[time-nuts] Newbie question about thunderbolts

[James Tucker]

Hi, Paul. Glad to see you made it here. For the time-nuts; Paul and I
have spoken about these issues, and I have had similar experience. The
only thing I would add is the the spikes to seem to occur less
frequently with a better antenna placement, but when they start to
cluster, they fire off one every two or three seconds, sometimes
faster.

JimT

On Wed, Feb 27, 2013 at 2:08 PM, Paul Berger <phb.hfx at gmail.com> wrote:
>
> Hello all:
>
> I am an electronic technician with 30+ years experience fixing
> computers.   In my spare time I like to play with old computers and
> electronics.  Recently I got bit by the precision timing bug, partially
> after running across the wonderful leapsecond.com site, which lead me
> here.   First I got  a FE-5680A, then after reading some of the archives
> here I bought a Nortel / Trimble 45000   GPSDO and still later a used
> Thunderbolt-E.
>
> My main interest in these devices at this time is for a accurate bench
> top frequency source, however I do have a 59309A running off of each of
> the GPSDOs.  I am wondering if they will drift apart, but I suspect I
> will need to wait a long time to see evidence of that. I set them
> simultaneously by setting them both to the same GPIB address and
> connecting them to the same bus on my HP-86B, this works well for
> setting them but I have to remember to disconnect one or change the
> address on one before I try to read them.
>
> MY question concerns the thunderbolt-E, I have been using LH to monitor
> both of the GPSDOs and was quite surprised to see that the Nortel 45000
> seems to perform much better than the thunderbolt-E, I thought that the
> E being a newer device it would perform better.  I will admit that I
> have a much less than ideal antenna setup however the antenna location
> is the same for both devices, they are  only a couple feet apart.  The
> antenna's are a Trimble magnet mount antenna and a the dome antenna that
> came with the thunderbolt-E kit. Initially I had the magnet mount
> attached to the Nortel and the dome antenna attached to the E, but I
> have now swapped antennas but it has not made any difference , and I am
> beginning to wonder if my E is in fact defective.  I have been in
> contact with one other person who has an E and his experiences have been
> similar to mine, even though he has a much better antenna setup, so I
> would like to ask if there is anyone else out there with an E, and ask
> the group for comments on what I am seeing.
>
> My observations have been that the 10MHz is not very stable, on LH I
> will see relatively large spikes  in the DAC voltage that of course
> impacts the 10MHZ, I had it connected to my 5316A counter that was
> running with the FE-5680A as a timebase, with a 10 second gate time and
> logging counts with my 86B and I was seeing excursions og over 100Hz
> which I guess percentage wise is not huge but I do not see anything like
> that on the Nortel.  Now some of these excursions do occur when there
> are satellite switches, and if they all occurred coincident to satellite
> switches I would mark it up to my crummy antenna arrangement, but they
> don't they occur even when the satellite tracking is stable and often
> come in groups of several transition first positive followed by an equal
> transition in the negative direction.     There is also a constant
> chatter of about 100uV on the DAC line as reported by LH which also
> translates to noise on the OSC and PPS lines, my technician sense thinks
> that looks like power supply noise, but I have not looked under the hood
> yet.   One really annoying thing I have noticed is the E reports having
> saved my location, however it apparently has not so every time it resets
> for whatever reason it goes into a self survey, which because of my less
> than ideal antenna setup usually takes some time to complete, even a
> warm reset resulted in it losing it location and entering self survey.
>
>
>
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