Mystery JT65 signal


Andrew OBrien
 

Fron a ham on my WSJTX group.
Andy K3UK

<ha3pg@...>
7:14am

Hi everyone,



I struggle identifying a mysterious JT65 signal on the
30m band. I already asked this in other groups but no solution so far.

A few weeks ago I stumbled on a regular JT65 transmission on 10140.7kHz
transmitting every third minute. The message does not seem like coming
from ham, no callsigns but a cryptic string of characters, see this
short log excerpt:

20200408_1402 -21 -0.6  763 # KJIVVFULMOAI              .
20200408_1411 -21 -0.6  764 # KJIVMFULMQ00              .
20200408_1417 -21 -0.6  764 # KJIVMFULMQ05              .
20200408_1420 -23 -0.6  764 # KJIVKFULMQB0              .
20200408_1426 -19 -0.6  764 # KJIVDFULMR00              .
20200408_1429 -24 -0.6  764 # KJIVMFULMQAG              .
20200408_1505 -23 -0.6  765 # KJIVJFULMP00              .
20200408_1535 -21 -0.6  764 # KJIVJFULMP95              .
20200408_1541 -25 -0.6  764 # KJIVLFULMP00              .
20200408_1547 -22 -0.6  764 # KJIVKFULMP7F              .
20200408_1550 -26 -0.5  764 # KJIVQFULMO9H              .

This signal appears to be JT65, at least it can be decoded as one and
transmits every 3 minutes. Looks like a beacon or similar.

What we know so far, not in any particular order of importance:

- freq: 10140kHz +700Hz USB
- transmits 7/24 every third minute
- correct JT65 coding, can be decoded using WSJT-X or JTDX
- the message shows a pattern of

    KJIVxFULMxxx

where capitals are always the same while at places x varying

- carefully examining condx, appearing/disappearing of the sig,
coincidences to FT8 sigs shows probable location somewhere in AS Russia,
East EU, or maybe North EU, although at his stage needs further
listening, collecting of data and evaluation to narrow possible area

See a screenshot attached from yesterday evening. Yet a few wav files
can be downloaded as 9A5CW Patrick recorded two days ago:

https://drive.google.com/open?id=1-asTxJwq0nEhQJlCs0M6v6rYgjcqz9QC

I am curious to know if anyone else also noticed this transmission, has
additional details or willing to help me spotting the source.


Thank you, 73...  Sanyi, HA3PG


Graham
 

Any of the  compressed format  systems ,  will  'always  produce ''valid''  out put , when  subjected to a  repeating  ''noise'' 
pattern , where  pre formatted  messages are  encountered, it becomes  ever more  ' realistic' 

Much merriment , is had, when  opera  responds to a  repeating , 'noise pattern [ usually a  keying attribute of a  'beacon kit' excited  transmitter' ] and go's on  to  print , what is perceived as  false  detections , only applies to  136 band , where  s/n levels  to  -45 dB are encountered ,  hence very low  spurious signals ,  cause  'havoc'  , once lodged in the  call  list , then other stations ,  similar respond ... catch22

I suspect, this is a  repeating  beacon , but not  JT system ,  intruder more  like ?

73-Graham
g0nbd


Patrick Lindecker
 

Hello Andy,

 

If KVASD (soft decoder) is ON, extract it to OFF. This decoder is very sensitive but introduce false decodes. The standard “hard decoder” has not this problem (although a false decode is still possible but very rare).

 

73

Patrick

 

De : main@digitalradio.groups.io [mailto:main@digitalradio.groups.io] De la part de Andrew OBrien
Envoyé : vendredi 10 avril 2020 15:08
À : main@digitalradio.groups.io
Objet : [digital-mode-radio] Mystery JT65 signal

 

Fron a ham on my WSJTX group.
Andy K3UK

<ha3pg@...>

7:14am

Hi everyone,



I struggle identifying a mysterious JT65 signal on the
30m band. I already asked this in other groups but no solution so far.

A few weeks ago I stumbled on a regular JT65 transmission on 10140.7kHz
transmitting every third minute. The message does not seem like coming
from ham, no callsigns but a cryptic string of characters, see this
short log excerpt:

20200408_1402 -21 -0.6  763 # KJIVVFULMOAI              .
20200408_1411 -21 -0.6  764 # KJIVMFULMQ00              .
20200408_1417 -21 -0.6  764 # KJIVMFULMQ05              .
20200408_1420 -23 -0.6  764 # KJIVKFULMQB0              .
20200408_1426 -19 -0.6  764 # KJIVDFULMR00              .
20200408_1429 -24 -0.6  764 # KJIVMFULMQAG              .
20200408_1505 -23 -0.6  765 # KJIVJFULMP00              .
20200408_1535 -21 -0.6  764 # KJIVJFULMP95              .
20200408_1541 -25 -0.6  764 # KJIVLFULMP00              .
20200408_1547 -22 -0.6  764 # KJIVKFULMP7F              .
20200408_1550 -26 -0.5  764 # KJIVQFULMO9H              .

This signal appears to be JT65, at least it can be decoded as one and
transmits every 3 minutes. Looks like a beacon or similar.

What we know so far, not in any particular order of importance:

- freq: 10140kHz +700Hz USB
- transmits 7/24 every third minute
- correct JT65 coding, can be decoded using WSJT-X or JTDX
- the message shows a pattern of

    KJIVxFULMxxx

where capitals are always the same while at places x varying

- carefully examining condx, appearing/disappearing of the sig,
coincidences to FT8 sigs shows probable location somewhere in AS Russia,
East EU, or maybe North EU, although at his stage needs further
listening, collecting of data and evaluation to narrow possible area

See a screenshot attached from yesterday evening. Yet a few wav files
can be downloaded as 9A5CW Patrick recorded two days ago:

https://drive.google.com/open?id=1-asTxJwq0nEhQJlCs0M6v6rYgjcqz9QC

I am curious to know if anyone else also noticed this transmission, has
additional details or willing to help me spotting the source.


Thank you, 73...  Sanyi, HA3PG




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