Measured Intermods in ALFA/pdev from radars.

03may05

Links:

Intro
Setup for data taken 30apr09
Plots of the measured intermods
Summary
Table of mixer intermods

 

Intro:

   The radar rfi seen in the a2133  data during apr09 showed radar like rfi (time periodicity that was synchronized to the radars) spaced over parts of the band.

    The intermods in the 1st and 2nd (base band) mixers were then computed for intermod orders of 1 to 10. The standard alfa/pdev search setup of 1375 SkyCfr, 1300,1450 subband centers was used.


The setup for data taken 30apr09.



Plots of the 30apr09 intermods:

    The rms/mean by channel was computed for the 600 spectra (60 secs of .1 sec spectra) of each scan.  These  rms/means were then overplotted using the same color for each beam of alfa (6 beams overplotted.. only polB was used to make the plot files smaller). This was repeated for the 6 frequency settings (1375-170). Each frequency plot was offset for display purposes and plotted with a different color.  The rdr like rfi will have larger rms/means.

1450 Mhz Band (.ps) (.pdf)
1450 Mhz Band. Blowup around rfi (.ps) (.pdf):
1300 Mhz Band. (.ps) (.pdf):


04may09 . step 2nd lo by 1 Mhz.

    On 04may09 data was taken with alfa and the mock spectrometers. The setup was:

SUMMARY:


Alfa/pdev mixer intermods in the 1450 Mhz band (rf center freq=1375)
Radar
Intermod
sky Freq
time
correlation
intermod paths

FAA
1330/
1350
1475
yes
rfi lo         
result
mixer
 5*1330 -4*1625
150 IF1
1
-2*275(1350)  3*175
-25 baseband
2
 5*275(1350) -8*175 -25 baseband
2
1480
yes
rfi             
lo           result        
mixer
-6*1330  5*1625 145 IF1
1
1375
yes
rfi      lo         
result       
mixer
5*1350
-4*1625
250 IF1
1
5*295(1330) -8*175
75 baseband
2
2*275(1350)
-1*175
75 baseband
2
6*275(1350)
-9*175
75 baseband
2




Remy Radar
1270/1290
1422 (1269.5)
yes
rfi              lo result         mixer
4*1269.5 -3*1625 203
1




Areostat radar
1261.25,1246.2
1256.5,1241.74
1399
1246.2 looked closer
to 1246.7
yes
rfi           
lo       
result      
mixer
8*1246.7
-6*1625
223
1


processing: x101/090426/rfichk.pro

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