[time-nuts] Up And Running

Fri Sep 28 15:30:51 UTC 2012

Looks good, but I would have gone for a different GPS antenna. The timing antennas are weather proof. I have a Marine grade GPS antenna, also weather proof, but the timing antennas are probably a little better since they have less response to GPS birds on the horizon. 

-----Original Message-----
From: "George Race" <george at mrrace.com>
Sender: time-nuts-bounces at febo.com
Date: Fri, 28 Sep 2012 10:53:25 
To: <time-nuts at febo.com>
Reply-To: george at mrrace.com,
	Discussion of precise time and frequency measurement
	<time-nuts at febo.com>
Subject: [time-nuts] Up And Running

Hello to all the Time-Nuts: 

 I Have been acquiring parts for a few weeks and finally have a
Thunderbolt-Trimble system up and running.

Though I would share a few pictures of what I did and how it looks now that
it is all together and working.

First, here is an overall look at what I have put together.

http://www.mrrace.com/TrimbleGPS/TrimbleParts.jpg

I had to use the attenuator to reduce the amplitude of the 10MHz signal from
the Trimble.  It was overdriving the Extron causing distortion in the output
waveform.  The 6db attenuator is just what was needed.

I was running on a temporary old GPS antenna mounted on the edge of my
garage roof for a while.  I ordered a Trimble antenna from China, took about
10 days to get here.  What a difference that made in the overall signal
strength and stability of the unit.

Here is a Lady Heather shot after running on the antenna over night.

http://www.mrrace.com/TrimbleGPS/MyLadyH.jpg

I am still having trouble knowing what all the indicators on the screen
mean, but it appears that everything is working.

Sure wish there was an index somewhere that told what each and every thing
on that screen means!

As I mentioned, the antenna arrived yesterday and I built a mount and
installed it yesterday afternoon.

Though you might like to see what I ended up doing.  We have a lot of rain,
snow, and ice here in Michigan, so I wanted to do something to protect the
antenna and connectors the best that I could from the elements.  First, here
is a picture of the antenna from China, along with the adaptor cable to get
it to an “F” connector to hook to my 50 foot RG6U cable with “F” connectors
on each end.

http://www.mrrace.com/TrimbleGPS/TrimbleAnt.jpg

Here is the mount that I built.  I am going to put it on my TV antenna mast
that is mounted on the house.  The 10 degree elevation pattern should see
open sky in all directions.

The mount is a piece of aluminum angle with a mast clamp on one end, the a
sealable tea container on the other.  The container is one of those push
button kitchen containers that has a very tight air seal when the button on
the lid is pressed in.  It really holds well, and you cannot remove the lid
when it is locked into place.  Also this configuration makes it really easy
to get to the antenna and connectors if necessary.  Just release the button
on the bottom and lift off the unit.  The “F” barrel connector through the
side of the container makes it easy to just unscrew the cable if necessary.
The seal on the container is about ¾ of an inch wide, and really holds on to
the inside of the container.

http://www.mrrace.com/TrimbleGPS/BuildingTheMount.jpg

To hold the GPS antenna in place at the top of the container, I cut a small
aluminum plate, carefully drilled 3 holes for 2-56 hardware through the top
of the container, using the aluminum plate as a template.  The antenna is
“clamped” into place by bolting the plate up against the bottom of the
antenna, inside of the container.  You can see from the next picture how the
cable connectors and antenna wire is coiled up in the bottom of the
container, and terminates on the “F” barrel connector inside.  Looks like it
is all ready to put up on the roof and connect to the cable.

http://www.mrrace.com/TrimbleGPS/ReadyToPutUp.jpg

Here it is, mounted about 25 feet above the ground, below the TV antenna.

http://www.mrrace.com/TrimbleGPS/MountedHigh.jpg

And here is a close up of the finished installation.

http://www.mrrace.com/TrimbleGPS/UpAndWorking.jpg

A lesson to be learned, about “F” connector barrels!

When I hooked up the basement end of the cable, total disappointment!  On
the screen it said in yellow letters, “Antenna Open.”

As I had tested the system end to end, BEFORE I put it all in the container,
the only place that could be a problem was that “F” connector barrel.

I brought the container back down to the bench and carefully looked at the
connections.  It was so simple, and I had caused the problem during early
bench testing of the cables.  The jumper cable from the antenna to the inner
part of the “F” connector has a extremely small diameter center conductor.
On the other hand, the RG6U cable has a greatly oversize, compared to RG59U
cable, center conductor.  In testing I had pushed the RG6U center conductor
into both ends of the “F” barrel.  This pushed the center part of the
connector to its limits, and it did not close back down when the cable was
removed.   I installed a nice brand new “F” barrel into the side of the
container.   Starting the “F” connector on the inside barrel connection, I
could feel the center conductor pushing into the connector.  Taking it all
back to the roof, tightening the “F” connectors in place, solved the
problem!

Somebody is probably going to ask, what I am using this system for?  I have
an HP synthesized signal generator and a Racal-Dana digital frequency
counter that both have provisions for a 10MHz external standard input
signal.  I wanted to have them driven by the GPS system to give me the best
possible accuracy I could get on both instruments.  

Picture of the messy work bench below!

http://www.mrrace.com/TrimbleGPS/TestEquipment.jpg

Comments and suggestion are always welcomed,

George

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