How about a laser diode and pin photo detector? You should be able to get
nanosecond resolution with light.
----- Original Message -----
From: "Tim Shoppa" <tsho...@gmail.com>
To: "Discussion of precise time and frequency measurement"
<time-nuts@febo.com>
Sent: Thursday, May 07, 2015 2:43 PM
Subject: Re: [time-nuts] Important parameters for a GPS/GNSS antenna
Personally I would be happy with PPS time resolution at 10 nanoseconds but
others would want better than a nanosecond.
Gotcha with modulating the PPS onto a RF carrier, is that for time
resolution of 1 nanosecond, you would end up using a Gigahertz of
bandwidth.
Tim N3QE
On Thu, May 7, 2015 at 11:49 AM, John Ackermann N8UR <j...@febo.com> wrote:
Just put the GPS antenna, receiver, battery, and a low power RF
transmitter modulated by the PPS (wide bandwidth = fast edge time) on the
turntable, then use an appropriate receiver to demodulate the PPS and
feed
it to the rest of the system. Put the RX antenna directly above (or
below)
the turntable so the path length remains close to constant. Using FM
might
also remove Doppler effects from the received pulse.
On 5/7/2015 11:18 AM, Tom Van Baak wrote:
I wonder if anybody ever made a rotating GPS antenna to average out the
X-Y phase-center offset ?
Of course, this does not really work with a gps antenna, unless you
put the whole receiver onto the rotary table. But then you shift
the problem onto the PPS output (note: amplitude noise translates
into phase noise).
Attila,
My thought was to put PHK's proposed experiment entirely on the rotating
table: antenna, receiver, local Cs standard, laptop, and battery. You
could
also get interesting data if you slightly offset the antenna from the
center. It would make the ultimate GPS Spirograph. (for those of you
under
40, http://en.wikipedia.org/wiki/Spirograph will explain)
/tvb
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