[time-nuts] Re: HP Z3801A project update

[ed breya]

I've been wrapping up the last major sheet metal parts, and found I had 
no ground tie in for the box that holds the Z3801A's power supply. This 
is the part that holds the PS board cantilevered up over the main board, 
in its proper position that's necessarily different from original. The 
whole thing mounts on the original PS board posts on the main board. I 
found that none of these posts are tied to the main ground plane, 
contrary to what I had thought. The box is a major structure, serving as 
a plenum to control air circulation, an EMC shield, and a mounting deck 
for experimental circuits (for later on). Not good to be groundless.

I had to add some heavy grounding posts for it into the main board 
mounting scheme. It worked out well, but set me back a bit.

Before moving on to the internal battery system wrap up, since the guts 
are all in place again for a while, I decided to try talking to it with 
the old SatStat program. It took a while to find it, and I had to fix 
the COM ports board on my main computer (long story). After some grief, 
I finally got everything hooked up and running. Happily, it still works 
after all these years. This is the first time I've talked to it in over 
ten years.

It seems to all be working OK, except the reported date is slightly off 
- by about twenty years. It says it's 20 Jun 2002. The setup isn't 
optimal - it's just a little GPS antenna propped up against the office 
door glass. It only sees about three satellites, but enough to lock and 
report mostly right. I assume the date thing will either fix itself 
after some time, or maybe it's due to a bug. I've heard of various 
rollover issues and such over the years, but don't recall any details - 
since my stuff wasn't working anyway, I didn't pay much attention.

If anyone happens to know offhand, what the date issues are and any 
hopefully easy fix, I'd appreciate hearing about it.

The 1PPS TI reports typically +/- a few to 10 nSec bouncing around - I 
haven't seen it go beyond 20 so far.

The location seems right on. I found some of my notes from way back, 
when I had it hooked to a decent outdoor antenna - the coordinates are 
exactly the same. This setup is about 5-10 m away from the original 
location.

The EFC initially reported 631 247, and moved around while I was fooling 
with it. The highest I observed was 631 268, and the lowest 631 237, so 
far. I put the top cover on to let it warm up and stabilize the 
compartment, about an hour ago, and the last look while writing, is 631 
245. It seems to move up and down by a few counts at most, with 
recurring checks.

I don't know if these kind of EFC numbers are good or bad at this point. 
I'd appreciate any advice on whether this all seems OK or not.

Ed