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%META:TOPICINFO{author="CarlBignell" date="1166204280" format="1.0" version="1.1"}%
%META:TOPICPARENT{name="WebHome"}%
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For any observer who is currently uses the spectrometer for spectral line work a potential problem may be encountyered when trying to balance the system. This problem is a result of some hardware improvements for improving the balancing process in general but at the same time some dependencies arose which are not covered automatically by the software in configuring the system. To our knowledge this problem does not exist for the spectral processor.
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After balancing the system when configuring the spectrometer a message indicating that the spectrometer is out of balance and the amount is more than ~ 2.5 db (for on-offs this would apply to either the on or off).
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The table at the end of this message summarizes the IF level requirements in making sure the system is balanced. This will depend on receiver, IF bandwith, spectrometer bandwidth and spectrometer levels (3 or 9). The system automatically tries to balance with an IF level of 1.0 volt. If your configuration paramters fit into the table below and the IF level for balancing is not 1.0 Volt then the instructions below indicate how to set the balance to the propoer voltage in your configuration instructions.
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Receiver group definitions:
A == L-band, C-band, X-band, Ku-band
B == S-band, K-band, Ka-band, Q-band
C == PF1-340, PF1-450, PF1-600, PF1-800, PF2
Rcvr IF BW Spect. 12.5 or Spect. 12.5 or Spect. 200 or DCR
Group GHz 50 MHz BW, 9 level 50 MHz BW, 3 level 800 MHz BW
----- ----- ------------------ ------------------ ------------- -----
A 0.02 0.1 V 0.5 V 1.0 V 1.0 V
A 0.08 0.1 V 0.5 V 1.0 V 1.0 V
A 0.320 1.0 V 1.0 V 1.0 V 1.0 V
A 1.280 1.0 V 1.0 V 1.0 V 1.0 V
B 0.08 1.0 V 1.0 V 1.0 V 1.0 V
B 0.320 1.0 V 1.0 V 1.0 V 1.0 V
B 1.280 1.0 V 1.0 V 1.0 V 1.0 V
A,B AllPass 3.0 V 5.0 V 1.0 V 1.0 V
C AllPass 1.0 V 1.0 V 1.0 V 1.0 V
The AllPass mode in the IF Rack is automatically selected for the prime focus
receivers. The balance voltage in the PF receiver manager should be 1.0 V
(default behavior).
To determine the IF BW that you will be using take the largest separation
of frequencies in your configuration and then choose the next largest filter.
Note that if your frequencies are separated by more than 1.28 GHz you will
use the AllPass filter.
To set the recommended balance voltages add one of the following lines
(whichever is appropriate) to your configuration:
iftarget = 0.1
iftarget = 0.5
iftarget = 1.0
iftarget = 3.0
iftarget = 5.0
Contributers: S. White, R. Maddalena, T. Minter
-- CarlBignell - 15 Dec 2006 |