[time-nuts] Newby with questions

[Bob Camp]

Hi

The TBolt will not shut off it's output when it goes into holdover. It will
stay within 0.1 ppm for a few years in holdover mode, so it may not actually
be an issue. 

Standard distribution is not an easy task. You don't want to trade one bad
piece of string for another. There are two basic approaches:

1) Use something like the Spectacom tap system where you have a few trunk
lines and drops at each stack of gear. Ideally you would have a drop per
device.

2) Use properly designed distribution amplifiers. There are a lot of people
who make them. Generally you wind up with one "master" driving a set of
"children" out on the floor. A port per device is ideal. You often see
setups that are less than ideal. 

In both cases you are trying to get a quiet signal to each device. That
involves isolation, low noise amplification, and proper levels. It's amazing
just how hard that all is to do if you have 100,000 square feet of floor to
cover. 

All this stuff can be bought new for a lot of money (with nice things like
warranties). It can also be found on the auction sites in pretty good shape
for a whole lot less. Even used gear that's designed for the purpose will do
a better job than something you lash up.

Bob

-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of David VanHorn
Sent: Monday, February 28, 2011 12:45 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Newby with questions


The 24 GPS satellites are in orbits that never pass over the  poles.
I think they are about 60 degree inclinations.   By your description
you must be in the northern hemisphere.  If you can,  set up your
antenna so it can see to the south and don't worry if the view of the
north is blocked because as you found there is nothing to see there.


I see!  So I could move the antennas closer to the north side of the
skylight, letting the skylight wall on the north side get up around 60
degrees, so that my view to the south is more optimized. 

I also see the notes on the temp sensor, just ordered some rev C parts that
I can change out here as needed.


I'm going up on the forklift today to connect the second feed (didn't have
enough adaptors Friday for N-F) and I'll nudge the positioning a bit, then I
can do the survey on the other antenna.


I understand that the Tbolt should be giving me WAY better than 1PPM, but
that's exactly what I wanted.  Until I started pushing this issue, we didn't
calibrate anything, and our test gear was in constant disagreement.  If you
can't measure it, you can't improve it, and I'm tired of measuring with
unmarked string.. <VBG>

My next problem to solve, is distributing the signal through the production
floor. I won't need phase accuracy between the drops, but I don't want to
induce any significant error.  My initial thought was simply to amplify and
split like CATV drops, but I'm seeing that this may not be the best
approach.  I have a 75 ohm video distribution amp on order that will serve
my immediate needs, maybe something better later on.

Question:  Is there a way to have the Tbolt shut off the 10 MHz output if it
is not reliable? I'd rather have no signal than an unreliable signal.



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