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Author Topic: Wideband noise on 75M in the Northeast - Where from?  (Read 11904 times)
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KK4YY
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« on: December 09, 2018, 03:28:32 PM »

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


* 75M_noise.png (1360.14 KB, 1213x382 - viewed 317 times.)
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« Reply #1 on: December 09, 2018, 04:14:40 PM »

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

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
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Stephanie WX3K
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« Reply #2 on: December 09, 2018, 04:17:59 PM »

Don

Can you share how you accomplished a TDOA calculation ?


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
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Stephanie WX3K
Eico 720/722/730  HRO50T
"Thunder is good; Thunder is impressive but it is lightning that does the work" ...Mark Twain
KK4YY
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« Reply #3 on: December 09, 2018, 04:37:58 PM »

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
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K1JJ
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« Reply #4 on: December 09, 2018, 04:57:12 PM »

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


* K1JJ_ 75M loops at 190'.jpg (242.61 KB, 618x768 - viewed 233 times.)
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KK4YY
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« Reply #5 on: December 09, 2018, 05:13:29 PM »

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
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« Reply #6 on: December 09, 2018, 05:17:33 PM »

Awesome ! Very intriguing

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
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Stephanie WX3K
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« Reply #7 on: December 09, 2018, 05:54:23 PM »

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?
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« Reply #8 on: December 09, 2018, 06:08:39 PM »



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
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Lou W9LRS
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« Reply #9 on: December 09, 2018, 07:27:59 PM »

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/
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« Reply #10 on: December 09, 2018, 09:01:25 PM »

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.  Grin

Maybe I'll twiddle the receive loop around and see what bearing I get a null on.
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kb3ouk
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« Reply #11 on: December 09, 2018, 10:02:27 PM »

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

Oh great. No wonder it is strong here practically all day, I'm pretty much right in the middle of all 4 of those.
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N3HQB
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« Reply #12 on: December 09, 2018, 11:28:52 PM »

Not near Hagerstown, MD...

About S9 to 5 over tonight, but not local.
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« Reply #13 on: December 10, 2018, 12:42:24 AM »

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?
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Chris, AJ1G
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« Reply #14 on: December 10, 2018, 12:51:40 AM »

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.
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Chris, AJ1G
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« Reply #15 on: December 10, 2018, 08:11:42 AM »

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.
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KA2DZT
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« Reply #16 on: December 10, 2018, 10:39:02 AM »

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
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« Reply #17 on: December 10, 2018, 11:52:09 AM »

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.
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« Reply #18 on: December 10, 2018, 11:58:54 AM »

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

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« Reply #19 on: December 10, 2018, 12:14:08 PM »


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
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« Reply #20 on: December 10, 2018, 04:30:53 PM »

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.
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« Reply #21 on: December 10, 2018, 04:39:12 PM »

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.
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« Reply #22 on: December 10, 2018, 05:32:01 PM »

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. 
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« Reply #23 on: December 10, 2018, 07:02:49 PM »

Russia? ARRL swamp gas!   Grin  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
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Use an "AM Courtesy Filter" to limit transmit audio bandwidth  +-4.5 KHz, +-6.0 KHz or +-8.0 KHz when needed.  Easily done in DSP.

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« Reply #24 on: December 10, 2018, 07:48:36 PM »

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.
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