PSN-L Email List Message
Subject: Re: trouble shooting GPS antenna
From: R&L_Thompson rlthompson@.................
Date: Thu, 10 Jan 2002 16:42:45 -0330
RG58C coax cable has a loss of 66 db per 100 metres at 1GHz*, the GPS
coarse acquisition signal
is on roughly 1.3 GHz, so the losses are higher than that. You've added about
13 metres of cable, so
you've added at least 9 db of loss in the cable alone. A good quality crimp
connector will add additional
losses, and to splice in the middle of the cable means you've added 4
connectors. I wouldn't venture
to guess what the losses are with the connectors done the way you've
described them. The cable
extension used good quality materials and practices has added not less than 10
db of loss. Using the
method you've described here, I wouldn't venture a guess at the losses, but
undoubtedly they are
much higher than 10 db.
Ron Thompson ( I teach avionics )
* Reference: - This figure comes from my copy of the ARRL UHF/Microwave
Chapter 5-16, Table 2. An alternative cable, although much larger in
diameter, would be Belden 9913
with a loss of only 15 db per 100 metres, and it should be used with good
quality adapters / connectors.
Karl Cunningham wrote:
> Hi Angel --
> I extended my GPS antenna using RG-58 coax, splicing a piece of RG-58 in
> the middle of the RG-174. I used crimp-style BNC connectors on each end of
> the RG-58 (one male, one female). I used the same type of crimp connectors
> on the RG-174, soldering the center pin and building up the jacket on the
> RG-174 with shrink tubing so the crimp BNC would have something to grab on
> Right now there is about 40' of RG-58 and it seems to work just fine.
> --On Thursday, January 10, 2002 8:26 AM -0500 "angel@chiriqui"
> > 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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