[time-nuts] Thunderbolt - trouble locking with some types of antennas

[Brooke Clarke]

Hi Jerry:

The Trimble is the oldest mass produced GPS receiver I know of and because the early receivers used high gain antennas 
it seems that Trimble kept that idea for the newer designs. They like about 41 dB gain between the antenna and the input 
to the receiver.
http://www.prc68.com/I/Trimpack.shtml#Ant
Newer designs probably place that gain in the front end rather than at the antenna.  But having around 20 dB of gain at 
the antenna gretly decreases the effect of feed line loss on noise figure.

-- 
Have Fun,

Brooke Clarke
http://www.PRC68.com
http://www.end2partygovernment.com/2012Issues.html

-------- Original Message --------
> Due to access problems, I run my Thunderbolt with a Symmetricom 58532A
> antenna placed indoor near a window facing South… can’t get much worse but
> most of the time it will be locked onto 3 or 4 satellites.    I recently
> bought a www.leobodnar.com <http://www.leobodnar.com>  GPSDO for my SDR ham
> radio setup.  I was very surprised to find that this minimalist GPSDO using
> a small patch antenna with internal LNA placed near my window had satellite
> & PPL lock within a few seconds.  It requires 3-4 satellite locks for its
> PPL.  However, when I attached the patch antenna to my Thunderbolt –
> satellite signal strength were zero or minus for all satellites.  The specs
> for the patch antenna are listed below.
>
>   
>
> I would appreciate any advice understanding this behavior.
>
>   
>
> Jerry NY2KW
>
>   
>
> Center Frequency 1575.42MHz±3 MHz
>
> V.S.W.R 1.5:1
>
> Band Width ±5 MHz
>
> Impendence 50 ohm
>
> Peak Gain >3dBic Based on 7×7cm ground plane
>
> Gain Coverage >-4dBic at –90°<0<+90°(over 75% Volume)
>
> Polarization RHCP
>
> LNA/Filter
>
> LNA Gain (Without cable) 28+/-3dB
>
> Noise Figure 1.5dB Typ.
>
> Filter Out Band Attenuation (f° =1575.42MHz)
>
> 7dB Min f0+/-20MHZ
>
> 20dB Min f0+/-50MHZ
>
> 30dB Min f0+/-100MHZ
>
> V.S.W.R <2.0
>
> DC Voltage 2.7V/3.0V/3.3V/5.0V/3.0V to 5.0V/other
>
> DC Current 5mA /11mA/15mA Max
>
>   
>
>   
>
>   
>
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