[time-nuts] GPS antenna gain

[David McGaw]

OK, lesson learned: check all conditions.  The test system was 
feeding 3V rather than 5V to the antenna.  Once the correct voltage 
is used, the characteristics make more sense.  In fact, with a 25 ft. 
LMR-195 lead-in the VIC-100 gives almost unchanged SNR with 25dB 
attenuation added, -3dB with 30dB attenuation.  The Timing 3000 shows 
-3dB change in SNR with 10 dB attenuation - quite a difference.

David

At 10:23 PM 1/14/2009, you wrote:
>Yes, more correctly I used 2 power inserters, one each way, to shunt
>the antenna power around the attenuator so that the antenna is
>powered and the GPS receiver sees the antenna as connected.
>
>David
>
>At 08:50 PM 1/14/2009, you wrote:
> >And I did not make myself clear.
> >
> >If you were using power inserters, I expect one was used coming from
> >your GPS receiver and you shunted the DC voltage around the attenuator
> >and re-inserted DC voltage back to the antenna.
> >
> >
> >
> >Brian Kirby wrote:
> > > Can we clarify, you were using the DC blocks or were they power 
> inserters ?
> > >
> > > Brian
> > >
> > > David McGaw wrote:
> > >> 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?
> > >>
> > >> Thanks,
> > >>
> > >> David McGaw N1HAC
> > >>
> > >>
> > >>
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