[time-nuts] GPS Timing receivers

Tom Van Baak tvb at leapsecond.com
Thu Oct 6 21:34:35 EDT 2005


> Tom,
>
> John A and I had a short antenna email earlier today, mostly about the
fact
> that both of the GPS antennas we were using died.
>
> I asked a question about certain "commercial" antennas which included the
> Timing 2000, HP 58532A and the Datum 2640NW/DE, as to wether there were
any
> opinions as to which is the better timing antenna. Neither of us has much
> of an idea, do you have any thoughts?
>
> Had

I've heard that many modern telecom GPS timing
antennas are heavily filtered since they are usually
placed in high RFI locations. This may be good for
them but I think it has negative side effects for the
kind of precise timing we do, so I'm told.

I'm going to ask Dr Clark to handle this one as he
understands GPS antennas very well. TAC -- what
I'd like to know is if patch is better than helix, if filtered
is better than unfiltered, how much amplification is
too much, vintage 1990's era antennas vs. 2005
antennas, real splitters vs. Radio Shack splitters,
antenna or preamp tempco issues, cable loss and
impedance issues, etc. At what ns level does a
groundplane start to matter. I guess what we need
is some kind of Time Nuts guide to surplus GPS
antennas.

If it's not possible to give a black and white answer
to what kind of antenna is best for a Z3801A-style
GPSDO, then at least, what are the factors that
make one better than another. And is any of this
simple to determine with experimentation? Maybe
we can all chip in and test a dozen antenna types
to find the answer or to confirm a prediction.

/tvb






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