Baseband sampled data with the ri.

Baseband sampled data was taken on 03may07 and 04may07 using the ri (12 bit a/d's) the setups were:

date	rfCfr MHz	Bw MHz	Pols	Time secs	Notes
03may07	327	1.	A	120	On sky.
04may07	310	.01	A,B	300	sky and load
05may07	312	.01	A,B	16	sky with 100 Hz offset tone.

Processing the data:

The data processing steps were:

Compute the dc offset using a few million samples
Grab 16 seconds of data at a time, remove DC, and compute the spectrum. Decimate down to a few Khz.
Average these spectra till the end of the data set.
Normalize the spectrum to the total power integrated over the entire spectrum

Plotting the data:

03may07 data:
The first plot shows 60 Hz in the 03may07 baseband sampled data (.ps) (.pdf): This was 1 MHz baseband data centered at an rf frequency of 327 MHz. Only polA was sampled.

Top: +/- 300 hz about the center. 60 Hz is about 5% of the total system power.
Center: Blowup around 60 Hz. The 60 hz component is at close to 63 Hz. This was not seen in the wapp data. I'm not sure where this offset is coming from. It is also moving about a fair bit over the 300 seconds of data.
Bottom: The 3 harmonic of 60 hz. The vertical scale is about 1/10 th of the middle plot.

A dynamic spectra with .5 Hz resolution was made from the same data set.

There were about 150 2 second spectra in the 300 seconds of data.
+/- 200 hz are displayed.
The image has been scaled so that full range in the image is 6*sigma of the noise.
At 10 seconds and 110 seconds the 60 Hz narrows for a few seconds.

04may07 data
The 2nd plot shows 60 Hz in the 04may07 baseband sampled data (.ps) (.pdf): The data was 10 Khz of baseband data centered at an rf frequency of 310 MHz. Both polA and polb were sampled.

Top: PolA +/- 300 Hz about the center. 60 Hz is .01% of the system total power. This is a factor of 500 less than the data sampled on 03may07.
Middle: PolB +/- 300 Hz about the center. 60 Hz is .02% of the system total power. -60 Hz is also visible. This mixer may not have had it's i/q balanced perfectly.
Bottom: Blowup around 60Hz. It is offset from 60Hz by about 2 Hz.

05may07
The 2rd plot shows 60 Hz in the 05may07 baseband sampled data (.ps) (.pdf): The data was 10 Khz of baseband data centered at an rf frequency of 312 MHz. Both polA and polb were sampled. A tone at 312MHz + 100 Hz was added for a frequency reference.

Top: PolA +/- 300 Hz about the center. 60 Hz is .1% of the system total power. This is similar to the wapp data.
2nd: PolB +/- 300 Hz about the center. 60 Hz is .3% of the system total power. This matches the wapp values (the wapp data adds polA and polB).
3rd: Blowup around 60Hz. It is centered at 60 Hz unlike the previous 2 days.
Bottom: The +100 hz offset tone shows up at -100 Hz. The spectrum is flipped because of the 3 high side mixes and i have corrected for it.

The image shows they dynamic

Conclusions: (top)

The 327 receiver typically has a 60 hz component of about .3% of the integrated total power. Around 15apr07 this level jumped up to about 5% (2.5% in a 1/16hz channel times two channels). On 03apr07 somtime in the evening it went back to the .3% value.
When looking at dynamic spectra of 50MHz bw by time, the 60 Hz was modulating a large fraction of the and pass. It was strongest in the lower half of the band (centered at 327 MHz).
The large 60 Hz was in seen in wapp 2, wapp 4, the oscilloscope in the control room, and the ri sampled data so it is probably not tied to a particular downstairs piece of equipment.
Harmonics were seem up through 1900 Hz.
The amplitude of the 60 Hz was:

	Strength [total pwr]	Notes
p1693	2.5%High .3% Low	15apr07 to 03may07 After 03may07, before 15apr07
03mayRi	4.5%	62Hz
04mayRi	.03%	62Hz
05mayRi	.3%	60Hz

The 60 Hz was resolved by the 1/16th hz channels. The total contribution of the 60 hz was probably twice the value in the table (since it covered about 2 channels).

The ri data gave different results on 03may07 and 04may07. On 05may07 the values matched that of the wapp data. There may have been a configuration error on these two days causing the samplers to run at a different rate??.
This experiment used the wide band 327 filter.
On 3may07 in the morning, ganesh and dana went up and looked at the receiver in the dome. The 03may07 ri data (where the 60Hz was still strong) was taken after this.

processing: x101/070503/wappcmptp.pro, wappproctp.pro,327ri.pro, 070504/327ri.pro

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