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40m Log |
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Wed Jan 25 15:41:29 2017, Lydia, Update, IMC, 29.5 MHz modulation depth measurement plan
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Wed Jan 25 17:30:03 2017, Koji, Update, IMC, 29.5 MHz modulation depth measurement plan
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Wed Jan 25 19:39:07 2017, gautam , Update, IMC, 29.5 MHz modulation depth measurement plan
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Fri Jan 27 21:25:11 2017, Lydia, Update, IMC, 29.5 MHz modulation depth
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Sat Jan 28 01:25:51 2017, gautam, Update, IMC, 29.5 MHz modulation depth 
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Mon Jan 30 19:07:48 2017, gautam, Update, IMC, RF AM stabilization box pulled out
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Tue Jan 31 01:07:20 2017, Lydia, Update, IMC, RF AM stabilization box pulled out
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Tue Jan 31 13:46:34 2017, rana, Update, IMC, RF AM stabilization box pulled out
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Tue Jan 31 14:17:48 2017, gautam, Update, IMC, RF AM stabilization box pulled out
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Tue Jan 31 22:07:13 2017, gautam, Update, IMC, RF AM stabilization box revamp
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Tue Jan 31 22:28:39 2017, Lydia, Update, IMC, RF AM stabilization box pulled out
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Wed Feb 1 11:51:19 2017, Koji, Update, IMC, RF AM stabilization box pulled out
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Wed Feb 1 16:45:56 2017, Lydia, Update, IMC, RF AM stabilizer box Modification Plan
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Wed Feb 1 20:49:34 2017, rana, Update, IMC, RF AM stabilizer box Modification Plan
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Wed Feb 1 23:13:30 2017, Lydia, Update, IMC, RF AM stabilizer box Modification Plan
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Sun Feb 5 21:56:50 2017, Lydia, Update, IMC, 29.5 MHz stabilizer box replacement
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Tue Feb 7 12:01:10 2017, Lydia, Update, IMC, 29.5 MHz stabilizer box replacement
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Tue Feb 7 17:00:55 2017, Lydia, Update, IMC, 29.5 MHz stabilizer box replacement
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Fri Feb 10 02:14:10 2017, gautam, Update, IMC, 29.5 MHz stabilizer box replacement
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Fri Feb 10 11:41:43 2017, Lydia, Update, IMC, 29.5 MHz stabilizer box replacement
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Fri Feb 10 13:24:28 2017, rana, Update, IMC, 29.5 MHz stabilizer box replacement
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Fri Feb 10 18:21:21 2017, gautam, Update, IMC, IMC Demod board
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Fri Feb 10 19:32:15 2017, Koji, Update, IMC, IMC Demod board
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Sun Feb 12 01:16:57 2017, gautam, Update, IMC, IMC length loop - summary of changes    
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Mon Feb 13 11:55:14 2017, rana, Update, IMC, IMC length loop - summary of changes
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Mon Feb 13 13:34:44 2017, gautam, Update, IMC, IMC length loop - bad SMA cable replaced
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Mon Feb 13 19:44:55 2017, Lydia, Update, IMC, Front panel for 29.5 MHz amplifier box
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Wed Mar 1 21:15:40 2017, Lydia, Update, IMC, Front panel for 29.5 MHz amplifier box
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Wed Mar 1 23:56:09 2017, gautam, Update, IMC, Front panel for 29.5 MHz amplifier box
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Thu Mar 2 20:32:18 2017, Lydia, Update, IMC, Front panel for 29.5 MHz amplifier box
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Wed Feb 15 23:54:13 2017, gautam, Update, IMC, IMC saga continues... 
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Fri Feb 17 20:10:18 2017, gautam, Update, IMC, WFS servos turned back on
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Sat Feb 18 14:09:06 2017, rana, Update, IMC, WFS servos turned back on
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Sat Feb 18 21:50:48 2017, gautam, Update, IMC, WFS servos turned back on
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Sun Mar 5 12:41:23 2017, gautam, Update, IMC, WFS servo-steppin  
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Message ID: 12821
Entry time: Fri Feb 10 19:32:15 2017
In reply to: 12820
Reply to this: 12822
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Author: |
Koji |
Type: |
Update |
Category: |
IMC |
Subject: |
IMC Demod board |
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The input impedance of the mixer is not constant. As the diode switches, it changes dynamically. Because of this, the waveform of the LO at the mixer input (i.e. the amplifier output) is not sinusoidal. Some of the power goes away to harmonic frequencies. Also, your active probe is calibrated to measure the power across the exact 50Ohm load, which is not in this case. The real confirmation can be done by swapping the mixer with a 50Ohm resistor. But it is too much. Just confirm the power BEFORE the amp is fine. +/-1dB does not change the mixer function much.
Instead, we should measure
- Orthogonality
- Gain imbalance
of the I/Q output. This can be checked by supplying an RF signal that is 100~1kHz away from the LO frequency and observe I&Q outputs. |