priyom.org

This morning has been busy for me, looking for new schedules of I_Df2 (Russian intelligence FSK - 200 bd, 1000 Hz shift) and I_Df3 (also Russian intelligence, 200 bd, 500 Hz shift), and also occasionally catching CIS-36-50 (M_Df1; 50 bd, 200 Hz shift (mostly) FSK used by CIS) and North Korean diplomatic FSK (D_Df1; 1200 bd FSK in bursts).

I_Df2 is an FSK system using online encryption, so decoding is impossible without having a key. It's sent in schedules starting at either full hour or half past hour that have 2 repeats, sent 10 minutes apart. Frequencies of repeats are always going lower. Majority of transmissions contain messages, but there are also nulls. Possibly related to family 1B [E07, G07, S07, V07, M12, XP family].

Here is what I found today (times are UTC, frequencies are centre and kilohertz):

* - did not look for this transmission;
** - found last week; conditions were so poor so I could not find 1120z sending;
*** - same frequency as Monday-Friday 1210z schedule in February;

I_Df2 sounds like this (with traffic):

Null message sounds like this:

I_Df3 is another FSK mode I am researching. It does not have as many schedules as I_Df2. It does not use online encryption, but ITA-2 with bit inversion instead. Messages are VERY rare and I haven't seen any other ID than 576. I also don't have any recordings of it sending a message. Behaviour of schedules is same as of I_Df2.

Null message for 576 decodes into:

)5761  00000""""""""""162

Which can be interpreted as:

)576 1 00000++++++++++162

I have no idea what is purpose of 162 present in every null. 1 indicates group count.

Here are known schedules of it (March; times are UTC, frequencies are centre and kilohertz):

* - not found in March yet; February frequencies: 12184/10169/unknown;
** - not found in March yet; February frequencies: 20862/18424/16346 (yes, they love high frequencies);
*** - found today;

It's very characteristic mode. Just listen to the sample to notice differences from other FSK's:

I occasionally look for CIS-36-50 which is FSK mode used by CIS. Ian Wraith, digital mode desk of ENIGMA 2000 is working on decoding of it for his digital mode programme called Rivet, so that's why I monitor it - simply to test it.

It's sent every 15-20 minutes, and one transmission may last up to 2 minutes. Here's full sample of one of them:

Today I also caught North Korean diplomatic FSK (1200 bd variant) for the first time. Sometimes it's very active and sent on up to 7 frequencies simultaneously. Mode is also unusual - LSB. You may wonder how I've got it that strongly in Poland, eh? That's due to their relay in Moscow that makes nice reception in Europe possible.

That is all for today from me, see you next time.

--danix111