Rafael, can you post a picture of your setup, like one where its
working, and another where it's not working.  Sometimes position of
components can a the major issue as Richard said.


Shawn Wilton
Junior in CpE
MicroBiologist

Phone: (503) 881-2707
Email: shawn@black9.net

http://black9.net

Richard.Prosser@POWERWARE.COM wrote:
> Definitely sounds like the RF is getting into the GPS input stage &
> blocking its signal.
> What sort of access do you have to the GPS antennae connection. Can you add
> a trap such as a 1/4 wave ( at ~145MHz) length of short circuited coax. -
> Or even a simple hairpin coil across the input terminals may have enough
> inductance to be insignificant at the GPS frequency. e.g - 20mm wire ~20nH
> ? = 188 ohms (~1dB)at 1.5GHz, v/s 18.2 ohms (~7.7dB) at 145MHz. - Maybe not
> enough - a 1/4 wave trap would be much better..
>
> Otherwise - maybe you could mount the GPS antennae directly below the 2m
> one so the VHF signal pickup is minimal.
> Or is there a waveguide type filter you could place over the GPS antennae
> to attenuate low frequency pickup.?
>
> Richard P
>
>
>
>     This is an interesting issue. I made several tests yesterday, and
> when the GPS is in the floor of the garage, the system works! As i put
> it in higher places the interference goes getting higher until the same
> high of the radio's antenna, when the transmitted signal gets muted!
>
>
>     I think it's a mag antenna. It's mounted in the top of the car roof.
>
> Rafael.
>
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