads/wide-band-mystery-noise-on-75.637954/

I remember folks with keyers synchronizing their dit rate to the old woodpecker and 'chasing' them out of the amateur frequencies. Makes a fella wonder what someone with a 'smug' radio recording and playing back a 20khz wide rendition of their signal would make their displays look like.  ;D

Maybe I'll twiddle the receive loop around and see what bearing I get a null on.

Oh great. No wonder it is strong here practically all day, I'm pretty much right in the middle of all 4 of those.

Not near Hagerstown, MD...

About S9 to 5 over tonight, but not local.

Just looked at the Kiwi Web SDR at Penn State in Happy Valley...it's audible there but not  with particularly high SNR.  Best SNR I've seen so far is on the WA1QIX SDR...signal strength is averaging about -80 dB, cyclic fading, at one point it strapped up to -72 dB for about a minute or two, looks like a deliberate increase vs. typical fading.  What's with that CW that occasionally fades into the audio?

That DFing technique using  KiWi Web SDRs looks pretty slick.  Now that the general source area has been localized, maybe we need to get a posse together and go on an old school 75 meter foxhunt.

I sent an e-mail to the ARRL last night with some screen shots. Lets see if they respond.
Last night it was barely audible in NJ, but on Steve's SDR it was quite strong.

I listen to it around 2AM on an SW receiver with a whip antenna and it was strong here in CNJ  Seems it was more up at 3900kc, not on 3875kc or 3885kc.

Fred

Checked it out y’day morning.
Same as a plasma TV signal but constructed to the upper part of 75.
I’ve Noted in detail, similar topic, on the QRZ. AM forum where I first came across the topic.
The screen shot on this forum looks much closer to what I observed on my Anan 200D.
The shot on qrz looks more periodic, not quite like a plasma TV.
https://forums.qrz.com/index.php?threads/wide-band-mystery-noise-on-75.637954/

So Almost identical but bandwidth restricted to trash from my house plasma TV.

May have been related to this little exercise:

http://www.thedrive.com/the-war-zone/25380/conga-lines-of-usaf-airlifters-filled-the-night-sky-across-u-s-for-joint-forcible-entry-drill

I have my doubts, but .... Just received this response from ARRL:

Hello Bob,
Yes, it appears to be over-the-horizon RADAR emanating from Russia.  It is centered around 3902 kHz and is about 75 kHz wide. It creates moderately strong interference in North America.  What we can do about it may be limited, since Russia is in ITU Region 1, which arguably, may allow such transmissions on that frequency.  We are looking into it.

Thank you.
Regards,

Bob Allison
WB1GCM
ARRL Assistant Laboratory Manager
Product Review Test Engineer

From SDR DF'ing, it appears to have come from State College, PA

It went off at 9:00 this morning.

I was on the air at the time - in a QSO, but listening at that very moment, and the noise went off very shortly (a minute maybe) after 9:00 this (Monday) morning.

Most likely there were phone messages, emails or perhaps even some personal notes waiting for whomever was in charge - and probably arrived at work at 9:00 or perhaps a few minutes earlier.

Anyway, it's gone and that's a good thing !!!!

Many many thanks for the folks who chased this down, located the source, called the FCC, etc. etc.

The Russia story seems unlikely. 75m propagation to that part of the world seems unlikely during daylight hours. Will we ever know? Might be interesting to search FCC records for the presumed location.

It would be interesting to know what caused this.  Had to be some serious power to generate such a signal over such a broad bandwidth, and antenna too.  Very curious. 

Russia? ARRL swamp gas!   ;D  Why blame Russia for everything that happens secretive?  Sounds like a cover-up when they say stuff like that.

I have worked Russia countless times on 75M and that signal was NOT from the NE of CT, rather coming from the Southwest using the directive array and likely no farther than 300 miles away after using vertical angle estimates.

Probably something experimental - and located right where the SDR and TDoA digital guys here said it was.

T

It was still pretty strong even after dark last night, and State College is only about 60-70 miles north of here. Whatever kind of ERP that thing was pumping out, it must've been making its own propagation.

Well, well...   chalk up some good detective work to the Radio Amateurs. Might be a suspect.


I just got this from Bob, WB2FOF - probably some new gov't contract:
http://micro.apitech.com/fac_statecollege.aspx

They gots plenty of cash-heat there:  
http://micro.apitech.com/amplifiers


Did an RF newbie set the mouse-freq in the middle of the ham band by mistake?  ;)

It would be fun if someone called them tmw to "inquire" ...
(888) 553-7531

T

While the 75M Doomsday signal seemed to stop suddenly around 9am yesterday (someone found a note on their desk to call the FCC asap), there are new reports of a similar noise in other areas of the country.

Coordinated cable modem attacks?

Certainly an opportunity to build TDoA skills!

Did a search last night in the FCC database, and a google search for "large antenna arrays" in that area. Nothing really stands out. For that much power, it's not going to be one small antenna - it would have to be some sort of "farm". The Russia info is bogus - I'm shocked that ARRL would say that, rather than say nothing. All who did their own DF'ing should send it to Newington to provide for data for continued research.

"Laura" said she wanted the hams to assist the FCC in matters of interference - we are waiting Laura!

I live one mile from that company in State College.  I was not listening at the time.  From the outside it does not appear to have any large antenna system.   Now I know about this I will do snooping around the place.  Every thing around here is not part of Penn State University.

