Tue., Apr. 24th

I want to spend some time today trying to prioritize a list of things to accomplish before I leave for China.  I'm leaving May 4th, so that gives me 8 work days between now and then (including today) to get stuff done.  Here are some work items I can think of:

1. Ray requests an operating manual.  That should not take very long.  However, I want to do it last, so it can reflect the most up-to-date state of things.
2. I would like to do at least one example of a module that actually provides interactive real-time graphs of some meaningful data - e.g. the discrepancies between the intervals between subsequent PPS pulses and the nominal second defined by the OCXO reference (10M OCXO cycles, or 750M PLL cycles).  That way, if someone wants to pick up from there, and do some more graphs, they will have a model to use as a starting point.
3. Figure out the configuration of the GPS antenna cable and order the components we need for that, and work with Reed Lambdin to plan out the route that the cable will take.  First step:  Try to figure out how much attenuation the GPS module can tolerate while still receiving satellites.
4. Someone (not necessarily me) needs to solder the SMA connectors to the FEDM at some point before it is physically installed at CLC.  The FEDM should be re-tested afterwards.
5. Someone (not necessarily me) needs to go through the Quartus design that Juan and Michael Dean were working on, and identify whether it really implements the same logic as the previous version of the high-speed components - it seems to me that it can't, or else the Fmax would be the same.  One thing:  The XORs can be moved out; although that shouldn't really affect it.  We should also go through the compilation settings side-by-side and compare them with the baseline project (the one on Q:\).  Darryl expressed some interest in helping with them.
6. At some point, someone (not necessarily me) should figure out what is a reasonable voltage level to operate the thermoelectric plate at, and we should rig up a power supply for it.  Goal:  Keep FPGA package surface close to (but not below) the maximum indoor dew point in the classroom.  According to Wikipedia, a dewpoint of 13-16 C is "comfortable."  So 16 C might be a good guess.  But to be safe, we should probably measure the actual dewpoint in the classroom.  The dewpoint can be calculated from the temperature and relative humidity.  Cheap hand-held digital meters capable of measuring this information can be purchased at outdoor/sporting goods stores.  Maybe I'll pick one up on my way home.
7. At some point before we install, someone (not necessarily me) should fasten down more of the loose cables/connectors on the electronics platform.  Some of this has to wait until the SMA connectors are soldered.  The power cable needs holes drilled thru the board to run a heavy-duty cable tie through.
8. At some point, someone (not necessarily me) should cut the ventilation hole(s) and wiring hole(s) in the plastic enclosure.  Alternatively, someone also suggested that holes could be drilled in the platform for routing some (or all) of the cables - this might provide a neater look.  I think a circular saw hole (about 1" diameter) near the center of the platform would provide relatively easy access for all of the cables we'll need.  Here's a list of all these:
   • Main AC power cord for the ATX supply.  (This is the only power input, assuming here that we can also power the thermoelectric cooler through Samad's board.)
   • GPS antenna cable, snaking in from some long pathway coming down from the rooftop.
   • Bundle of 3 coax cables and 3 power cables (speaker wire), these to split out in pairs (one coax cable +  one speaker cable) to enter 3 conduits fanning out to the 3 detectors.
9. At some point soon, someone (not necessarily me) should construct the power cables for running the 12V power to the detectors.  Ray got the barrel connectors, so they just need to be soldered to one end of the speaker wire (cut to ~40' lengths), and for the other end, we still need to rig up some kind of connection for plugging into Samad's board.  Maybe yellow (+12V) and green (GND) jumper wires?  -  OK, I went ahead and pulled out three yellow/green pairs from the power supply board, each to a 2-pin male header - one end of the speaker wire can be soldered to this.  On the speaker cables, let's use white = +12V, copper (clear) = ground.
10. The new OCXO board (designed by David & Samad last week) needs to be "taped out" to CAM files (show David/Samad how to do this), and submitted to Sunstone for fabrication.  We have solder paste and a hot-air gun which should be suitable for the soldering the SMT OCXO parts, which are on order.  We have the other parts needed (male 2-pin header, and right-angle SMA connector) so we should be able to complete assembly as soon as the fabbed boards and the OCXO get in.
11. Empirically (using waveform generator and scope) measure signal propagation delays down the 3 main coaxial cables we're using.  This is important for reducing systematic error in our measurements of the relative arrival times of pulses at the 3 detectors, and also for reducing systematic error in our measurements of the absolute arrival times of pulses (i.e., arrival times relative to the GPS reference).  This should be easy, I have everything I need for it - signal generator, scope, and coax splitter.  Oops, no, correction:  I really first need an SMA-to-BNC adapter of the right type.  (SMA female to BNC male.)  The one we have is the other type.  [ ] Look for this at Radio Shack.

The "La Crosse Technology
Indoor Comfort Level Station"

I went out shopping for a hygrometer.  After striking out at Kevin's and Trail and Ski, at Lowe's I found a nice little digital combination thermometer/hygrometer for $20.  Tried it at home just now; got a temperature of 24.3 C (75.74 F) and a relative humidity of 44%.  Found a little iPhone app called DewPoint that calculates the dew point temperature from this data - it says the dew point is 11 C.

Let's try checking this figure against the approximate dew point formula on Wikipedia:  http://en.wikipedia.org/wiki/Dew_point#Calculating_the_dew_point.  Made a spreadsheet Dewpoint.ods (in my FAMU/COSMICi Dropbox) to perform that calculation.  Using the same inputs, it gives 11.256 degrees Celsius, suggesting that the little iPhone app and the Wikipedia formula are both reasonably accurate, or at least about equally inaccurate.  :)  Probably the app is rounding.

OK, now I  just need to bring this little measurement box into CLC, hold it up near the ceiling where the electronics platform will be, run the calculation in the app, and then we will have a baseline estimate for what the "typical" dewpoint at that location may be.  To get a clear idea of the maximum dewpoint, we'd probably need to take a lot more measurements at all different times of day/night, different seasons, different outdoor weather conditions (humidity, etc.).  This is a prohibitive amount of work (unless we set up some kind of automated data collection, which also is a lot of work), so instead, we should probably just take a few measurements and add a slop factor (safety margin).  Anyway, one would hope that the building's climate control system normally succeeds at keeping the humidity at a reasonably low level.  Not necessarily a very good assumption, but perhaps a reasonable starting point.