pdev mixers 1st look at spectrum
18sep07
A new mixer chassis for the pdev spectrometer was
installed on 18sep07. Data was taken with the red noise generator and
plotted.
The setup was:
- split the noise source and feed it to the mixer chassis.
- Use lo's of 175 and 325Mhz for the low,hi bands
- set the sample clock to 170.00384Mhz
- take 30 1 second averages. record polA, polB, and the cross
spectra U and V.
The plots show the
sampled noise spectra (.ps) (.pdf):
- Page 1: Top two plots are box 103 (hiband, low band). The bottom
2 plots are box 104. The same noise was split and sent to both boxes.
Red/Green are polA,polB. Blue/purple are stokes U,V.
- Page 2: Top The high/low spectra are overplotted from both boxes
showing the IF frequencies. The bottom plot is +/- 20 Mhz about the
center of the 4 spectra.
The large birdies are the lo's 175 and 325 leaking through the mixer.
In both cases the sampling is 170 Mhz.
- Low band: 170Mhz sampler and 175Mhz signal will appear with the
fundamental at 5 Mhz. This is seen in the low band.
- High Band: 170Mhz sampler and 325Mhz lo. This will alias in at 15
Mhz. This is the strongest birdie in the high band.
- Looks like i got the hi/low bands correct!
processing: x101/070818/testpdev1.pro
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