[IRCA] North Korean MW Jamming

["Chris Kadlec" <beaglebass@xxxxxxxxxxxxxx>]

To follow up on my recent posting about South Korean jamming, here's some examples of what's going on north of the border, including an FM bonus clip. A radio acquaintance is operating a KiwiSDR node about 8 miles to the south of my Seoul location, but those 8 miles are just enough to lose the Pyongyang jammers that were typical within the city, so my recordings may actually be relatively rare and likely some of the only examples of North Korean jammers on many of these frequencies. They may exist here and there in the local Korean DX community (seemingly unlikely as well) but not in the international forum for sure, especially as bringing a radio into the DPRK as a tourist is quite highly discouraged by the government - though it has been allowed - as it aids in the spread of... well, foreign signals they obviously don't want people hearing in the case you (purposely) leave it behind.

I'm unaware of the power these jammers are running but a few are very high-powered. It's hard to know as they are naturally jamming local Seoul signals and other Korean skywave signals, so there is a fair bit of CCI sometimes and it's not as easy to null out AM signals that like to ride on top of one another unlike FM. If anyone has picked up these jammers on these frequencies across the Pacific, please let me know. On the other hand, you may be hearing these noises and not knowing the origins. Now you will.

All recordings are from the Seoul-Incheon metro area, which lies immediately on the North Korean border (north suburbs lie just a few miles from the border).

* * * * *

One of the more impressive jammers is the 75kHz-wide jammer on 711. It broadcasts from either the Haeju tower site or Anak tower site. The recording starts on 684 and goes up to 756 where 711 is the center of the jammer and the frequency it jams, 711 KBS 1 Radio Seoul at 500kw. The recording is taken on the coast 11 miles from the local tower site.

http://www.beaglebass.com/dx/external/Jammer_711_75kHz.MP3

The same jammer on 711 sounds different depending on the signal strength. The same is true for every jammer. They get highly distorted when under a signal or when weak, making it very difficult to tell the true pattern of the sound. Here are two examples of the 711 jammer which shows that:

When the jammer signal is heard strong enough, you can hear its true sound:

http://www.beaglebass.com/dx/external/Jammer_711_Strong.MP3

However, when the jammer is weaker and/or the local signal is too strong, it sounds more like a hum, disguising its full sound (which will also be heard with 1566 later):

http://www.beaglebass.com/dx/external/Jammer_711_Weak.MP3

This is the so-called "video game" jammer (my original observation of what it reminded me of, which Paul Walker also called the same thing in his own post later). This one is the KCBS flagship station, 819 in Pyongyang. I've recorded it instead on local 2850 to silence the annoying local jammer. This is the sign-off of KCBS and the sign-on of the jammer.

http://www.beaglebass.com/dx/external/Jammer_819.MP3

This is Pyongyang's jamming of 891 Busan, another KBS 1 Radio signal. They highly dislike KBS 1 Radio to the point where two signals are even jammed in downtown Kaesong (just outside the Seoul suburbs) on FM as well; hear that at the end of this posting. 891 Busan is from 194 miles away and 250kw, but is not strong at all in Seoul. It's hard to hear clearly to start with and this jammer is actually quite weak and not extremely common to hear as the others.

http://www.beaglebass.com/dx/external/Jammer_891.MP3

Here's the jammer on 900, which is moderately common. The main signal is MBC Seoul under 10 miles away.

http://www.beaglebass.com/dx/external/Jammer_900.MP3

This one is only able to be heard atop the buildings in downtown Seoul, never at ground level (Henan, China can be heard behind it often at ground-level instead). This is local 972 at 1,500kw, 40 miles away and aiming north right at me nonetheless. You can null it out atop the buildings to the point you can hear the Pyongyang jammer behind it.

http://www.beaglebass.com/dx/external/Jammer_972.MP3

Another example of a hard-to-hear jammer, this is the jammer of local 500kw 1134 south of Seoul, 21 miles away. It's almost certainly parallel to the 1467 and 1566 laser jammers and very likely from the Anak tower site. 1134, like many local stations, turns off for a few hours every night, and that's the only time the DPRK jammer can be heard, usually in the null of Tokyo.

http://www.beaglebass.com/dx/external/Jammer_1134.MP3

This jammer is on most of the day, as well as the off-air hours of 1143 Radio Free Korea, which only broadcasts for skywave. I've recorded it here during the actual broadcast of RFK instead of during the off-air hours when it blocks Jilin Story Radio, which at 10kw is always behind RFK. RFK's tower is 6 miles from my location and is a relatively poor signal to begin with, always with another station behind it.

http://www.beaglebass.com/dx/external/Jammer_1143.MP3

This is one jammer that is so strong that it's impossible to shake. I don't think I've ever been able to listen to 1467 (an unusually strong coastal 50kw Mokpo KBS 1 Radio 192 miles to the south) without this jammer in with it. During talk, it's always heard. Music, it still comes in. Usually the two signals are simultaneous and both equally as strong. This is a laser jammer //1566 and likely 1134 too.

http://www.beaglebass.com/dx/external/Jammer_1467_Laser.MP3

The 1566 frequency is a real mess in Seoul. FEBC Jeju comes in well if you aim right at it but this jammer always finds its way in there. Yanbian is equally as strong and destroys whatever is left of a listenable signal. This is an example of what a laser jammer sounds like when there is heavy interference on the signal. It's //1467 but took me about 6 months to make that connection. FEBC is religious. The DPRK outlaws religion and the station, though only 250kw and from a far distance, aims north for many hours, hence a jammer.

http://www.beaglebass.com/dx/external/Jammer_1566_Laser.MP3

I call this one the helicopter jammer as it sounds like a helicopter or else an off-balance washing machine on a drying cycle. The first clip is upon sign-off, which comes halfway through the clip. It's manually turned off a while after 1am, never at the same time. What it's jamming is just beyond me. There are two 1kw KBS 1 Radio stations in the far south that barely make it to Seoul. However, 1584 is a frequency of the Korean-language network in Harbin, China, though 1476 (Sound of the Great Northern Wildnerness) is far stronger with more stations. So that's a bit of a mystery, but the jammer can be heard even in the south of Korea and looks pretty interesting on the SDR.

http://www.beaglebass.com/dx/external/Jammer_1584_1.MP3

And here's the same jammer. Sometimes the pitch of the tone changes a tad week to week as revealed in my different recordings of it, but this one sounds like a helicopter about to crash. It starts low and goes higher before starting again. I heard this pattern only once though.

http://www.beaglebass.com/dx/external/Jammer_1584_2.MP3

And lastly, here's an example of a typical FM jammer, which exactly mirrors those used in Seoul (though Seoul's on 92.5 was expanded a few years ago to be much wider and more of an annoying pest). This is 90.3 Kaesong, which broadcasts from the big tower at the south end of the main downtown strip, recording from my long-time Kaesong AM/FM site on the river immediately on the border, close enough to watch the North Korean farmers in their field. The jammer blocks HLKA-SFM Yongmunsan, which runs parallel to the Seoul signal of KBS 1 Radio, the one North Korea isn't a fan of. That signal is 50 miles away while the jammer is 15 miles from my location. The second Kaesong FM jammer is 99.5 vs. HLKM-SFM, another mountaintop KBS 1 R signal near the border. Otherwise, all other Seoul stations are free for listening in Kaesong, though until recently, the city hosted many South Korean workers who commute to North Korea daily to work in the factories across the border, so it's nothing Kaesong residents are unfamiliar with.

http://www.beaglebass.com/dx/external/Jammer_90_3.MP3

-Chris Kadlec
 Seoul AM Listening Guide
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