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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