PSN-L Email List Message

Subject: Re: trouble shooting GPS antenna
From: Hammonds hammond@...........
Date: Thu, 10 Jan 2002 06:59:54 -0900

Angel, I remember something about not exceeding a certain cable length 
between the
receiver and the antenna.  Had to do with overall impedance, loss, and 
loading.  What I did
is keep the antenna cable length as it came from Synergy and move the 
receiver then wire in whatever
length of RS-232 cable I needed to get to the PC.


Bob Hammond
Alaska PSN

At 06:50 AM 1/10/02, you wrote:
>   I can't seem to find my coax loss table at the moment, but I suspect 
> your problem lies
>with the RG174.  You're probably loosing 5db of signal in the cable 
>alone.  RG174 has
>very poor characteristics even in the low VHF bands.  GPS is high 
>UHF.  Add to this the
>inevitable losses from the splices and various junctions between the 
>antenna and the
>first amplifier/mixer, and you end up with a receiver that can only hear 
>satellites that
>are directly overhead, where the signal is the strongest, or none at 
>all.  UHF/Microwave
>coax is hard to find, and expensive, but worth it.
>Good Luck,
>"angel@chiriqui" wrote:
> > Hello,
> >
> > Yesterday I got and SDR system up with one of the GPS systems we
> > bought as a group.  To lengthen the antenna I spliced in about 20 ft of 
> RG174 into the
> > little 5 foot cable of the antenna that came with the units.  Hooked
> > it all up and It worked well.
> >
> > Last night and today all got was and SDR error message stating "not
> > enough GPS stat's being tracked".
> >
> > I replaced the antenna with one that I got from Synergy and had
> > reserved for another installation and the problem disappeared.
> >
> > Any idea on how to test or trouble shoot this antenna???
> >
> > Best regards,
> > angel                          mailto:angel@............
> >
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