[time-nuts] More Z3801/Tbolt comparisons

Roy Phillips phill.r1 at btinternet.com
Fri Sep 4 10:17:31 UTC 2009

Interesting stuff - -
I'm not anti Racal, in fact I have a Racal T & F Mainframe, fed by a Trimble 
NTX, and the T&F Mainframe is very well made and performs in an excellent 
manner. But,  - -  - Racal 19## Counters are something else - - I got rid of 
mine some years back, not only the ongoing problems with the key-pad, but I 
don't think they put much cost into the oven osc. Perhaps you should 
consider moving on to an HP or other quality counter, "you deserve it"

----- Original Message ----- 
From: "John Green" <wpxs472 at gmail.com>
To: <time-nuts at febo.com>
Sent: Thursday, September 03, 2009 8:05 PM
Subject: [time-nuts] More Z3801/Tbolt comparisons

> Yesterday, I thought the Tbolt was wandering around too much. So, I did a
> factory reset and started a new 5K
> fix self survey. At about the same time, I started a new self survey on 
> the
> Z3801 thinking that if they were
> both looking at the same satellites with the same antenna at the same 
> time,
> they might be closer together.
> When I arrived back at work this morning, I looked at the final positions
> they had arrived at. The latitude
> difference was .000017 deg. and Longitude was .000026 deg. Great. This is
> probably within the margin of error
> of how they report. But, the altitude was 36.05 meters different. That, I
> can't explain. I have been looking
> at the time difference all morning and it seems to cycle +/- 6 ns every
> couple of minutes. It also seems to move
> maybe 30 nsec every hour or so.This also seems to be cyclic. I also see
> sudden jumps of around 4 to 5 nsec. I
> assume this is due to DAC voltage corrections. I thought some of this 
> might
> be due to the Z3801 since I was using
> it as the reference to the 1992. I switched back to the internal reference
> and couldn't tell any difference.
> Could some of this still be the 1992? I noticed the Tbolt was set to not
> look at any satellites below 10 deg.
> I changed that to 0 deg. like the Z3801 and it didn't seem to make a
> difference. I am going to let a Rb start
> warming up and use it as a reference later to see if some of what I am
> seeing is the Z3801. Anyone have any ideas
> why the altitude is so much different? I am going to look at a topo map to
> see what it says. I might also change
> the disciplining constants of the Tbolt to see if it makes a difference. I
> can always do a factory reset later.  None of this is
> meant to say that the Tbolt isn't as good as the Z3801. I just wanted to 
> see
> what they looked like compared to each other.
> To folks used to seeing charts and exact numbers these casual observations
> may be a bit annoying. I haven't
> yet been able to use the GPIB facilities of my 1992. Hope to later. These
> are only meant to be casual
> observations. Though I trust what I see and read from my instruments, 
> these
> aren't meant to be written in stone or quoted
> as specifications. Just some things to think about.
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