[time-nuts] Trimble Thunderbolt - Receive Sensistivity

J. L. Trantham jltran at worldnet.att.net
Thu Aug 28 22:39:09 EDT 2008


When I compared the function of the Thunderbolt to my Z3816A, the number of
tracked satellites was smaller on the Thunderbolt.  However, the Signal
Level Mask is set to 4.0 on the Thunderbolt.  After I reset it to 1.0, they
tracked the same (and number of) satellites.

This I did with TBoltMon under 'Setup', 'GPS Receiver' which takes you to
'Receiver Configuration'.  Change the Signal Level Mask (AMU) to the desired
number then 'Set Receiver'.  I also hit 'Save Segment' though I do not know
if this is a required step.

Joe

-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of Predrag Dukic
Sent: Thursday, August 28, 2008 6:05 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Trimble Thunderbolt - Receive Sensistivity



I also had the same feeling until I changed the position of the 
antenna from eastern side of the building to the southern.

At least two usable svs more on the average...

P. Dukic




At 19:05 28.8.2008, you 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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