The xband receiver on the p12m telescope
was monitored for 19 hours on 21may21. The setup was:

- 16:20:28 21may21 to 11:09 22may21 AST
- telescope sitting at Az=0 el=75.

- xband receiver using 8050 to 9200 MHz
- Mock spectrometer used to record the data.
- 7 172 MHz bands centered at:

- 8132,8296,8460,8624,8788,8952,9116
- Each band spaced by 164 MHz
- 2 pols, 4096 channels/pol, 42 KHz channel width
- spectra dumped once a second

- When computing the total power, frequency channels with rfi were rejected:
- compute rms/mean for each freq channels.

- do a linear fit to the rms vs freq and reject any channels with fit residuals > 3 sigma.
- the rfi rejection was not very helpful. We had 19
hours of data with the mean value varying with temp. The
rms/chan was large so clipping at 3 sigma left a lot of
rfi.

- the total power for each 1 second spectra was then computed over the good channels (scaling by the channels used).
- The first and last bands were only partially filled with rf power. They were cutoff by the p12m rf bandpass filter. In these cases only the part of the band with power was used for the computation.
- The total power vs time for each frequency band was
normalized to the average of the first 1000 points
taken (so the units become Tsys).

The total power vs time for the
entire 19 hour session was plotted:

The
total power vs hour of day with temp (.ps)
(.pdf)

- The x axis is hours since the start of 21may21 (so hr 30
is 6am 22may21)

- Top
- over plot total power vs hour of day for the 7 polA bands
- there were several jumps up and then back down. The
amplitude of the jumps looks like a function of the
frequency band.

- Middle:

- over plot total power vs hour of day for the 7 polB bands.
- There was some wandering around at midnite. It recovered and then started anew around 29 hours (5am).
- The amplitude also looks to be a function of the
frequency band (higher freq moved more).

- Bottom: pedestal temperature
- The pedestal temperature (behind the postamp chassis) was recorded once a minute.

Total power vs temperature (.ps) (.pdf)

- Top: median (over the 7 freq bands) total power vs hour of day.
- The green curve is the temperature over plotted on the curve (scaled to fit)
- Bottom: linear fit total power vs temp.
- solid lines: total power vs temp
- dashed lines: linear fit
- black polA, red polB

- The coef:
- tpA=3.44 - .0277*tempF
- tpB=2.43 - .0166*TempF

- The total power units are Tsys.
- So the electronic gain must be changing by 2.7 and 1.7 % per deg F

Total
power vs Right Ascension (.ps) (.pdf)

- Top: PolA total power vs ra
- Bottom: polB total power vs ra
- the dashed red line is the galactic plane.

total power vs time blowup
(.pdf)

- The total power vs time is plotted in 1 hour blocks.
- polA 1st and 3rd frames
- polB 2nd and 4th frames.
- The 7 bands for each pol are over plotted.
- Each 1 hour plot is normalized to unity.
- some jumps
- I've excluded the polB drifting. this lasted for hours.
- there were 3 polA jumps.

- The power increased with the the amplitude a function of frequency.
- After awhile the level returned to that before the jump
- After the final jump up, it stayed that way till the end.
- polB bands diverged around 24 hours, again the amplitude was a function of freq band. It eventually came back.
- at 28hours they diverged again and remained separate.

- The electronic gain dependence with temperature :
- -2.8%/degF polA
- -1.7%/degF polB
- PolA had 3 sharp jumps where the amplitude was a function of freq band. Each time the came back to the prejump levels.
- the final jump remained for 12 hours.

- Pol B drifted by up to 10% over 7 hours.
- The amplitude of the drift was a function of the band
frequency. Higher freq drifted more.

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