[time-nuts] GPS antenna gain

[Bruce Griffiths]

Reid, John H wrote:
> 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.
>
>
>   
John

They are both (VIC100 (20mA typical) and Synergy timing 3000 (26mA
typical)) active antennas requiring a +5V dc supply on the inner coax
conductor.

Bruce