[time-nuts] Z3801A & ThunderBolt USING SAME ANTENNA?

Didier Juges didier at cox.net
Tue Jul 8 21:59:44 EDT 2008

If the cable is long enough, the discontinuities brought by using a BNC
connector should not be too much of a problem, unless you are trying to
extract the very last ounce of performance from the Thunderbolt.
A long cable will have significant attenuation, and that will absorb most of
the reflections caused by the impedance mismatch and bring them down to the
noise level.

This subject has been covered at length not very long ago (a few months?),
so a look through the archives might bring back the thread.

You might want to read the Thunderbolt manual to get Trimble's official
position on the subject.

Trimble has done a good job of confusing people by specifying their
equipment for 50 ohm operation but recommending 75 ohm cable and using F
connectors on the Thunderbolt and the Bullet antenna.

I surmise that for the Thunderbolt's intended application (cell site
synchronization), the difference was not worth worrying about. For the true
Time-Nuts, that may not be good enough.

Didier KO4BB

> -----Original Message-----
> From: time-nuts-bounces at febo.com 
> [mailto:time-nuts-bounces at febo.com] On Behalf Of jshank
> Sent: Tuesday, July 08, 2008 8:45 PM
> To: Discussion of precise time and frequency measurement
> Subject: [time-nuts] Z3801A & ThunderBolt USING SAME ANTENNA?
> Hi,
> I am trying to set up a Z3801A and a ThunderBolt to operate 
> off of one symmetricom 58532A antenna using a symmetricom 
> 4-port smartsplitter.  The Z3801A manual suggest using LMR 
> 400 cable which is a 50 ohm cable which is compatible with 
> the antenna.  The thunderbolt which I receive has a type F 
> connector and the thunderbolt manual suggest using 75 ohm 
> rg59 cable. Will I have a problem connecting the thunderbolt 
> to the smartsplitter using LRM400 50 ohm cable?  The 
> thunderbolt which I received came with a type f to bnc 
> connector, but isn't a bnc connector underrated to handle the 
> 1.5 GHz signal?
> Thanks,
> Jeff
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