lna polA stage 2 current glitches seen in
IPS (InterPlanetaryScintillation) is taking
data with the 327 receiver and the mock spectrometer. The
- Dump 50 MHz spectra every 2 milliseconds. Do this for 180
- Split the spectra into 5 10MHz bands.
- remove the rfi and the compute the total power for each 2 ms
- Compute the spectra of the total power time series taking 10
seconds of data at a time (.1 Hz resolution)
- We end up with 18 10 second spectra for each of the
5 10mhz bands
- Then take the average and the median spectra over the 18
spectra and then over the 5 10mhz bands.
A movie was made showing the spectra of
the total power for the 327 receiver data on 11may20
- the best way to view the move is with mpv.. mpv --loop
- each frame contains:
- left column : polA
- middle column: polB
- top row (col 1,2): average the 18 spectra
- bottom row(col 1,1): median of the 18 spectra
- right col, top: average and median of all bands, all
- This also includes the time (ast) for the start of the 3
- bad frames:
- 3 : 15:09
- 5: 15:27
- 7: 15:51 .. the worst
- 8: 16:02 .. the 2nd worst
- You can see the large powers at the right of the band for
polA.. polb is also affected a little
The plot shows the bias currents for
327 stage 1 and 2 for 11may20 afternoon (.ps) (.pdf)
- The top two frames are stage 1 polA and polB
- The bottom two frames are stage2 polA and polB
- The vertical lines show the start of each 3 minute observation
from the movie
- the solid line is the start
- the dashed line is the end of the 3 minute scan
- Green lines are frames(scans) in the movie that did not have
the high freq power
- the red lines have the high frequency power
- the purple line is intermediate.. it had a few small bumps
- The worst 2 red scans around 16:00 are when polA stage 2
current was jumping around the most.
- Note that the current is only moving by .01 or .02 milliamps..
- polA stage 2 bias current is jumping around causing 30-120+ Hz
power variations in the sampled data.
- this is affecting the ips measurements being taken during the
covid19 down time.
- It will also cause problems with the p1693 pulsar search.
- There has been a recurring set of intermittent glitches
in the 327 receiver (for over a year). it would come for a few
minutes and then go away.
- I wonder if the could be causing it?