I tend to think of something that would have a large antenna structure in that location and not associate it with a university. Don’t think anyone is doing that much research into HF over the horizon these days to begin with and with huge ready facilities up in Alaska why waste time in the middle of PA?
WMLK (9.275MHz) runs 25 or 50Kw in Bethel not that far from State college and there curtain antenna array and use of surplus and second hand equipment may be worth a look. Read on their web site that they had purchased a used BBC 250 Kw transmitter and recently installed that. It’s not harmonically related but who knows.
WINB (9.265MHz) is in Red Lion PA and think they are experimenting with some form of digital broadcasting on 7.325MHz this is from their web site:

A new DRM transmitter, an ASI CE-50000WS, was installed in April 2018 and is in program test at random times. The transmitter is rated at 15 kW and is using the Rhombic antenna at 062 degrees. The authorized schedule for this transmitter is: Monday-Friday 0700-0900 on 7325 kHz, 0900-1100 on 9265 kHz, 1100-1700 UTC on 15670 kHz.

Note that this is all pure speculation on my part and I have no first hand knowledge as to the quality of their engineering staffs or equipment but do have some years’ experience working with religious broadcasters and know that often there operations are often less than optimal. For that matter this can also be a AM broadcaster in the central PA region. Most AM broadcast properties are in questionable state of operations these days with FCC deregulation and budget cuts and a new generation of Broadcast engineers who are more centered on IT concerns then the operation of large directional AM patterns.
It’s not unknown for items to start to fail around the change of seasons and unless you actively check your pattern and do field readings you never know.

Anyone want to participate in a QRM Hunt Task Force? All that's needed to get started is the time, frequency, and location where the signal is heard. It's easier if it's picked up on a web based SDR so that others can hear it as well.

This map lists the location of SDRs that can be used for DFing https://sdr.hu/map (https://sdr.hu/map). Press your CTRL key and roll your mouse wheel for zooming in. Click & drag works for scrolling location.

These SDRs use this URL format so you can copy and paste receiver locations into your browser without having to retune each time: http://IP address:port/?f3900.00amz10

The example shows a preset frequency of 3900kc, the AM mode, and a zoom level of '10"

The next step is to check other receivers for the same signal then couple them together for approximate analysis using the TDoA function.

On 75M, all it takes is a dipole at 50' and a 15KW class C, D, E solid state (or tube) amplifier to put out a "local" wide signal like that.   Easily built and operated by even a ham. No big ant array needed. A big antenna array like the shortwave broadcash stations use is more suited for lower angle 3,000 miles trips (like radar) and would actually be weaker than a dipole within 300 miles.  I get the impression this signal was more piss weak out farther than 300 miles, based on reports.  In comparison, look how loud some of the biggest AM guns are on 75M when conditions are good. 60+ dB over S9...

We all know how clandestine and hidden a ham station can be on 75M. A 3.9 MHz signal like we heard could easily blend into the countryside.  It may not even be API, but whoever it is, don't expect a big antenna array on 75M.

My guess is that the tester either put the rig into a dipole instead of dummy load by mistake OR he figured the hams are so inept they would never know what hit them, and the safest place to run an illegal test was within the ham band... the playground of amateurs... :-)    Little do they know that the ham bands are probably policed better than the other shortwave bands. SDR and "Toad" technology has changed the game big time.

BTW, Clark - forming a DFing "jump team" is a great idea. Being organized with a group doing their own coordinated jobs to find the perp is unbeatable.  I will contribute my own input with array DFing. I can give you a heading and distance estimate in minutes on both 75 and 40M.


T

Could all this be the result of a converted Collins 21M and a case of beer?

Also around one mile from me are a few large DOD labs and contractors.   Most of what they do is not known by the public.

I also would be interested in the rest of the story, who, what, where and why.

Agree with you guys:
Also Pretty much what I mentioned as a possible pirate on an other board earlier; Here's what a local plasma TV looks like on 75 meters, 20db attn. of course since it's in my house.
It looks and sounds like what I heard on morning of Dec. 9th.  That signal ranged weakly from 3800 to 4000 with much stronger peak ranging around 3900 kHz.

The center peak can be simply shifted by changing TV channels.

Shifting phase/time in waterfall doesn't show up locally compared to kk4yy's picture.

So, Not exactly what was show earlier in kk4yy's shot but possibly similar and easy to generate.  

Edited again: Hey I think the link kkyyy provided for the kiwisdr direction finding is one
really neat dodad.!  Power to the People.  ;D  

THAT would be fantastic!

It would be great to have a group of amateurs in various parts of the country who have experience with directional antennas such as loops and phased arrays. Being able to contact them when issues such as this arise, gathering results, and sharing that info would be invaluable.

It would also be a lot easier to get a group like that together before, rather than during, a need.

I've been using the online SDR TDoA DFing for the last 4 months. A little practice with it goes a long way. Propagation characteristics enter into the accuracy, so when you use it matters too.

The State College Dfing I did at about 7:30-8:30AM (local) Sunday morning. The band was fairly stable and I didn't expect much propagation from Europe, as they were in full daylight at that time. I did get some erroneous results but discarded them as outliers. Many hits clustered around State College and Harrisburg very similar to the heat image posted by N1BCG. I was actually quite surprised that it worked so well given the weird nature of that signal.

I have, in the past, DFed some AMers making nice old buzzard transmissions to within a very few miles of their location of record. SSB ops tend toward a more rapid break-in operation that makes TDoA difficult.

Practice practice practice! ;)

Don