[time-nuts] Outdoor GPS Antenna Selection

[Tom Miller]

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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