during the platform beam repair (16mar10) showed rfi coming from the
head. The setup was:
- lband wide receiver in linear pol mode
- mock spectrometer using 4 boxes to cover all of lband.
- .1 second dumps, 21 Khz resolution, full stokes data taken,
8192 channels/172.032 Mhz
- Data was taken from 16:42 16mar10 to 07:41 17mar10 ast.
- The telescope was sitting at az=296.4, za=8.
Plots/images were made of the cross head rfi using the band centered at
1350 MHz. This band included some of the most regular occurences of the
cross head rfi (1317, 1400). Other frequency bands in the lbw reciever
also showed this rfi.
spectra showing cross head rfi (.gif):
- Top: polA, bottom: polB
- Each dynamic spectra shows 250 seconds of data (2250 .1 second
- The cross head rfi appears at:
- 1318 MHz and 1398. MHz
- PolB has a wider rfi range at 1398 than polA.
The plots show the
frequency of the total power variations for the rfi frequency ranges
- Page 1:
- A total power time series was computed for 4 MHz about
1400 MHz and 1317.7.
- The transform contained 2250 .1 sec time samples.
- The power spectrum was then computed for each of these time
- Top: 1400 MHz power series spectra
- bottom: 1317.7 MHz power series spectra
- Black is polA, red id polB
- Multiples of 1.2 Hz has been flagged in green.
- The crosshead rfi is stronger in polA than in polB.
- Page 2: Average spectra (225 secs) for the data used.
- The resonances in the lbw feed near 1400 MHz are flagged in
blue (polB) and green(polA).
- These are very close to the frequency for the cross head rfi.
- 1317.7 (the center of the other cross head frequency band is
- There may be a small bump in polA above this frequency. Could
this also be a resonance?
- Rfi at 1.2 Hz is seen in the lbw receiver.
- The rfi was most often seen around 1317 and 1400 MHz. It was also
seen in other frequencies of the receiver.
- The 1400 MHz rfi is very close to known resonances in the lbw