[time-nuts] Trimble Thunderbolt - Receive Sensistivity

[Scott Mace]

Both of the thunderbolts I have usually see 7-8 satellites, SNRs from 35-50,
antenna is on the roof with about 150ft of LMR-400 and going through 2 4-port
distribution splitter/amps.  I use the belden equiv of LMR-195 for all
connections between the receivers and the amps.  Both thunderbolts seem to
compare well to the M12+ based Fury, and do usually better than the 6-channel VP z3801a.

	Scott

Mark Sims wrote:
> The Thunderbolt does not seem to be the most sensitive receiver around,  but it does not seem particularly bad.  Sensitivity in a time receiver can be a bad thing...  more sensitivity tends to make it more susceptible to multipath, etc.  These things were meant to be mounted on cell towers, etc where they have a pretty clear view of the sky.  Once you have that,  you don't need high sensitivity.  Also their proximity to high power RF transmitters makes overly sensitive front ends a problem.
> 
> On the subject of GPS amplifiers...  adding external amplification to a GPS may not improve its performance and can actually degrade it.  All amplifiers amplify signal and noise,  plus distort everything in the process. (fundamental laws of the universe: 1) You can't get something for nothing,  2) You can't break even,  3) You'll die trying)   Ideally,  you want the amplifier at  the antenna and you want the amplification to match the cable loss and no more.  Generally GPS receivers with poor sensitivity have poorly designed front ends or signal processing.  Yelling in their ears won't make them work any better.
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