GPS Antenna


I am trying to hook up a GPS Patch antenna with LNA up to a GPS module without a lot of luck. Its actually rather strange, If I hook the patch up with a 5m long cable that it came with ( I pulled apart a normal GPS antenna) it works fine but when I detach the cable and use a shorter one (5-10cm) it won't work.

Does anyone have any suggestions



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reduce the voltage to the lna? add a small risistor in series with the coax? maybe the lna is unstable?

Reply to
Ed /:-}


Does it work with a 5m lead made of your cable? Otherwise is the group delay change affecting the module operation?

Alternatively, is your short cable just plain faulty?



Reply to
Ken Taylor

Thanks for suggestions guys,

I have tried a 1R resistor in series with the signal wire, do you think it would be a good idea to add one to the GND rail as well to isolate it a bit? I have tried a few different cables and im sure I don't have a faulty one.. I have even tried cutting a piece of the original cable to try but no go. I am working on 2 of the same units, I managed to get one to work with a 1R resistor in series but its operation is not as good as norml... I have put it to rest for today, a fresh start tomorrow.



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If it is very close (< a metre??) , the module could be re-radiating the signal and it is being picked up by the patch antenna, causing overload and signal distortion. You may be able to confirm this by experiment. eg. shielding the module, moving the antenna around.

A normal one ohm resistor could have enough inductance (a few nano Henries) to significantly attenuate the 1.5GHz signal.

HTH, Glenn.

AJ wrote:

Reply to
Glenn Baddeley

Hi Glenn

Actually it is very close, about 3 cm. I have been testing with re-radiating antenna and moving it away a bit form the antenna doesn't seem to make a lot of difference. I will try some shielding today to see if that makes any difference. I have also ordered a few inductors to see if that will help at all!

Thanks for your suggestion



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