OTH Radar?

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  • Updated 5 years ago

Woke up this AM to find a buzz-saw occupying 7140-7240 kHz. That bandwidth tells me that the pulses are approximately 20 microsec wide, with a rep rate of just about exactly 50 Hz -- pulses show 20 msec separation and sidebands show lines about 50 Hz apart.

If you work out the round-trip propagation time for 20 msec pulse spacing it comes out to around 3,000 km. But that is only 1,800 mi -- hardly what I'd call OTH -- like from Russia to here.

Anybody have any idea what this really is?

73 de Dave, N7AIG

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N7AIG

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Posted 5 years ago

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Dan -- KC4GO

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@Dave
What time and where are you located? I was up at 07:00 EST on 7.191 RV Service net been there to current didn't see what your talking about 
Antenna Mag Loop North and South, Vertical and a long wire tuned with SGC tuner.

Dan
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N7AIG

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Hi Dan,

I started watching around 0500 MST, or 1200 Z. Located in Tucson, AZ. When I last looked, around 1300 Z it was still running. Really strong here, at least S9 at times.

What puzzles me is why anyone would use a long propagating frequency like 7200 kHz at gray line time, when they can only discern objects within 3,000 km? I would have expected OTH Radar to have a much longer reach.

Dave
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Dan -- KC4GO

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Your MST of 05:00 is my EST 07:00 so we were on here... No sign of the signal you speak of on the east coast (Florida) maybe you will be lucky and find a few more who were on 40 about that time in other areas. Lots of things change with the Gray line on 40...
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KY6LA - Howard, Elmer

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I saw something similar on 40 about 0300 Pacific. Usually they are on 20M.
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Walt

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nice -83 dbm signal in seattle tonight - 0800z - since HF is used for everything from radar to spread-spectrum high speed data, it could be anything and I would not even guess.    Here, it looks like two carriers - one from 7140 - 7190 and 7210 - 7240.  Nice thing about global radio propagation, if someone transmits with lots or power, then lots of people are going to hear it.

time for sleep . .
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k3Tim

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Sleep is over rated!

GN 
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KY6LA - Howard, Elmer

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Post some screen shots
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k3Tim

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Big Sig into So CA.
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KY6LA - Howard, Elmer

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I am seeing the exact same waveform on 40.
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k3Tim

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This criminal intruder totally wipes out 40 meter SSB.
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Keith Wolford

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I'm "seeing" it this morning near Dallas, Texas.  Also heard in my mobile on my way in the work on Friday, 5/1 at ~5:15AM CDT.

Keith - AE5XN