[time-nuts] gps timing antennas

[Rob Kimberley]

Matt,

The dome type antennae usually found in timing receivers do have a couple of
additional features over flat patch types.

1) Physical design for better performance in rain and snow (especially the
latter). 

2) Additional filtering for improved performance in high noise environments.
On this, I quote personal experience when installing a Datum product a few
years back on a TV transmitter site. The second harmonic of one of the
channel carriers was very close to the GPS L1 frequency, and the receiver
had problems tracking. We changed the antenna to a Trimble Bullet II HE (?)
which had a 3 pole filter, and problems disappeared. I'm currently using the
Vic-100 from Matsushita
http://pewa.panasonic.com/emp/products/gps_pdf/vic100_2004.pdf here in the
UK on my Odetics CommSync (antennae inside building under a concrete roof).


Rob Kimberley

-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of Matt Ettus
Sent: 13 February 2008 09:22
To: Discussion of precise time and frequency measurement
Subject: [time-nuts] gps timing antennas

Is there really anything in particular which is different about the
antenna requirements of timing receivers as compared to ordinary
high-quality receivers?  The timing antennas seem to be in pointy
radomes, so that tells me they are probably quad-helixes rather than
patch antennas.  How is that advantageous for timing in particular?

Thanks,
Matt

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