(galfacts) reported strong rfi (lots of overflows from the mock
spectrometer) on the evening of 02nov11. The punta salinas
frequency agile radar was running in all frequencies until about 20:00
ast (it then changed to mode A 4 frequency mode). After the mode
switch, the users reported still having some trouble with rfi (although
less than before the radar moved to mode A).
A2130 used the mock spectrometers with 172 MHz bw, 4096 channels, 1
millisecond full stokes dumps.
Data from 22:35 ast was used to check the spectra.
The dynamic spectra shows one
record of data (600 ms) (.gif)
- the dynamic spectra has a time resolution of 1 millisecond.
- the pulsed radar have ipps of 1.4 to 3 millisecs.
- The horizontal axis has increasing frequency to the left.
- Some of the rfi is:
- Punta salinas
mode A 4 frequencies:
- 1258.34, 1248.9, 1242.2, and 1234.1440.
- The radar transmits two frequencies (separated by 15 MHz)
simultaneously then hops to the next pair:
- (1258,1242) and (1248,1234).
- There is also a long and short range mode.
- 1270 boriquen radar
- faa Radar 1330,1350
- Many intermods which look to line up in time with the punta
salinas 4 frequencies.
The punta salinas radar blanks their transmitter when it points at the
observatory. 65 seconds of data (1 file) was checked to see that
the blanking was still aligned with the direction of the
The plots show the total
power vs time for the 4 punta salinas mode A frequencies (.ps)
- The 4 frames are the total power vs time for the 4 punta salinas
- I took the peak channel value around each radar frequency.
- The plot shows 65 seconds of data with 1 millisecond time
resolution. The horizontal axis is label hr.hr ast.
- You can see where the power from the radar completely goes away.
- This is when they blank in our direction.
- The blanking is spaced by 12 seconds (the radar rotation
- The power levels on each side of the blanking is close to the
peak value. This tells us that the radar blanking is aligned with the
600 milliseconds of data was used to verify that the intermods (seen in
the dynamic spectra) are actually coming from the punta salinas
The plots show the total power
vs time for the punta salinas radar and the intermods (.ps)
- Page 1: avg and rms for the 600 milliseconds.
- Top; average spectra. The colors are polA,B,stokes U and V
- The vertical scale in spectrometer counts (16 bits max).
- Bottom: rms/mean for each channel.
- The puntasalinas have strong variability (probably because of
- Page 2: overplot the punta salinas pwr vs time and the intermods:
- Top: 300 seconds of data.
- black:1256,1241 frequencies transmitted together
- red: 1247.8, 1232.8 freq transmitted together
- green: 1298.6. this aligns with the black frequencies
- blue: 1289.5. this aligns with the red frequencies.
- blowup in time showing the alignment of the intermods and the
- Overflows in the fft butterfly section of the mock spectrometer
can splash radar power across the band. I checked and this record had
I looked at the number of mock overflows a2130 has had in its previous
The plot shows the number of
mock overflows by observing session (.ps)
- The vertical axis is a log scale
- the session dates were:
- So the dates were not contiguous.
- the blue dashed line is where the cals started.
- the red dashed line is the night punta salinas ran in all freq
till 20:00 ast
- If i throw out the data prior to 20:00 for this date, there are
about 500 overflows. This is similar to other nights. So the observers
comment about continued problems after the modeA switch was not
something different from other nights.
- There is a large variation in the overflow errors vs observing
- They are covering the same za range (except the cals add more
counts in a few regions).
- The scattering of rfi into the dome is za dependent (geometry)
with much more getting in at some narrow za ranges.
- The radars have 12 second rotations.
- The variation in counts by session may be the beating of
when the dome was at certain za's vs when the radar pointed at
- punta salinas radar ran in all frequencies for the first part
(till 20:00 ast) of the a2130 run on 02nov11.
- They then moved to mode A.
- mock spectrometer overflows continued as well as birdies
appearing at frequencies other than the standard radar
- Looking at the dynamic spectra and the plots, many of these
birdies were being created (probably in our system) by the punta
- The blanking of the punta salinas transmitter was working
correctly during this period.
- Looking at the mock spectrometer overflow errors, they were
grouped in time. This was probably a geometric affect (the dome was
moving from 2 to 20 degs za).
- The faa radar was also running during this time..
- Excluding the mock overflows before the radar went to mode A,
02nov11 session overflows was similar to other nights.
- There is a large variation in overflows by observing session.
This may be a beating of the dome being at a particular postion and the
12 second rotation period of the radar.