Hi Pete, Are you really at an altitude of 645 meters ? Also, it seems that your oscillator gain (currently at -5 Hz/v) may not be set right ? Have you checked the power supply voltages and observed them on an oscilloscope to see if they are relatively clean and free of spurious junk ? The available number of SATS is quite low and could be a matter of concern. Bill....WB6BNQ Pete Stephenson wrote: >On 12/15/2016 7:45 PM, Charles Steinmetz wrote: > > >>Tom wrote: >> >> >> >>>There's something very odd going on here, either with Pete's TBolt, >>>and/or with Mark's Heather v5. >>> >>>2) It also shows some truly erratic behavior the last day and a half, >>>with multiple, massive, sudden temperature drops going down several >>>degrees. I've never seen this. >>> >>> >>I think the more revealing trace is the DAC voltage. There are ~70mV >>plunges, to a dead quiet (at this scale), more negative value. 70mV is >>huge, corresponding to a -35e-9 frequency shift (350mHz). If the DAC >>voltage actually changed that much, it would pull the OCXO so far off >>frequency during these events that it would take much, much longer than >>shown (indeed, much longer than the width of these events) to >>re-stabilize. Yet we see clean jumps within seconds, and no settling. >>(Unfortunately, the Tbolt's estimation of frequency is not plotted on >>the posted screen shot.) >> >> > >Apologies, I did have the frequency plot turned off. I've taken some >more screenshots with the frequency plot turned on. > >screenshot.png is a close-up of one of the odd spikes, while >screenshot2.png took place ~10 minutes later (I just scrolled to the right). > >The small frequency jumps in screenshot2.png are due to satellites >entering and leaving the field of view. Due to the setup of my >apartment, the antenna location is decidedly sub-optimal and has a clear >view only to the northwest. > > > >>I find it hard to believe that LH does much processing of the reported >>DAC voltage, so I think it's safe to say (1) the LH plot shows >>accurately what the Tbolt is reporting (at least WRT the DAC voltage), >>and (2) the actual DAC voltage is not doing what the Tbolt is reporting. >> >>Looks like a sick Tbolt to me. >> >> > >Any idea what might be the issue? I can do SMT rework to replace a bad >temperature sensor or other faulty chips, within reason (super-fine >pitch stuff is a pain). > >Cheers! >-Pete > > > >>Best regards, >> >>Charles >> >> >>_______________________________________________ >>time-nuts mailing list -- time-nuts@febo.com >>To unsubscribe, go to >>https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>and follow the instructions there. >> >> > > > > > ------------------------------------------------------------------------ > > > ------------------------------------------------------------------------ > >------------------------------------------------------------------------ > >_______________________________________________ >time-nuts mailing list -- time-nuts@febo.com >To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >and follow the instructions there. >

On 12/16/2016 1:54 PM, wb6bnq wrote: > Hi Pete, > > Are you really at an altitude of 645 meters ? Yes. That's the result of multiple surveys over a week a year or two ago. I'm pretty sure the altitude hasn't changed since then. :) I think Lady Heather shows the altitude as that above the WGS84 geoid rather than above sea level, right? I'm trying to resolve some discrepancies in reported altitude between my handheld Garmin eTrex 20, Oncore UT+, and Thunderbolt (the Oncore and Thunderbolt share a split signal from the same antenna). > Also, it seems that your oscillator gain (currently at -5 Hz/v) may not > be set right ? That's the default for the Thunderbolt. I've tried tuning it a bit to other values but it runs reasonably well at that value so I stick with it. > Have you checked the power supply voltages and observed them on an > oscilloscope to see if they are relatively clean and free of spurious > junk ? I've checked them with a multimeter and, while not dead-on at +5, +12, and -12V, they're within the acceptable range mentioned in the Thunderbolt manual. I have an oscilloscope and will probe them later today when I get home from work. > The available number of SATS is quite low and could be a matter of > concern. The antenna is in a poor location, facing to the northwest. It's the best I can do in this apartment, and the number of satellites seen is typical for this location. What's interesting is that the weird transients would occur at least once every few hours over the last two days, but when I switched to using a hardware serial port (as opposed to a genuine FTDI USB-to-serial adapter connected to a hub) there hasn't been anything for the last 7 hours. I made no other changes to the setup. The adapter had been working fine with no issues for at least a year and I was using it for other devices as well with no problems. I had turned off the Thunderbolt for a few months to save electricity (with my PhD studies nearing a close I needed to focus and take time off from amateur radio stuff) and just turned it on again in preparation for the leap second. It's possible this may have simply been a communication error between the Thunderbolt and the computer. I'll do more tests to find out. Cheers! -Pete