[time-nuts] GPS antenna gain

Reid, John H John.Reid at team.telstra.com
Wed Jan 14 18:20:57 EST 2009



Message: 3
Date: Wed, 14 Jan 2009 14:52:32 -0500

Hello Gents (and Ladies),

I am in a bit of a quandary.  I have been using a Synergy Timing 3000
GPS antenna in a test set-up for some time and recently got a VIC-100
antenna, thinking that its greater spec-sheet gain (38dBi vs 25dB(i?)
typical) would allow for a longer down-lead in the field if
needed.  Upon testing, the VIC-100 appears to have around 10dB LESS
gain than the Timing 3000 and I would say is barely adequate on 25 ft
of LMR-195!  I used a switched attenuator pad with 2 DC blocks for
the test and set each antenna to comparable SNR levels as indicated
using TAC32 with an M12M-T.  I have tried a second VIC-100 with the
same results.  Would anyone have an explanation for this?

David,

the VIC-100 is an amplified antenna, and needs DC continuity on the antenna cable.
The Navtech description is "VIC-100 Active Antenna", 'active' in this case being the giveaway.

Regards,
John.





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