Decoding local-GPS like MDC

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RedPenguin

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Probably everyone knows about WinMDCD, which works extremely well in my area.

Though, my question is, is there a similar method to decode GPS?

In my area there is a GPS system which uses a UHF-radio frequency, besides just GPS.

It kinda sounds like a digital control channel, I think it's mainly used to send back GPS info to a computer system and to receive messages from said computer system.

So I guess, the process wouldn't really be decoding GPS, but the communication between unit and computer.
 

Squad10

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Is there a chance you ran across a DGPS frequency..

DGPS on Garmin Receivers

Most likely it is a Trimble Navigation radio modem transmitting RTK data from their CORS station to field survey receivers. Using RTK data, a field receiver will achieve real-time sub-centimeter position accuracy.

The Trimble radio modem uses GMSK modulation at 9.6kbs.
 

RedPenguin

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Well.....

Well, here is what I know about the system:

It uses a normal 453.xxx frequency for communication.

The dispatcher can send messages to the "Vector" and request a "receipt".

So I was curious, if you can decode MDC, can you actually read these messages being sent, if you wanted?

I know Avail Technologies is behind the entire system.
 

Squad10

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It appears that Avail Technologies use Mentor Engineering and CalAmp/DataRadio for the moile data equipment. You would need to use the same modem technology in attempt to demodulate the data. Even if you were able to demodulate the data message it may or may not be in a readable format.
 

RedPenguin

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Yea....

It appears that Avail Technologies use Mentor Engineering and CalAmp/DataRadio for the moile data equipment. You would need to use the same modem technology in attempt to demodulate the data. Even if you were able to demodulate the data message it may or may not be in a readable format.
Figures......

I tried looking at their site to find the company name/models but I only have about a minute or so, then had college class.
 

Squad10

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The Mentor Engineering MDC device spec. says the internal radio modem operates at 4800 - 9600 bps. They probably use GMSK or 4-level FSK for modulation.
 

RedPenguin

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Well.....

.................
I see what you mean, but their site, isn't one of the friendliest I have ever seen.

I mean they didn't just put a link up that said, "Equipment We Use!" obviously.
 
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