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

On Mar 10, 2025, at 1:10?AM, Dave Typinski via <davetyp=[email protected]> wrote:

?

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.

?

<mime-attachment.png>

Thanks!

--

Jim Sky?
radiosky at radiosky dot com

Thank you Larry.? Appreciate the encouragement.

On Mon, Mar 10, 2025 at 3:25?AM Larry Dodd via <101science=[email protected]> wrote:

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

On Mar 10, 2025, at 1:10?AM, Dave Typinski via <davetyp=[email protected]> wrote:

?

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.

?

<mime-attachment.png>

Thanks!

--

Jim Sky?
radiosky at radiosky dot com

Jim,

?

I'll look into your question as soon as I can. My RJ station is operated remotely, and I'm waiting for a few warmer days to head out.

?

First of all: I've already had trouble deriving a stable calibration temperature from the measurements with the Noise Source Characterizer. I may have a malfunctioning noise source.

Therefore, I always add the background temperature to the measured signal temperature in my images to obtain something like a signal-to-noise ratio.

?

Sabine

--

Germany
Standard time: UTC +1 hour