Occurrence of rfi versus frequency by month
last month added: aug08
Histograms of interference versus frequency are
computed
for the data acquired on the telescope using the correlator. For each
scan
of N separate integrations (typically 1 second) the rms/Mean by channel
is computed. A linear baseline is used to remove any zenith angle
dependence.
Histograms are then made of the number of
rfiCnts/TotalCnts
by frequency channel. Any rms/Mean greater than 3 times the expected
sigma
is called rfi. This sigma is computed using the bandwidth, integration
time, and corrections for: 3/9 level sampling, hanning smoothing, and
the
instrumental bandwidth of the channels. Any band passes that have more
than 80% of their channels "bad" are not included in the rfi or total
counts.
The histograms have .1 Mhz resolution. The rfi count in the .1 Mhz
channel
is incremented by 1 (and only 1) if any of the telescope channels
within
the .1 Mhz bin exceed 3 sigma.
There is a cumulative plot for the year followed
by monthly plots. Each plot has the fractional occurrence of rfi in
black.
The blue histogram is the total number of counts (nonrfi + rfi) in each
bin. The vertical scale on the right tells the total counts per bin.
The
red line is a histogram of the number of times a bandpass was rejected
because more than 80% of the frequency bins were above 3 sigma. This
histogram
has been scaled to: badcnts/(total counts + badcounts). If there are a
large fraction of red lines it may be because of some mapping programs
that include large continuum sources or have large za variations for
the
strip (some of the alfa proposals).
PLOTS OF rfi by year and month.
The entries without links have no data for that month. The 611 and 327
receiver have not been installed a large fraction of the time.
Occasionally
the rfi monitoring will take data on the receiver when it is not there
(so there is just a load connected). This depends on whether I remember
to update the receiver file to use (and that electronics reminds me
that
they have put it up or down). Sband 1800-3100 switched from just sband
narrow (2320-2420) to the full range of 1800 to 3100 sept01 when the
sband
wide receiver was reinstalled. The pattern of dips in the total counts
by bin (blue lines) is from the x111 datataking. It steps by 23 Mhz
giving
an overlap of 1 Mhz and the plotting ignores 1 Mhz from the edge (do to
filter rolloff). If you use ghostview to look at the plots, clicking on
a mouse button will blowup the region centered on the mouse.
Why to do the plots look lousy :
-
The plots are washed out with linux gv 3.5.8??
-
Turn off anti-aliasing (click on state, disable antialias)
-
I don't see all of the plot:
-
linux gv 3.5.8 .. If it says BBOx (bounding box) at the top, click on
it
and set it to letter. Push the cursor button and pan around to see
parts
of the plot that are not visible.
-
kghostview (fedora) click on view -> paper size.. select
anything
but auto (letter, or a4, or whatever..)
Year 2008 comments
- jun08: sbh,band 3450 to 4200.. pretty messy. This was a2355 doing
300 second position switching with source that had continuum. Not sure
why it looks so bad.
Year 2005 comments
mar05 - The rms for the wapp data was computed and then stored in the
old
interim correlator format back out on disc. The frequency flip was
occasionally
getting screwed up. Fixed the problem and then processesed the data
nov04
though feb05. The lbw/alfa birdies should now be in the correct
positions.
feb05 - updated exclude criteria for wapps. Some patterns were
being
included that shouldn't have been. Reprocessed the data.
Year 2004 comments
nov04 - include alfa data and wapp data for the other recievers.
feb04 - 6 to 8 Ghz (cbh) installed.
Year 2003 comments
sep03 - xband. the blocks of 25 Mhz that have rejected bands (red) is
from
the lousy pointing at xband. Some users were doing on/offs on strong
continuum
sources. The power in the on varied over the scan. When computing the
rms
by channel you got large values. Since the continuum source affect all
channels, the band got rejected (red gt 85% of channels bad)..
feb03 - telescope shutdown. drift scans 327,cband (4800) , and lbndrift.
feb03 - sbwide,lbw switch in filters while stepping. especially sbwide..
Year 2002 comments:
sep02 327 data was being taken at the wrong frequency. Was using 260IF
and trying to get 4 sub bands out of it. When the new receiver/filters
were installed in jul2002, the file x111auto.dat was not updated for
the
new bandwidths. Was corrected on 16sep02.
aug02 327
2 Mhz comb from 430 wavegu