[time-nuts] Outdoor GPS Antenna Selection

[Richard Solomon]

Just being curious, I took 100' of RG-174 and connected one of those

"Hockey Puck" antennas to one of my Trimble Thunderbolts. Stuck the

antenna on a south facing window and had no trouble getting a lock.


I did not do any fine measurements, just looked at TBoltMon.


73, Dick, W1KSZ


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________________________________
From: time-nuts <time-nuts-bounces at febo.com> on behalf of Tom Miller <tmiller11147 at verizon.net>
Sent: Sunday, January 7, 2018 11:55:25 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Outdoor GPS Antenna Selection

Good quality RG6 has less loss and the mismatch is small. You see a lot of
GPS receivers and antennas with F connectors even though they generally are
50 ohms. 26 dB of gain should work fine for 20 feet of RG6. Probably also
good for good RG58.





----- Original Message -----
From: "Duane Wheaton" <dwheaton at cheerful.com>
To: <time-nuts at febo.com>
Sent: Sunday, January 07, 2018 10:59 PM
Subject: [time-nuts] Outdoor GPS Antenna Selection


I'm selecting an outdoors antenna for a Jupiter Pico T Timing GPS
(TU36-D400-020) but don't clearly understand what "dB" rating of amplified
antenna to use. From web references, it looks like the degree of
amplification required is dependent on 1.) The length of run of coax
lead-in, combined with the characteristic loss of the type of coax used 2.)
The amount of amplification needed to increase the very weak GPS signal to
the range the receiver requires it. If I'm running 20 feet of RG-58, would a
26dB antenna be sufficient?

The datasheet for the receiver family states, "1575.42 MHz at a level
between –115 dBm and –133 dBm into a 50 Ω impedance." So the receiver needs
at max a -115 dBm signal. The typical received signal power from a GPS
satellite is −127.5 dBm. So it looks like I need to amplify the RF signal
for the GPS receiver requirements + compensate for the high loss of the GHz
signal traveling through ordinary RG-58 coax. Am I on track, here?
Recommendations?

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