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 Fri Apr 10 19:09:48 2009, Jenne, Update, PSL, PMC LO Calibration 
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 Sat Apr 11 00:45:41 2009, Yoichi, Update, PSL, PMC LO Calibration
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Sun Apr 12 19:27:20 2009, rana, Update, PSL, PMC LO Calibration
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Mon Apr 13 08:59:57 2009, steve, Update, PSL, mixers on order
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Message ID: 1471
Entry time: Fri Apr 10 19:09:48 2009
Reply to this: 1473
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| Author: |
Jenne |
| Type: |
Update |
| Category: |
PSL |
| Subject: |
PMC LO Calibration |
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I measured the RF LO output level from the PMC's LO board which goes directly into the LO input on the PMC Servo board. This goes hand-in-hand with Rana's thoughts
that we might be giving the PMC mixer a too-low LO value, and we might need to switch out the mixer. Steve ordered some new mixers today to try out.
The RF Output Adjust slider (on the C1:PSL_PMC_PS screen) goes from 0-10V; The nominal value (or at least the value I found it at today) is 2.014V.
To measure the RF level: I unlocked the Mode Cleaner and turned off the ISS servo per Yoichi's suggestion. I then unplugged the input to the PMC servo board's LO input,
and put that cable into a 300MHz 'scope, with 12dB attenuation. The 'scope was AC coupled, with the input set to 50Ohms.
I then changed the RF Output Adjust slider in increments of 0.5, and measured the peak-to-peak values on the scope. In the table and on the plots, I've taken into account
the 12dB attenuation. i.e I actually measured 964mV, so 964mV*10^.6 = 3838mV.
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RF Output Adjust | Output measured on scope | Oscillator Output Monitor
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[V] | [Vpp] | [no units given on MEDM screen]
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| All \pm 0.0159 | all of this column is NEGATIVE
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0.0000 | 3.838 | 0.007
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0.5000 | 3.854 | 0.007
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1.0000 | 3.838 | 0.006
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1.5000 | 3.838 | 0.007
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2.0000 | 3.838 | 0.006
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2.5000 | 3.838 | 0.007
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3.0000 | 3.838 | 0.007
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3.5000 | 3.838 | 0.007
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4.0000 | 3.838 | 0.007
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4.5000 | 3.822 | 0.007
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5.0000 | 3.822 | 0.012
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5.5000 | 3.790 | 0.076
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6.0000 | 3.758 | 0.257
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6.5000 | 3.694 | 0.555
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7.0000 | 3.615 | 0.931
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7.5000 | 3.535 | 1.277
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8.0000 | 3.456 | 1.532
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8.5000 | 3.392 | 1.709
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9.0000 | 3.344 | 1.829
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9.5000 | 3.312 | 1.908
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10.0000 | 3.296 | 1.966
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I think it's kind of funky that it's so flat for ~half the slider. Also, the third column includes the Oscillator Output Monitor value from the MEDM screen at various RF Adjust slider values. All of these should be negative (i.e. -0.007), but the TABLE function doesn't like "-" signs. I don't know if this information is degenerate with the 'scope measurements, or if it's an indicator of what (might be) wrong.
After finishing, I plugged the cable back into the PMC servo board as it was, turned back on the ISS and relocked the PMC and the MC. |
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