180212 100ms rfi
12feb18 showed 100ms periodic rfi spanning 2388-2390 MHz.
- Data was taken with the mock spectrometer using 4096
channels and 2.048 ms spectral dumps
- 5 scans were taken:
- file 300: sbn: cfr 2390 MHz, bw=20MHz, 750nb mixer, 16
bit sampling, 67 seconds of data
- file 500: sbn: cfr 2380 MHz, bw=40MHz, 750nb mixer, 32
- file 600: sbn: cfr 2380 MHz, bw=80MHz, 750nb mixer, 32
- file 700: sbw:cfr 2380 MHz, bw=80 MHz, 750nb mixer, 32
bit sampling, 2040 to 2400 rf filter
- file 800: sbw: cfr 2380 MHz, bw=80 MHz, 750
mixer, 32 bit sampling, 2040 to 2400 rf filter
dynamic spectra were made using 485 spectra (.99238
secs) of data
|300, sbn 2390MHz,bw 20mhz
|500, sbn 2380 MHz,bw 40 MHz
|600, sbn 2380 MHz, bw 80MHz
|700, sbw 2380 MHz, bw 80MHz
|800, sbw 2380 MHz , bw 80MHz, 750mixer
- The rfi was seen in sbn and sbw.
The images show polA (which was stronger than polB)
- Some of the spectra is more cut off at the higher end
because of the filters.
- The period looks close to 100 ms.
Plots of spectra
at 100 ms peak (.ps) (.pdf)
- The 5 frames are the 5 separate files
- Each frame holds a 2.048 ms spectra when the 100 ms rfi
- the first frame (file 300) saturated. it only used 16
bit spectra. The other 4 spectra used 32 bit spectra.
- The 3 colors are 3 spectra around the peak:
- black: 2.048 ms before peak
- red : at peak
- green: 2.048 ms after peak.
- The spectra have been normalized to the spectral band
Spectra of the total
power 2389-2398 MHz (.ps) (.pdf)
- For each file, the total power between 2389 and 2398
MHz was computed.
- the magnitude of the tp spectra was then plotted
- A comb of harmonics is show going out to about 240 hz
- Black is polA, red is polB.
- The first file had 67 seconds of data, the other 4 files
had less data.
- for file 300, the 24th harmonic was measured to be 234.372
- dividing by 24 gives the fundamental as 9.7655Hz (period
- So the period is not exactly 100 ms.
- periodic rfi was seen with sbn and sbw
- the period was .1024 seconds