[GreenKeys] Questions about some signals on the air.

[John Vendely]

Tony,

If it's 75 baud, 850 shift, it is likely to be NATO STANAG-4481, which 
is a 75 baud synchronous teleprinter system, virtually always with 
online encryption using the KG-84.  When "phasing", the KG-84 sends a 
sequence of mark/space reversals followed by a preamble which is easily 
recognizable, then pseudorandom data.

If it's 50 baud, 250 shift, it could be the Russian Navy system known 
colloquially as "36-50".  It's a specialized synchronous teleprinter 
code that runs 50 baud, 250 shift, and occasionally idles at 36 baud.  
It is virtually always encrypted, and frequently goes into "phasing" 
sequences consisting of 50% duty cycle mark/space reversals.  It's an 
old mode which is still in widespread use, with many ship and shore 
stations on many frequencies throughout the HF range.  It is not baudot 
code, of course, and cannot be copied on 50 baud baudot equipment.  I 
have decoders here which will decode it, and have monitored these 
stations on various occasions.  I've monitored 36-50 signals 
periodically over the years, but have heard only a very few cases in 
which they transmitted in the clear running test tapes, or with operator 
chat (op-chat) about circuit setup.

There's essentially nothing to copy from either of these systems...

73,


John K9WT

On 5/25/2012 11:30 PM, tony j. podrasky wrote:
> Hello Richard et al;
>
> I haven't listened (right now) but I am assuming it is a signal that:
>
> o runs 850 Hz shift
>
> o sounds like about 35-66 WPM - but has a "stutter" where some pulses
>     are slightly longer once and a while.
>
> o just before it drops carrier it goes into a 50% duty-cycle mark-space tone
>     toggle for about 5 seconds.
>
> o then drops the carrier.
>
> o then comes back on and does it again.
>
> --
>
> I have chased this signal, found the identical transmission (using dual
> receivers) on other frequencies. It is EXTREMELY strong where ever I
> find it. And I've examined the signal with all the tricks I have at
> my disposal and haven't been able to find rhyme nor reason of how
> it works.
>
> I had researched all over GOOGLE and can not find anyone who can
> give me any useful information about it.
>
> I'd pay up to ten kilobucks to be able to decode it - if the data
> was of any interest.
>
> It REALLY, REALLY bugs me that it is so strong and I can't decode it.
>
> UE,
> W6ESE - tony
> NNNN
> ZCZC
>
>
> Richard Knoppow wrote:
>>       I am using MMTTY and receiving on an R-388.  AT about
>> 10.430 I find a very strong RTTY signal which seems to be
>> there most of the time. I can't find any combination of
>> settings that decodes into anything but nonsense.  What is
>> this?  Is it encrypted and if not how do I go about
>> receiving it.  I've run into other non-ham signals that are
>> similar. Please forgive my ignorance.
>>
>>
>> --
>> Richard Knoppow