# GPS antenna conversion



## AKA Arizona (Jul 22, 2003)

I am not sure where to start looking so I started here. I have a 2003 Yukon XL it has an XM satellite built into the radio with the antenna factory mounted on the roof opposite the onstar antenna. I will never use the XM besides my mp3 player and 6 disk changer I have no need to pay to listen to the radio. I do however, have a need for an external GPS antenna, does anybody know or can anybody direct me to a site that might explane how I can convert my XM antenna for use as an external GPS antenna.


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## kiwiguy (Aug 17, 2003)

GPS uses frequencies in the 1200-1500 MHz region, XM satellites are around twice that frequency according to my research.

So the XP antenna is likely not well suited to GPS as I see it, it may never have been designed for such a wide frequency range in all probability.


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## AKA Arizona (Jul 22, 2003)

Something I never considered, I figured GPS and satellite radios would run in the same ranges.


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## AKA Arizona (Jul 22, 2003)

**Bump**


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## AKA Arizona (Jul 22, 2003)

**Bump**


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## JohnWill (Oct 19, 2002)

I think the question was answered! If the frequencies are that far apart, the antenna is poorly suited for the task. What more are you looking for?


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## kiwiguy (Aug 17, 2003)

Agreed, I too thought I had answered it. But just in case, the exact figures are:

GPS:
"All three signals, NM, C/A and P(Y), are mixed together and sent on the primary radio channel, L1, at *1575.42 MHz*. The P(Y) signal is also broadcast alone on the L2 channel, *1227.60 MHz*. Several additional frequencies are used for unrelated purposes."

XM:
"The XM signal uses 12.5 MHz of the S band:* 2332.5 to 2345.0 MHz*"

So I can only repeat, using the XM antenna should be incredibly poor in performance for GPS purposes. Any conversion cable or adapter cost would be better put towards the correct GPS antenna for your model of GPS.

We have no idea what GPS you have as to what antenna is needed or available for it.


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## AKA Arizona (Jul 22, 2003)

Its not that I don't believe you, Just looking for that little extra. I did find some info about hacking the GPS in my onstar and that might give me the same end results. 

Now if I could just figure out how to hack the cell phone, not to steal service mind you but to use my it with my current Cingular account without all the extra BS, I see I can use a verizon account but me do not have verizion in our area. Or at least use the hands free features with my phone, some kind of bluetooth connection.


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## O111111O (Aug 27, 2005)

XM uses low noise block waveguides and locally oscillated signal to downconvert SAT to IF freq.

GPS is similar. Issue is the SWR it going to be piss poor for a different band.


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## AKA Arizona (Jul 22, 2003)

Yes I have discovered that, I am going to purse the onstar gps tap, I found a car mount that will allow a wired gps to connect to my pda via an rj11. That was biggest issue I had no way of connecting a gps except via bluetooth, I wanted to add the external antenna to the bluetooth but that is no longer the issue.

Now if I could just tap that cell phone.


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