The Seoul jammers aren't very strong at all and are meant only to cover the metro area, which is home to half the nation's population with the suburbs butting up against the border. 30 miles south of the city, those jammers are already rather weak and even in the metro area (and especially Incheon), North Korean signals can easily get through the jammers. I estimated that most of them are only about 50kw tops.
As for the signal that Paul posted, as I mentioned to him when he first posted, that video game sound is 819 Pyongyang, not a Seoul jammer. KCBS plays that during their off-air hours after 3:28am until 5:15 or so. The beehive jammers, as we've started calling them, change over time depending on which elements of the sound they are using at the time or if all the jammer-makers (for lack of a better term) are operating. There's the basic bee sound and then the the other sounds are added to that when everything is up and running and the modulation increased. This can be heard in my audio documentary. I've included the final 44 minutes of my 3-hour documentary here, which is the part that concentrates on jammers and propaganda (MW, FM, SW, TV, and numbers stations):
The part about components of the "beehive" jammer can be heard starting around the 9 minute mark. The full documentary (and the transcript of the propaganda segment) is at http://www.beaglebass.com/dx/seoul/ which has now been online for a year with 2,500 visits.
In addition, 801, depending on changes they are always making, has usually come from the Hwaseong transmitting site. That site was home to tests for the 657 jammer that were on/off for some time, as I had reported back then in May 2016. They were doing test loops for it at varying powers and on/off, 42 seconds off, 1 min 42 sec. on, repeat throughout the day. The tests you hear were recorded in suburban Ansan and were part of what eventually resulted in their final jammer pattern they rolled out 6 months later. Of course, I don't think that the on/off type of pattern you noticed could be attributed to this sort of thing, but it was still something that came to mind that I figured I'd share again out of boredom.
Date: Sun, 24 Dec 2017 16:46:07 -0800 (PST)
From: Gary DeBock <firstname.lastname@example.org>
To: "America, Mailing" <email@example.com>
Subject: [IRCA] 819 South Korean Jammer
Chris and All,
After reviewing some files from the recent Kona (Hawaii) DXpedition I was able to track down a recording of the Southern jammer attempting to compete with the monster 819-KCBS signal from Pyongyang. Even though the 819-Jammer may sound pretty strong in Seoul it definitely didn't bother KCBS very much in Kona.
The 819 jammer seems to be a continuous "Beehive" type signal similar to the old 1053 jammer. Because of the overwhelming strength of KCBS it only shows up during Pyongyang's fades, and even then it sounds pretty wimpy by comparison. This recording was made around 0853 on 12-18, and the jammer can be heard mixing with KCBS from 22 seconds to 40 seconds into the MP3 https://dreamcrafts.box.com/s/1ueov463q72ht02yq6zi5kcyidnwc4n9
By contrast the 801-Jammer seems to be an intermittent Beehive signal, coming and going at irregular intervals, and on a 50% on-off cycle when it does show up.
Gary DeBock (in Puyallup, WA, USA)