[Elecraft] WTB Trimble ThunderBolt for K3EXREF / QS1R

[Fred Townsend]

I think these posts contain much wisdom. I'd like to add a little to what
Dave has said.

>Remember too, that the GPS antenna will need 
>a clear view of the sky for the TB to function correctly.

Many GPS antennas are sold with a pre-attached coax. Most antennas contain a
preamp as well. Ever wonder why?

The coax supplied by many is very small allowing it to be easily concealed
in a car's headliner. In an apartment or basement shack the distance to
clear view may beyond the pre-supplied coax. Before you extend that coax
take a look at the total attenuation.

The GPS frequencies are approximately 1.6 GHz.  At 1.6 GHz the attenuation
of the OEM coax used by many runs about 1 db per foot. RG174 is 0.35 and
RG58 0.2 db per foot. You can also figure about a db per connector. With
this kind of attenuation a preamp is essential. Even with a preamp a long
run of coax is deadly to GPS.  Caveat Emptor.

73,
Fred, AE6QL



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