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 K
aesong residents are unfamiliar with.
http://www.beaglebass.com/dx/external/Jammer_90_3.MP3
-Chris Kadlec
Seoul AM Listening Guide
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