Intro
On 02nov22 around 10am power to the cal fiber
box in the 12meter pedestal was accidentally disconnected. The
power was reconnected on 04nov22 around 10am. During this
period, the cal did not fire (no drive signal). Pulsar
observations also showed a large amount of interference in the
folded pulsar period.
Setup:
I looked at the file
sspsr.20221103.B0329+54.b0s1g0.00100.fits. This was the first
dataf ile after the cal scan.
The setup was:
- telescope position: az=7.84, el=36.84
- iflo:cfr 2278 MHz.
- mock data taking:
- 256 channels, 172.032MHz bw
- sample time: 0.0001994047 secs
The data
dynamic spectra were made from the first 1 second of data (.2
ms sampling)
- PolA
dynamic spectra (.gif)
- There might be a little 60 Hz around 2248 MHz
- PolB
dyamic spectra (.gif)
- There is a darker line across the entire band
every about 8 milliseconds
- This is normally from saturation somewhere in the
receiver chain.
- It is synchronized to the 60 Hz signal seen at 2312MHz.
The plots look at the total power vs
time for the first second of data (.ps) (.pdf)
- Page 1: total power vs time
- top: 1 second of data
- Bottom: blowup in time
- You can see the negative going spikes in polB.
- They are spaced by .00832 sec or 120.Hz (with 1 sec of
data we only have 1 Hz resolution).
- the compression is 20%
- PolA looks normal
- Page 2: magnitude of total power spectra
(abs(fft(tp/mean(tp)))
- Top: polA
- there is a small 60 Hz signal
- bottom: polB
- The comb is at 120Hz. it is about 5% of Tsys.
Summary
- The power to the cal fiber box in the 12meter
pedestal was accidentally disconnected 02nov22 10am until
04nov22 10:am
- during this time, no cals were fired.
- Pulsar data taken while it was disconnected showed a 120
Hz broadband saturation in polB
- checking the data before the box was unplugged, and
after the box was plugged back in, no 120 hz saturation
was seen.
- This may have something to do with the 60Hz signal that
we've seen in polB at selected frequencies.
processing: x101/221104/sbnocal.pro
