[time-nuts] Source for Trimble Bullet GPS antennas?

[ewkehren at aol.com]

I agree it is the antenna. I have a Volute left over from a boat GPS and it 
 is serving me well. I have no idea how well it prevents multi path,  but I 
get a strong signal. A little trivia, the first GPS receiver used a  Volute
Bert Kehren Miami
 
 
In a message dated 12/16/2009 9:29:03 P.M. Eastern Standard Time,  
charles_steinmetz at lavabit.com writes:

Bob  wrote:

>The Lucent Bullet is rated as a 26 +/-3 db LNA  device.
>The Trimble Bullet is rated as 30 +/-3 db at 3.3 volts ( for  the III 
model)
>The Trimble Bullet II is rated as 35 db at 5  volts
>A lot of the simple antennas are up around 45 db at 3.3  volts.
>The less specified parameter is noise figure. The Bullet II has  a 
>2.75 db nf, the III at 3.3 db. I haven't seen a number on the Lucent  part.
>These days a 1.5 db noise figure is not all that expensive at GPS  
>frequencies.
>I suspect that none of that really helps  straighten out any of this ....

As another Time Nut pointed out in an  offlist e-mail, like any other 
radio system, it's not the LNA that does  the serious work, but rather 
the physical antenna.  In the case of  GPS antennas, the LNA primarily 
compensates for losses in the feed  coax.  Higher gain can lead to 
overload of the LNA, so it's not  necessarily a panacea -- 
particularly in high-density VHF/UHF  environments.  Reportedly, much 
better performance can be had from  larger and more sophisticated 
antenna structures.

I have RF design  experience, based on which I wouldn't put any faith 
in noise figure specs  from any but the most reputable suppliers.  I 
assume Trimble is one  such, and I know that Andrew (the apparent OEM 
supplier to Lucent)  is.  But most others should probably be taken 
with a large rocks of  salt.

Best  regards,

Charles





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