Thank you Larry.? Appreciate the encouragement.
Jim
Yes good idea Jim. I have voltage regulators on each calibrator voltage line, 12v, 5v, and 3.3v and I can tell you they do drift slightly over months of time. Have not charted that but might be another source of change. I have to tweak them a few hundredths or tenths of a volt every month or two but seldom more than a volt. I keep an external box fan ?on 24/7 behind the desktop JOVE computers and calibrator. I have one older Dell that the power supply is slightly under sized and it runs hot. These new NVIDIA graphic cards are power hungry. When you purchase new computers its wise, I found out, to select largest power supply available. Even more of an issue for those running laptops. With radio room ?HVAC temp control and fan for additional circulation, temp never varys in the radio room much more than two degrees. I have one experimental test equipment box I fabricated ?that's ?temperature controlled with peltier thermoelectric modules and PT100 sensitive platinum RTD temperature sensors that can regulate its metal cabinet temp to less than one degree.?
Jim your new calibrator board should be super stable.?
Larry
?
This is an outstanding line of
investigation, Jim!? Excellent idea.
--
Dave
On 3/10/25 00:47, Jim Sky wrote:
For those who have ongoing observations and working
calibrators,? I would like to ask a favor.? I want to see how
much your calibrations vary over time.? If you have the
calibrator running automatically every observation changes in
the calibration plot will probably show some "thickening"
indicating the amount of variance over several days.? Watching
that display can give some confidence that things have not
changed due to a problem in the telescope. Below is a copy of my
calibration plot for my dipole over 10 consecutive days.? It is
hard to know where this variation comes from, the receiver or
the calibrator.? My experience has been that the SDRPlay 1A
really requires an hour warmup to fully stabilize, which would
indicate some temperature dependency probably even after the
warmup.? The noise generator inside probably has some power
drift with temperature and may have some sensitivity also to
changes in it's power supply voltage. While it would be good to
sort out the source of calibration plot variation, I am mostly
interested in setting realistic error bars to our measurement.??
?
If you can, please post a screenshot of your calibration
chart (like mine below) after it has run uninterrupted for 10 or
more days.? Also I would like to have your best guess at how
much temperature variation your receiver and calibrator
experienced from night to night when the observation started.?
For example, my setup is in a partially heated room that
experienced big differences from night to night during the
period shown on the plot and I estimate it experienced about 8
degrees C from night to night.? ?I am interested in the
temperatures when the calibration was performed, not throughout
the day.? If your house has a well regulated heating system your
system might experience less than a degree of variation between
calibrations.
?
Thanks!
--
Jim Sky?
radiosky at radiosky dot com
