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HF/MW/LW General Discussion General discussion on monitoring the HF (High Frequency), MW (Medium Wave), and LW (Long Wave) spectrum (0.5 - 30 MHz)

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Old 10-09-2010, 2:17 AM
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Question Ticking QRM noise

The past few days I have been hearing a strange ticking noise (sounds like a clock!) on various frequencies (between 3-12MHz or so). It definitely sounds man made and also brings up the background levels on anything lower than 4 MHz. Guess I have my work cut out for me tomorrow to find out what could be the culprit. And before anyone asks, I was NOT tuned to WWV or WWVH
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Old 10-09-2010, 9:40 AM
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It may be an actual clock digital or analog...just a thought...or a timer of some sort?
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Old 10-09-2010, 12:14 PM
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Are you hearing it consistently between 3 and 12 MHz or just on certain frequencies in between? There are other time stations out there besides WWV and WWVH. Here is a list of some of them:

SW Time Signal Broadcasts
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Old 10-09-2010, 2:43 PM
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Wonder if the Russian Woodpecker (Russian Woodpecker - Wikipedia, the free encyclopedia) is back, but has slowed down a bit after so many years.
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Old 10-09-2010, 3:14 PM
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He's right, every one should be hearing it because I am too. It sounds similar to the old Russian Woodpecker but not as loud (the Russians did it right!). Some sort of over the horizon radar, but that's my best guess. No idea where it's from. I'll record it next time I hear it.
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Old 10-09-2010, 4:26 PM
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HEY maybe thats the ticking i have too damn woodpeckers on my coaxial again. Brandon try to record it so i can compare it to mine. The signal that is
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Old 10-09-2010, 5:09 PM
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Brandon, what was the mode and frequency in your recording?

It really does not sound like an OTHR of any kind, there simply is no swept sound to it and to only have 1 tick per sec (and these are exactly 1 tick per second) without a sweep would mean a very limited capability in any radar. Radars either tend to pulse more frequently if they are not sweeping, or they sweep during a wider PRI pulse.

T!

Last edited by Token; 10-09-2010 at 5:20 PM..
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Old 10-09-2010, 5:29 PM
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I think this is local interference because it shows up every 60 kHz or so.

Audio clip of noise
Screenshot from Winrad
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Old 10-09-2010, 5:33 PM
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Oh, I didn't see that you had a link to an audio clip (you gotta underline those or sumthin). No, that's not OTH Radar. Dunno what that is. Something local.
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Old 10-09-2010, 5:59 PM
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Wow i never heard anything like that before. I would rather have that as RFI than what i get
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Old 10-09-2010, 8:07 PM
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I got nothing here all the way through the spectrum-I guess it couldn't break my bubbleHOWEVER....I do get these similar blips in the military HF ranges such as 4-5khz 18-19khz and one or two around 24-26khz. If you listen to mine they are at 1 sec intervals and they have a "shoop" characteristic-if you listen closely to Brandon's I mean REAL close-there seems to be the same thing only way more abrupt. I call it to be radar. But wada I know
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Last edited by ridgescan; 10-09-2010 at 8:21 PM..
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Old 10-09-2010, 8:35 PM
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Quote:
It really does not sound like an OTHR of any kind, there simply is no swept sound to it and to only have 1 tick per sec
anyone nearby have an electric fence ?
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Old 10-09-2010, 9:30 PM
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I gave up trying to figure out the rfi/qrm for my setup. I just have to live with it
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Old 10-09-2010, 10:33 PM
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Quote:
Originally Posted by ridgescan View Post
I got nothing here all the way through the spectrum-I guess it couldn't break my bubbleHOWEVER....I do get these similar blips in the military HF ranges such as 4-5khz 18-19khz and one or two around 24-26khz. If you listen to mine they are at 1 sec intervals and they have a "shoop" characteristic-if you listen closely to Brandon's I mean REAL close-there seems to be the same thing only way more abrupt. I call it to be radar. But wada I know
I assume you mean 4-5 MHz, not kHz. Likewise the 18-19 and 24-26 range, MHz, not kHz.

The "shoop" sound you are describing is the frequency sweep of the radar. That is the important part that is missing from the sound clip Brandon posted, if you put it through spectrum analysis software, maybe like Spectrogram, you will see it is a simple pulse with no sweep.

As I said, a pulsed radar with a 1 second PRI and no sweep is going to be extremely limited in function, and a near complete waste of time and money. As far as I know there are no HF radar systems anywhere in the World that have a simple, unmodulated, pulse with a PRI that slow. There is NO advantage to such a system and a lot of wasted effort. Either shorter PRI's or FMCW or a combination of pulsed FMCW is the rule, other than that you are spending a lot of money and getting little return.

