[GreenKeys] Strange RTTY Signal on 29.684

[Bob Camp]

Hi

Well 78 = 13 x 2 x 3. Unless the payload is 13 bits long, that would  
suggest a setup of 13 six bit words per block. Good old five level  
code with the start or stop bit stripped out would be a pretty good  
guess for the payload.

82 baud at 6 bits would give you a character every 73 ms. That's not  
to far off from 100 baud 5 level / one stop bit after reformating.

All of which proves nothing at all.

Bob


On Jun 7, 2008, at 10:19 PM, Peter Gottlieb wrote:

> For someone who is very deep into certain aspects of these  
> incredible machines I am about to ask a few very basic questions.
>
> How is the frequency of the signal determined? Is it the mark or the  
> space? How can you tell on such a signal what is the mark or space?
> How did you determine there is a 78 bit autocorrelation?  What  
> software did you use?
> How about the baud rate?
>
> Over here in NY I find many similar types of signals and had been  
> told many times they are encrypted.  Indeed, they are not normal 5  
> or 8 level code as there seems no way to set up to receive without  
> framing errors.  Unfortunately, every time I find some real solid  
> signal it is one of these.  I would love to be able to copy, even if  
> I can't decode.
>
> Peter
>
>
> John Vendely wrote:
>> The FSK signal I mentioned in my earlier reply to Geoff's posting  
>> is still present, 24/7, from the direction of Cape Canaveral Air  
>> Force Station. Apparently a ground wave system, the signal is quite  
>> strong in that vicinity, and fairly weak 35 or so miles down the  
>> coast at my QTH.  The exact frequency is 29.824536 Mc, with 100  
>> shift, 82 baud.  The signal is not completely random, but shows a  
>> 78 bit autocorrelation.  Of course, it's not baudot RTTY in the  
>> sense we normally think of, and therefore probably not of burning  
>> interest to most of us on this list.  But it's a specialized,  
>> narrow-shift, low baud rate FSK signalling system of some interest,  
>> especially given the paucity of true RTTY on the air these days.  I  
>> have no idea of its purpose, but further statistical analysis might  
>> shed some light on this.  It would be interesting to know if  
>> Geoff's "mystery" FSK signal shows the same characteristics,  
>> indicating the system might be in widespread use, perhaps by the  
>> military, or NASA.  Whatever the case, it's an interesting choice  
>> of frequency, which probably also has some relationship to its  
>> purpose...
>>
>> 73,
>>
>> John K9WT
>>
>>
>> ----- Original Message ----- From: "Geoff Fors" <wb6nvh at mbay.net>
>> To: <greenkeys at mailman.qth.net>
>> Sent: Friday, June 06, 2008 1:53 AM
>> Subject: [GreenKeys] Strange RTTY Signal on 29.684
>>
>>
>>> Out here in central California we are picking up a Baudot RTTY  
>>> signal on
>>> 29.684 MHz which runs 24 hours a day, 7 days per week,  
>>> continuously.  It
>>> appears to be encrypted.  It's coming in on ground wave as the  
>>> signal is
>>> about the same strength, day or night.  I haven't taken a look at  
>>> the signal
>>> yet as far as speed, shift, etc..
>>>
>>> Anybody have a suggestion what this might be?  10 Meters is an  
>>> exclusive
>>> authorization, not a shared band, so it shouldn't be anything  
>>> commercial. I
>>> am guessing it's some sort of military use, although how much  
>>> Baudot gear
>>> would the military still be using these days?
>>>
>>> Geoff
>>> WB6NVH
>>>
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>>
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