Responsible: Effland

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RID 1712

Doc. Title
Specification, Section 5.7.1 Originator: James Lamb Date: 2007-09-09

Description:
This specification is a bit vague in what its intent is. Since the design has presumably be

verified with reference to the overall ALMA aperture efficiency and spillover specifications,

the goal should be to check that there are no manufacturing or assembly errors. Is the 90

% efficiency from a theoretical calculation or prototype measurements and how much lower

than the the optimum is it. (I'd think that the theoretical value was closer to 95 %, so this

is a big difference).



The edge taper is specified without any limits or frequency. The value could vary by 0.5 dB

over the band. Since a beam pattern measurement is presumably made to determine this,

why not provide provide a pattern Pass/Fail template?
Suggested Solution:

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RID 1713

Doc. Title
Band 6 Cartridge Test Procedure: IF Originator: James Lamb Date: 2007-09-09

Output Power

Description:
Sec 2

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This section is inconsistent with the specifications (Sec. 5.3.2 IF power

variations) which specify the power variation, not the gain variation. In the

specifications it is not clear what the cartridge input should be for the

specified limits on power variation.



Discrepancy needs to be resolved.
Suggested Solution:

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RID 1714

Doc. Title
Band 6 Test Procedure: RF Beam Originator: James Lamb Date: 2007-09-09

Efficiency

Description:
The efficiency is specified at the secondary mirror, but the measurement is made in the

near-field. Meeting the specification in the near-field does not guarantee that it is met at

the secondary. Equality of the two is only assured if the beam behaves according to the

calculation, but errors in the beam can result in the specification being met in the near

field, but not in the far field (and this is not just theoretical, I have seen this

experimentally).



Consider an alternative. E.g., integrate the beam pattern measurement
Suggested Solution:
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Printed 2007-09-18 16:52:38 Page 4 of 8
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