[time-nuts] GPS System Message (was: TV Signals as a frequency reference)

Brooke Clarke brooke at pacific.net
Sat Mar 31 21:39:02 UTC 2018


Hi Mark:

I don't think the SV Messages are related to Over The Air Rekeying (OTAR) since they don't have enough characters.  My 
guess is that they are a modern form of the Emergency Action Message (EAM).
Here's a screen shot of a DAGR GPS receiver showing the first couple of messages as of 2 pm pacific time 3/31/2018:
http://www.prc68.com/I/DAGR.shtml#SV_Messages
https://en.wikipedia.org/wiki/Over_the_Air_Rekeying
https://en.wikipedia.org/wiki/Emergency_Action_Message

-- 
Have Fun,

Brooke Clarke
http://www.PRC68.com
http://www.end2partygovernment.com/2012Issues.html

-------- Original Message --------
> Or on the GPS/GNSS signals...  I was verifying Lady Heather's support for the old SV6/Palisade/Acutime receivers and came across a mention of the "GPS System Message" command.   It is requested by TSIP packet 0x28 and returns packet 0x48.  Newer Trimble receivers (like the Resolution-T don't seem to support the 0x28/0x48 messages. It is only mentioned in the SV6 docs.  The system message is a 22 character ASCII string embedded in the GPS navigation messages.
>
> If you dig into the GPS ICD docs it says it is used like a "bulletin board" for GPS users and can be a plaintext or encrypted message.  They currently seem to be encrypted...  perhaps a way to distribute P-code keys?
>
> I wonder if any of the newer GNSS sats have some hidden goodies in the signals?
>
> When sent to the SV6, you get a single response.  When sent to a Thunderbolt, you get 31 messages (mostly all the same).   I think the different messages are due to delays in the ground control system updating the satellites or the receiver not tracking particular satellites between updates.
>
> Here a couple of responses from a Thunderbolt:
>
> # GPS system message:X4W-BZXE3/HPU77G49PU1V
> # GPS system message:X4W-BZXE3/HPU77G49PU1V
> # GPS system message:X4W-BZXE3/HPU77G49PU1V
> # GPS system message:X4W-BZXE3/HPU77G49PU1V
> # GPS system message:X4W-BZXE3/HPU77G49PU1V
> # GPS system message:Z9Mx69BOC1 Lx+:LR3X2 Q
> # GPS system message:Z9Mx69BOC1 Lx+:LR3X2 Q
> # GPS system message:X4W-BZXE3/HPU77G49PU1V
> # GPS system message:X4W-BZXE3/HPU77G49PU1V
> # GPS system message:Z9Mx69BOC1 Lx+:LR3X2 Q
> # GPS system message:X4W-BZXE3/HPU77G49PU1V
> # GPS system message:X4W-BZXE3/HPU77G49PU1V
> # GPS system message:X4W-BZXE3/HPU77G49PU1V
> # GPS system message:X4W-BZXE3/HPU77G49PU1V
> # GPS system message:X4W-BZXE3/HPU77G49PU1V
> # GPS system message:X4W-BZXE3/HPU77G49PU1V
> # GPS system message:X4W-BZXE3/HPU77G49PU1V
> # GPS system message:X4W-BZXE3/HPU77G49PU1V
> # GPS system message:X4W-BZXE3/HPU77G49PU1V
> # GPS system message:X4W-BZXE3/HPU77G49PU1V
> # GPS system message:X4W-BZXE3/HPU77G49PU1V
> # GPS system message:X4W-BZXE3/HPU77G49PU1V
> # GPS system message:X4W-BZXE3/HPU77G49PU1V
> # GPS system message:X4W-BZXE3/HPU77G49PU1V
> # GPS system message:X4W-BZXE3/HPU77G49PU1V
> # GPS system message:X4W-BZXE3/HPU77G49PU1V
> # GPS system message:X4W-BZXE3/HPU77G49PU1V
> # GPS system message:X4W-BZXE3/HPU77G49PU1V
> # GPS system message:X4W-BZXE3/HPU77G49PU1V
> # GPS system message:X4W-BZXE3/HPU77G49PU1V
> # GPS system message:X4W-BZXE3/HPU77G49PU1V
>
>
> # GPS system message:E:S4.A2'3'A65/C5M8 UQO
> # GPS system message:E:S4.A2'3'A65/C5M8 UQO
> # GPS system message:E:S4.A2'3'A65/C5M8 UQO
> # GPS system message:E:S4.A2'3'A65/C5M8 UQO
> # GPS system message:E:S4.A2'3'A65/C5M8 UQO
> # GPS system message:5FT16X78CN53GVWVF1/8BW
> # GPS system message:5FT16X78CN53GVWVF1/8BW
> # GPS system message:E:S4.A2'3'A65/C5M8 UQO
> # GPS system message:E:S4.A2'3'A65/C5M8 UQO
> # GPS system message:5FT16X78CN53GVWVF1/8BW
> # GPS system message:E:S4.A2'3'A65/C5M8 UQO
> # GPS system message:E:S4.A2'3'A65/C5M8 UQO
> # GPS system message:E:S4.A2'3'A65/C5M8 UQO
> # GPS system message:E:S4.A2'3'A65/C5M8 UQO
> # GPS system message:E:S4.A2'3'A65/C5M8 UQO
> # GPS system message:E:S4.A2'3'A65/C5M8 UQO
> # GPS system message:E:S4.A2'3'A65/C5M8 UQO
> # GPS system message:E:S4.A2'3'A65/C5M8 UQO
> # GPS system message:E:S4.A2'3'A65/C5M8 UQO
> # GPS system message:E:S4.A2'3'A65/C5M8 UQO
> # GPS system message:E:S4.A2'3'A65/C5M8 UQO
> # GPS system message:E:S4.A2'3'A65/C5M8 UQO
> # GPS system message:E:S4.A2'3'A65/C5M8 UQO
> # GPS system message:E:S4.A2'3'A65/C5M8 UQO
> # GPS system message:E:S4.A2'3'A65/C5M8 UQO
> # GPS system message:E:S4.A2'3'A65/C5M8 UQO
> # GPS system message:E:S4.A2'3'A65/C5M8 UQO
> # GPS system message:E:S4.A2'3'A65/C5M8 UQO
> # GPS system message:E:S4.A2'3'A65/C5M8 UQO
> # GPS system message:E:S4.A2'3'A65/C5M8 UQO
> # GPS system message:E:S4.A2'3'A65/C5M8 UQO
>
> ----------------
>
>> I wonder how many secret services are parasites on the commercial
> TV transponders
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