[evlatests] antenna 14

[Mike Revnell]

It may be necessary to tweak the attenuation at the T4 inputs?


Mike Revnell
National Radio Astronomy Observatory
Socorro, New Mexico
mrevnell at nrao.edu
revnell at ieee.org

On Wed, 2 Nov 2005, Ken Sowinski wrote:

>
> Antenna 14 sort of works now.
>
> 14C is dead.  It wants about 40 dB of attenuation to
> get the sampler RMS down to where we want it and that
> seems like about 20 dB too much.  No correlated signal
> at all, but the SD voltage seems normal.  I guess, but
> have little evidence, that somethins is wrong in the
> downconverter.
>
> In general the antenna performance seems somewhat worse
> at the smapler input levels that Mike prefers.  A more
> careful check will be made later.
>
> It appears that with one gain parameter we can take our
> choice of underdriving the T4 or overdriving the requantizer
> in the transition module.  Three of the three working IFs
> have the ALC pegged, or close to pegged, when the sampler RMS
> is ~2.25.  Providing more drive to the sampler input helps,
> but requantizer overflows are reported.  This too will have to
> be looked at more carefully and checked with antenna 16.
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