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: http://www.naic.edu/~phil/rfi/430/large419/large419birdie.html
Дата изменения: Thu Feb 5 21:24:19 2009 Дата индексирования: Sat Oct 17 13:59:03 2009 Кодировка: Поисковые слова: heart nebula |
Page 1 Top 5 minute averages: 30 5 minute spectral averages are over plotted. Black is polA, red is polB (the feed is circular). The birdie was not resolved in the 24 Khz channel widths (after hanning smoothing). The amplitude of the birdie averaged over 5 minutes got up to about 12000 times Tsys. Since the birdie was not on all the time, the actual strength was greater (see below). Page 1 Bottom. the strength of the birdie: the single birdie channel (averaged over 5 minutes) is plotted vs time. It reached a peak during the 5 minute average at 14.36 (14:21 ast). Page 2 top. birdie channel strength with 1 sec resolution: This plots the 24 Khz channel at 419.2 Mhz vs time with 1 second resolution. The vertical scale is now db's above Tsys. The constant value of 50 db probably means that the system was saturated. The slow rise of Tsys around the green dashed line is the galaxy passing through the beam. Page 2 bottom how long did the birdie stay on. This plot shows how long the birdie stayed on (using the 1 second sampling). The most common duration was 3 seconds. At 14.3 hours it stayed on for 25 seconds at a time.
Base band data with 100 Khz bandwidth was taken after the 1 second data above. The spectra were computed using 100 Hz resolution (1K transforms). This gave a new spectra every 10 milliseconds.Top a 1 second spectra. Black in polA and red is polB. The dashed green line is at 418.625 Mhz. The birdie has not been resolved in the 48 Khz channel. For some reason polA is a lot stronger than polB (even though the main beam of the feed is circular). Middle the time variation of the birdie. This shows the 48 Khz channel at 418.625 Mhz vs time (with 1 second resolution). The birdie gets up to about 7000 times Tsys. Bottom how long the birdie stayed on. This shows how long the birdie stayed on vs time. The most common duration was 3 seconds.
The final plot shows the birdie spectra averaged over a single pulse when the modulation was on and when it was off (.ps) (.pdf):The birdie turned on twice in the 10 seconds. The ghost at 418.75 is probably instrumental. The birdie has a carrier and then a modulation phase. Some of the properties are:
- The birdie is on for 2.07 seconds.
- The modulation is on for .53 seconds
- The birdies are spaced by 5.55 seconds. This is a little different than the 1 second data.
- It does not look like this system was going into saturation during this time. The data was taken through the radar interface with a 12 bit a/d converter (the 1 second averaged data used the 9 level correlator).
The black trace is averaged over 50 milliseconds when the modulation was on. The red trace was averaged over 67 milliseconds when the modulation was off. The vertical scale is db's above Tsys. It got up to about 50 Db (being on during the entire time). It is about 2.4 Khz when the modulation is off and 9 Khz when the modulation is on. This data was probably not saturated.
processing: x101/061201/chk430.pro riraw430.pro, x101/061206/chkrfi.proA birdie at 419.2 Mhz was seen on 06dec06.
- The birdie was not resolved with a 24 Khz channel width.
- Within a 1 second spectra the strength got up to 50 db above Tsys ( in a 24 Khz channel width).
- The receiver system (using the interim correlator saturated during the birdie).
- The birdie was intermittent. It would stay on for about 3 seconds (using 1 second sampling).
- This was the only day it was seen.
A birdie at 418.625 Mhz was seen on 01dec06. Data was taken with 1 second and 10 usecond resolution.
- The birdie had a period of 5.55 seconds. It would turn on for 2.07 seconds. It would modulate for .53 seconds.
- The unmodulated biridie has a bandwidth of 2.4 Khz
- The modulated birdie has a bandwidth of 9 Khz.
- The birdie got to be about 50 db above Tsys in the 100 Hz channel width.
It may be that these are the same birdie. It would be nice to get some base band data of the 419.2 Mhz birdie to compare it with the 418.625 birdie. Neither of these birdies have shown up in the x111 rfi monitoring data. It uses the 422-442 Mhz filter, but we can still see other birdies in this region.