[evlatests] Ka band power level pulsing (fwd)

[Jim Jackson]

I take it this means we are switching one or more of the mechanical 
switches in the UX converter (probably twice) every 10 seconds. If 
so, a fix needs to be found for this before we start using the 
converted path regularly.  This is really not good for the long term 
reliability and performance of these expensive switches.

Jim



At 09:24 AM 6/12/2008, Ken Sowinski wrote:
>I thought the following message deserves a wider audience.
>The context is that Rick and Bob found a ten second glitch
>in TP of IF B while using the conversion path of the T303
>and doing tipping scans.  The origin turns out to be in how
>the M301 is commanded when the conversion path is requested;
>a solution is proposed.
>
>
>---------- Forwarded message ----------
>Date: Tue, 10 Jun 2008 14:29:55 -0600 (MDT)
>From: Ken Sowinski <ksowinsk at aoc.nrao.edu>
>To: Ken Sowinski <ksowinsk at aoc.nrao.edu>
>Cc: Barry Clark <bclark at aoc.nrao.edu>, Robert Long <rlong at aoc.nrao.edu>,
>      Robert Hayward <rhayward at aoc.nrao.edu>, Rick Perley 
> <rperley at aoc.nrao.edu>
>Subject: Re: Ka band power level pulsing
>
>Staring at the block diagram and a moment of thought explained
>what is happening.
>
>When selecting K, Ka or Q band the M301 sets the T303 output
>switches to replicate the direct connection into both outputs,
>so that A is copied into B and C into D.  When the conversion
>path is to be used one of the switches must be reset to route
>the mixer output to IF B and D and this is done with a separate
>command to the M301 after the band select command.  It is this
>sequence of commands which causes a glitch in TP at every scan
>initiation.  In pointing or tipping scans, as currently implemented,
>this is every ten seconds.
>
>If the signal interruption is deemed a problem we can make it
>go away by inventing three more band codes for the M301 to
>represent K, Ka and Q band using the T303 conversion path.
>U band is not at issue because the M301 already sets the switches
>correctly in that case.
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