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[time-freq] Efratom GPS Antenna

Eric Lemmon wb6fly at verizon.net
Mon Jul 5 15:45:03 UTC 2010


Bobby,

Thanks for the suggestions.  It definitely is an active antenna, but its
operating voltage is the unknown.  I have no tech data on it, and I am
reluctant to "play" with it until I know more about it.  I have a commercial
GPS-disciplined frequency standard (possibly made by Symmetricom) that can
be adjusted for 3, 5.5, 9, or 12 VDC to feed the remote antenna over the
cable.  Whether my Efratom antenna was made for this device or not is
unknown.  The mounting hardware that was packaged with the antenna is
typical of that used for GPS timing systems at cellular and LMR simulcast
sites.

I do know that Efratom has passed through several owners, including Ball
Aerospace, Datum Irvine, and Symmetricom.  I have written to Symmetricom in
hopes that they can provide some tech data.

73, Eric Lemmon WB6FLY
 

-----Original Message-----
From: time-freq-bounces at tapr.org [mailto:time-freq-bounces at tapr.org] On
Behalf Of 2005 at bobby.net
Sent: Monday, July 05, 2010 7:59 AM
To: time-freq at tapr.org
Subject: Re: [time-freq] Efratom GPS Antenna


First, I don't know anything about this antenna. 

If you can't find docs or data anywhere...
Assuming (which might be a mistake) it is an active antenna, and that DC is
fed up the coax, here are some ideas you can try. 

First using a multimeter check for an open, diode junction, or perhaps a DC
short on the coax.

If it looks like an active antenna, try applying 3V to it via your receiver.
Look at the signal quality indicators, you might only have signal strength
for the individual SVs being tracked, or worse only the number of SVs being
tracked. You can (and probably should) also monitor the antenna current
supply for rapid ramping.

Slowly increase the voltage to 3.3v and see if the numbers get better or
worse. 
It is unlikely this antenna requires any more than 5V, so I would not go
higher than without some other information indicating a higher voltage was
used.

Good luck.

73, Bobby k4bga

<snip>




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