[time-nuts] 5370B arrived - any FAQ

Jim Palfreyman jim77742 at gmail.com
Thu Jun 19 03:08:29 EDT 2008

Hi Folks,

Well my 5370B purchased off ebay arrived from the US in perfect
condition. It passed all the operator checks (all well within spec)
and the only issue being that the internal 10811 oscillator was
running a tad slow. A quarter of a turn with the screwdriver fixed

Having played with it for a day or so I have a few questions. I was
wondering if there was an FAQ anywhere?

My first issue was powering it up. It said on the socket on the back
110-240V and I nearly just plugged it in out of habit (as you can do
with modern power supplies). I decided to read the manual, however and
was so glad I did. 240V into it without flipping the little board over
and changing the fuse would have been a disaster! I didn't have a 1.25
amp fuse but a 1 amp worked ok.

Second issue was opening the cover! It wasn't in the manual and I
couldn't find it anywhere on the net. I figured it out in the end
(undo the screw at top rear and remove the top two feet and slide the
top back). My top didn't slide easily and so it wasn't obvious.

My third issue I'm not sure how it happened and I think it was a bug.
After lots of prior fiddling I started taking measurements between two
1 PPS readings from two different GPSDOs (Thunderbolt and Z3815A) and
it was telling me the difference was 980 nsec. Checking the waveforms
on an oscilloscope said it should have been of the order of 3 nsec.
This had me stumped for ages until I clicked the DSP REF button and it
showed -977! This was obviously from previous fiddling but I thought
the SET REF button would be lit if REFERENCE was non zero. I haven't
been able to repeat this. Any ideas? Motto here is always click CLR
REF to be sure.

Another thing I don't understand is to do with frequency measurements.
Gating with 0.01, 0.1 or 1 second gives good results for a reference
10 MHz, but why does measuring the same frequency with the 1 PERIOD
set and say 1000 samples not give good results?

Thanks in advance,


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