Correct rcvr gain variations with winking cal.

How to correct the gain variations
How the noise is affected.
Processing the data
Plotting the data


   Monitoring the 12meter total power has shown that it varies. As the temperature increases the total power goes down.

On 8nov21 a peltier cooler was installed to temperature stabilize the cal diode. If the cal diode output is constant, then it can be used to correct for gain variations in the system (as long as the gain variations are slower than the 25Hz cal).

On 17jan22 2 minutes of data was taken with the winking cal. The winking cal was then used to correct for gain variations (more info)

On 16mar22 15 minutes of data was taken with the winking cal to see how far (in integration time) we could extend the correction. The results are reported below.


The analysis used the 25Hz hardware winking cal data taken on 16mar22. The setup was:

How to correct for gain variations

    The hardware cycles at 40ms (20ms on ,20ms off). It can be used to correct for slow gain variations in the electronics.


What the correction does to the noise statistics

    Dividing the tpOff (tsys) by the cal deflection will increase the rms noise level.

    To not blow up the errors so much we can:


Processing the data.

    For freq band of 900 seconds of data:

Looking at the results:

Uncorrected total power calOff vs time (.ps) (.pdf)

Over plot tpCaloff for the 7 freq bands (.ps) (.pdf)

Over plot tpOff  with and without corrections (.ps) (.pdf)

Divide TpOff by a polynomial fit to tpCal and then compute the measured rms. Compare with no correction.(.ps)  (.pdf)

Using tpOff/tpCal plot the rms/mean for  different integration times (.ps) (.pdf)

Break the 155MHz band into 25MHz sections to see if any rfi affects things (.ps) (.pdf)


processing: x101/220316/

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