The 1053 jammers are complicated, as is that whole busy frequency - the busiest, by far, in Seoul. The main two are Seoul and Gimpo. The Seoul one is the one everyone always hears overseas, but it doesn't get out well locally. I'm not sure if it's directional, but I'm going to guess not. The tower site has 19 towers, whereas the Gimpo site is 4 large towers in a line, exactly similar to the site in Jeju-do. The 1053 siren jammer is on 16 1/2 hours a day with very clear on/off times. The Seoul jammer had been 24/7 for the longest time, but lately has been turning off. It turned off tonight at 11:19pm local (1419 UTC) leaving Shenyang and Yanbian to fight it out, but I'm hearing one of the new Hwaseong jammers in the distance, though not from there. A few jamming sites have gone online in the past two weeks across the country. I try to stick to Seoul, which my publication covers, and ignore the other areas or else I'd go insane.
The Gimpo jammer, while I have no absolute proof of it (they don't share this information, obviously) is aiming south. Why? The purpose of jammers isn't to defeat the signal they're up against. You don't aim *at* the signal you're jamming. AM radio - even FM - doesn't work like that. So aiming it northwest would be a futile effort against a 1,500kw powerhouse. 1053 Haeju clocks in at 75-80dBu at my DX site in Incheon, 61 miles from its tower. Clear water path does damage. There is no defeating that signal and it's a ridiculous attempt to hope to. So the point of the jammers is to cover the signal by any means necessary to the majority of the population. 50% of the nation's population - 26 of 51 million - live in the Seoul metro area. The aforementioned main Seoul site does a half-decent job at covering the most densely populated area. On the east side of the city, the Taereung experimental site fills in a few areas if necessary. The Hwaseong jammer site (which went full power on 11/21 after a year-plus of testing) is now taking care of the south and far south suburbs. The purpose of the Gimpo siren jammer is to cover Incheon. Incheon is a major city that is connected to and is part of the Seoul metro area and it's a coastal city. 1053 with that open water path really blasts into there and that jammer has a wider and louder signal that really is catered to the coastal areas. Gimpo is along the border, so if you want to cover the Korean population, the only way to aim is south (the other jammer is 16 miles to the east, so no reason to aim in the direction of Seoul, which is already covered). Furthermore, the tower site is just barely in Gimpo a short distance from the sea; basically it's right beside Incheon itself. And if I'm right, once upon a time, the site was *on* the sea. Incheon has been reclaiming land like mad over the years, so the coastline extends further and further out.
I'm not sure about 1566 and rebroadcasting audio. It may be another phenomenon, though things change year by year in the area. 1566 is a horrible frequency in Seoul. It's nearly impossible to get a clear signal on FEBC Jeju. There is a ridiculous amount of interference from Yanbian and the Pyongyang jammer (//1467 siren jammer which also decimates that frequency) really makes things muddy. Of course, I'll post that jammer with the rest of the North Korean ones soon. In 2015, I could get a very strong Jeju signal, but something changed by 2016; I think Pyongyang increased its power.
-Chris Kadlec Seoul AM Listening Guide
Date: Fri, 02 Dec 2016 00:03:04 +0000 From: Nick Hall-Patch <nhp@xxxxxxxx> To: Mailing list for the International Radio Club of America <irca@xxxxxxxxxxxxxxxx>, <irca@xxxxxxxxxxxxxxxx> Subject: Re: [IRCA] South Korean MW Jamming Message-ID: <6a5233e9b2078ad2306b3735bf254b20@mtlp000085> Content-Type: text/plain; charset="us-ascii"; format=flowed Thanks for doing this Chris. The subtleties are endless. Couple of questions. These are all originating in South Korea, is that correct? (except for video games on 819?) \\ further:This is the Gimpo siren jammer, THE most powerful jammer in Korea at 250kw, aimed south and on 16 1/2 hours a day, yet still stupidly leaving a full hour a day unjammed. While it's the most heard in the country, the dinky Seoul jammer 16 miles away is the one that gets out across the entire globe but can barely cover a 50-mile radius in Korea. We suspect its power is going up to the sky (or due north) as opposed to covering the ground as it should be.Gimpo being in South Korea, what is it jamming from the south? (which might be why we don't hear it on northerly paths?) This siren is what I heard on 1053 years ago, have a recording from 2007; the recordings from 2008 are without sirens. I don't think I've heard the sirens since then.This one is used at tourist sites along the DMZ. This is recorded less than 10 miles from the tower of 50kw 810 KCBS while standing beside the North Korean customs booth a half mile from the actual border, but a 60dBu silent signal very closeby is muffling it. These are mounted on little sticks on the side of buildings like 10-watt transmitters.I've heard something like this earlier this year on 1566. They're taking the audio of the originating station, distorting somehow and rebroadcasting? best wishes, Nick
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