A simple pulse (this description does NOT apply to an FMCW or IFMCW swept radar pulse) with a PRI of 1 second would yield a maximum unambiguous range of just about 93,000 miles. But the longest path you can possibly have around the Earth is just under 25,000 miles, so you would be unable to tell where your return is actually coming from, is it on the first lap of Earth or did it skip over (and increase ambiguity) and not paint until the second? This indicates that there would never be a need for a PRI longer than about 0.27 seconds to get a return off of anything on the Earths surface or near atmosphere. Slower PRI's result in less average energy returned from any target, making it less likely to be detected, so a general rule in radar design is to always use the fastest PRI you can get away with that does not impact other design constraints. Also, you can not expect propagation to really yield round the World conditions most of the time, so you pick your freqs and PRI's appropriately. You would calculate the maximum usable range for a given frequency and use that to define the fastest PRI you can get away with, then NEVER exceed that number unless you want to reduce your detection range. You can slow down from that point, longer PRI's do have uses such as differing blind speeds, but doing so cost you returned energy from the target so you only slow down as little as you have to.

Your video example is something called CODAR, it is a specific type of short range ocean surface monitoring radar (and it is NOT military). CODAR has sweep rates that generally run from 5 per second to 0.66 per second, 1 to 2.5 per second is the most common range for CODAR.

Here is a list of CODARs I have received at my location, it is far from complete, these are just the ones I have bothered to measure parameters on. http://token_radio.home.mchsi.com/CO...f_10052009.HTM

T!

Last edited by Token; 10-09-2010 at 11:20 PM..
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Old 10-09-2010, 11:22 PM
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Once again I am sorry for my annoying dyslexia with khz/mhz. I get mad at myself for it too and thanks for the correction-I will get it one day anyways thanks for the interesting lesson on radar too. So what do you think he is hearing?
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Old 10-09-2010, 11:45 PM
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I don't know, but I thought talkpairs suggestion of an electric fence was pretty good. I personally think the pulses are too evenly spaced to be an electric fence, the 10 pulses I measured were all exactly 1000 milliseconds apart with no variation. But I have no better suggestion of what it might be.

T!
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Old 10-10-2010, 2:29 AM
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It (Brandon's) has the same 1-second pulse as WWV. Now, if you were in Colorado, we'd be on to something. But just for kicks, wait it out and see if there's a +/- 10 second pause once every minute cycle.

It's probably a local clock circuit of some sort. Move the radio around the house, with a short wire for an antenna, and see what happens.

Ridgescan: next time you hear it, tune through it and listen to how it sounds differently depending which way you are tuning. Like a doppler effect.
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Old 10-10-2010, 1:49 PM
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ridgescan, I have put up a video on my Youtube channel of the CODAR you are receiving in your video link.

This particular CODAR has a center frequency of 4435 kHz, an upper frequency of 4448, and a lower frequency of 4422 kHz, for a swept range of 26 kHz. It sweeps down (from the higher frequency to the lower frequency) one time per second.

It, like all CODARs (but not all HF radars), is both swept and pulsed, the frequency changes both during the on time of the pulse and the off time between them. The transmitted pulse width is 1000 microseconds and the pulse repetition interval is 1900 microseconds, meaning there is a 900 microsecond dead time between each pulse. It also means there are about 526 pulses per sweep.

Video link here: YouTube - CODAR radar, 4435 kHz cf, Ocotober 10, 2010, 1720 UTC

Since the subject of HF radars came up I may do a series of videos on the different radars one might run across on HF.

T!

Last edited by Token; 10-10-2010 at 3:03 PM..
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Old 10-10-2010, 3:51 PM
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Delete

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Old 10-10-2010, 6:46 PM
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Quote:
Originally Posted by Token View Post
ridgescan, I have put up a video on my Youtube channel of the CODAR you are receiving in your video link.

This particular CODAR has a center frequency of 4435 kHz, an upper frequency of 4448, and a lower frequency of 4422 kHz, for a swept range of 26 kHz. It sweeps down (from the higher frequency to the lower frequency) one time per second.

It, like all CODARs (but not all HF radars), is both swept and pulsed, the frequency changes both during the on time of the pulse and the off time between them. The transmitted pulse width is 1000 microseconds and the pulse repetition interval is 1900 microseconds, meaning there is a 900 microsecond dead time between each pulse. It also means there are about 526 pulses per sweep.

Video link here: YouTube - CODAR radar, 4435 kHz cf, Ocotober 10, 2010, 1720 UTC

Since the subject of HF radars came up I may do a series of videos on the different radars one might run across on HF.

T!
Yeah T please do your thing! Your stuff is fun to watch and good learning. In two of your posts I learned a ton about radar I never knew carry on!
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