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Author Topic: Jamming?  (Read 1997 times)

Offline Captainenema

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Jamming?
« on: October 28, 2013, 1227 UTC »
I heard this rather unusual sound on my tecsun PL-660 here in the Hubei province of China. I asked on /r/shortwave on reddit and a poster seems to think it is jamming of some sort.

Any idea what it is?

http://yourlisten.com/Captainenema/rec002


Offline Echo_One

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Re: Jamming?
« Reply #1 on: October 28, 2013, 1231 UTC »
I heard this rather unusual sound on my tecsun PL-660 here in the Hubei province of China. I asked on /r/shortwave on reddit and a poster seems to think it is jamming of some sort.

Any idea what it is?

http://yourlisten.com/Captainenema/rec002



Sounds awfully like the Vietnamese Siren Jammer
Echo One - Bringing An English Eccentricity To The Air Waves

reportecho1@gmail.com

Offline Captainenema

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Re: Jamming?
« Reply #2 on: October 28, 2013, 1259 UTC »
Well that's interesting, will do some googling. Thank you for pointing me in the right direction.

Offline Echo_One

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Re: Jamming?
« Reply #3 on: October 28, 2013, 1308 UTC »
You are welcome
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Offline Token

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Re: Jamming?
« Reply #4 on: October 29, 2013, 2022 UTC »
I heard this rather unusual sound on my tecsun PL-660 here in the Hubei province of China. I asked on /r/shortwave on reddit and a poster seems to think it is jamming of some sort.

Any idea what it is?

http://yourlisten.com/Captainenema/rec002



I saw this signal at the same time, and it did look like the Vietnamese Siren Jammer in full DSB + carrier AM (I have seen this jammer use LSB, USB, USB+ carrier, and full DSB AM).  Although this jammer is often called “Vietnamese” this type of jammer is not only used by the Vietnamese, they are just the most common user of a “siren” type jammer.  Other countries have and do use similar jammers.

Normally you can tell what the target station is for any jammer, you may not be able to hear the target but often looking at a schedule and the frequency can tell you who the intended target is.  Knowing the station being jammed often helps firm up the ID of the source of the jamming.  In this case I noted the jammer in my log because it made no sense, it did not appear to be jamming anyone.

The frequency the jammer was on was not one a BC station was on at the time, and the jammer was probably off frequency (most BC station frequencies typically ending in 5 or 0 kHz, however this is not universal).  This off frequency situation is not uncommon for the Vietnamese jammers (they often set slightly off the intended victim’s frequency) supporting the possibility this particular siren was indeed Vietnamese.

More importantly, there were no scheduled transmissions on or near that frequency, and at that time, that were in Vietnamese or French, and aimed at Vietnam.  Later (1700 UTC) Radio France International would have been up on 13740 kHz, and may have been a target, but the jammer was on long before that programming started, I saw this jammer on freq before 1600 UTC.  Much earlier (ending at 1500 UTC) Radio Free Asia in Vietnamese was active on 13735 kHz.  This would be a very likely target for the jammer, but the jammer was so far off frequency it would not have been very affective, and it was still on over an hour and a half after the programming ended.

Speaking of time.  I see that you are new to the forum here, I have no idea if you are new to shortwave listening or not, but suspect you might be fairly new.  A couple of suggestions.

When you post something radio related to a forum (any forum, not just this one) by convention  you should include at least the frequency and date/time (in UTC) in the post.  In the case of what you posted the freq and local date/time are on the linked page but not in your post.  If the linked page goes down future searchers will have no idea of the date/time/freq of the signal we are discussing here.

Particularly true when talking about shortwave receptions, because they are often very wide ranging, when you do mention date and time (as in your linked audio) that date / time should be in UTC / GMT.  Almost all list/schedules/programing guides for SW are listed in UTC.  And, not everyone you ask / tell about a signal will know how to convert your local time to UTC/GMT.  In your linked page you gave the necessary data, local date and time, Hubei province, China.  But, the person who responded to you (Echo_One) is in a European time zone, and I am in the US Pacific Coast time zone.  I don’t know about Echo_One, but until I looked it up I had no idea that Hubei Province was in the GMT +08 time zone.  From that I had to convert to UTC so that I could compare it to my logs (to see if I had heard the same thing) and to published SW station schedules (to try and determine who a target station might be).

T!
T!
Mojave Desert, California USA

Offline Captainenema

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Re: Jamming?
« Reply #5 on: November 01, 2013, 0559 UTC »
Thanks for your thought provoking response, I will be sure to keep your suggestions in mind in the future. Quite the conundrum just as to what the Siren jammer was trying to jam.