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Author Topic: OTHR on 11m?  (Read 368 times)

Offline oar9fi

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OTHR on 11m?
« on: May 26, 2019, 1715 UTC »
The band was open this AM and was monitoring 27.385 and above it saw the distinct cris cross of a 10kHz wide OTHR. Not very strong but present looked similar to what I see just below 40m a lot.  I didn't get a screen shot but will try if I see it again.  -Justin in SW FL

Offline Josh

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Re: OTHR on 11m?
« Reply #1 on: May 27, 2019, 1628 UTC »
When I was into cb in the late 80s the band was filled with othr, othr with power levels over 9000. I imagine 10m is treated to the same. Old timers will tell you about the "woodpecker" a vile signal if there ever was one, that suddenly went qrt 26 April 1986.
The "woodpecker" was impressive enough to force HAM radio equipment makers to create noise blankers in their hf rigs designed to counter it specifically.
Conveniently located near Vincennes Indiana.

Offline R4002

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Re: OTHR on 11m?
« Reply #2 on: May 28, 2019, 1306 UTC »
I've heard OTHR on 11 meters several times before, sometimes even centered on 27.550 MHz (and naturally obliterating activity on the SSB freeband calling channel of 27.555 MHz USB).  Usually the OTHR is 20-40 kHz wide and the bursts only last for a few seconds before it moves up or down in frequency. 
U.S. East Coast, various HF/VHF/UHF radios/scanners/receivers

Offline oar9fi

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Re: OTHR on 11m?
« Reply #3 on: May 29, 2019, 1845 UTC »
Probably not as annoying on AM maybe thats why I never noticed it.  It was outside the US 11m band. I  know OTHRs are everywhere else on the HF bands. I just don't check 11m with an SDR  often but it was open. 73's   -Justin

Offline R4002

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Re: OTHR on 11m?
« Reply #4 on: May 30, 2019, 1417 UTC »
Indeed.  I've never heard it inside the legal 40 channel US FCC CB band 26960-27410 / 26965-27405.  Usually it pops up in the 27.5 MHz to 28 MHz region but sometimes its below channel 1 in the 26 MHz and 25 MHz bands.  I'm not sure if the OTHR systems in use in the USA have the 26.960 MHz to 27.410 MHz band as one of the "locked out" bands or I've just missed it when OTHR is actually in-band.  You're probably right about it not being as noticeable to AM operators vs. SSB.  Strong OTHR can obliterate SSB voice on 11 meters.  Not fun when you're trying to shoot skip on 27.555 USB :D
U.S. East Coast, various HF/VHF/UHF radios/scanners/receivers

Offline Leonard

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Re: OTHR on 11m?
« Reply #5 on: May 30, 2019, 1457 UTC »
Hello, new to the forum. I have a mobile radio and listen in my area for any activity and there is hardly any. So I set the radio at 27.385 and drive. But one sound I hear all the time and I have heard it a decade back, I am wondering if its the othr made mention in the previous posts. The sound I hear so often, its random but its strong. Imagine a cartoon coiled snake and the sound spins low and goes up, almost a watery sound, I'd love to know what that sound is. I have a link that is similiar, but my sound starts low and goes up, the link would put it in the same family of sounds.
https://www.youtube.com/watch?v=zFvDA5_msnM

Offline Josh

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Re: OTHR on 11m?
« Reply #6 on: May 30, 2019, 1710 UTC »
I want to say those are caused by ism equipment, and are not just inhabitants of the 10 and 11m bands. Another theory is they're ionosondes.

https://celectronics.com/training/learning/product_family_standard/ISM-Industrial-Scientific-Medical-equipment.html
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Offline Leonard

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Re: OTHR on 11m?
« Reply #7 on: May 30, 2019, 1813 UTC »
Thanks for the info, I lean toward it being the ionosondes. I can't tell you how many times I have the radio on just blowing static and here comes that bubble up sound. Its strong and I just  wonder who or what made that sound, from what I can tell it seems to come up on 10 meters,

Offline R4002

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Re: OTHR on 11m?
« Reply #8 on: May 31, 2019, 1301 UTC »
Josh makes a good point about the possibility of ISM QRM on 11 meters.  The ISM band is centered on 27120 kHz / 27.120 MHz +/- 163 kHz (so 26957 - 27283 / 26.957 MHz to 27.283 MHz), which conveniently covers CB channels 1-28.  I have heard what I presumed to be ionosondes on 11m freqs as well, but also the OTHR buzz buzz buzz (or wubbb wubbb wubbb) sounds. 

https://www.youtube.com/watch?v=9qfA4FZX3IA

^signal recorded on 27.555 MHz back in March 2014.  Note the bandwidth
U.S. East Coast, various HF/VHF/UHF radios/scanners/receivers

Offline Josh

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Re: OTHR on 11m?
« Reply #9 on: May 31, 2019, 1731 UTC »
Oh yeah, the wet fart radar mode is really wide.
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