[time-nuts] Outdoor GPS Antenna Selection

Duane Wheaton dwheaton at cheerful.com
Sun Jan 7 22:59:50 EST 2018

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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