[time-nuts] Best location for a GPS antenna...?

Chris Albertson albertson.chris at gmail.com
Wed Apr 11 17:17:55 UTC 2012


On Wed, Apr 11, 2012 at 7:19 AM, Bob Bownes <bownes at gmail.com> wrote:

> The issue is that this treats the t'bolt as a sacrificial item. I would
> contend that, at a cost of $80-90, you could spend far more time and effort
> trying to isolate, amplify, correct, and bias the antenna than that is
> worth. Effort and gear that would need to be replaced every time

I thought of that right after I suggested using fiber data lines.
You'd loose a few expensive t-bolts.    But I think there is a better
and cheaper way to go:   Buy a cheap Motorola Oncore receiver.   The
Oncore UT costs all of about $18 on eBay, buy four of them.    The
only signal you need to bring into the workroom from an Oncore is PPS
and that is "way easy" to do using fiber.   The other signals (rs232)
can be connected as needed and that is not often.  Then you build a
"standard" GSPDO in the workshop.    The initial cost is lower and the
engineering is simple (because only the PPS has to go over fiber)

The Oncore and GPSDO can give as good of result as the t-bolt.  It
mostly depends on how good the OCXO is, maybe even you build two
GPSDOs running off the same PPS the second one being  Rubinium based.
My $35 Rb can holdover for many weeks (at the level I need) if GPS is
down.

Then you can install the t-bolt with an antenna you can disconnect and
only use the t-bolt now and then during good wearer to double check
the GPSDO that you can leave running 24x7


Chris Albertson
Redondo Beach, California



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