[evlatests] Ant. 13, IFs BD: ~60d phase jumps every 20 seconds at C, X, L bands

[Bryan Butler]

given this problem with cable length changes, is it time to start investigating 
the ALMA solution to this problem?

	-bryan


On 7/19/06 17:36, Jim Jackson wrote:
> This is curious. We noticed earlier this afternoon that the two L302's in 
> Antenna 13 seem to have different firmware (or something else) in the 
> MIB.  Even though both claim to be MIBVERSION 0.99 and MODULEVERSION 0.20, 
> there are two missing monitor points on the L302-2 in antenna 13 and the 
> L302-1 in Antenna 24  The monitor points are  M_LOCKH and C_LOCKH.
> 
> Pete and Matt - Are we sure these modules all have the same MIB and FPGA 
> firmware?
> 
> Adding length to the LVDS heartbeat cable to these modules is a 
> problem.  The project's worth of twinax cables were purchased from 
> Tensolite as an expensive special order with custom connectors.  They are 
> all the same length.  We could vary the length of the 128MHz coax cable 
> feeding the clock to the FPGA.
> 
> Jim
> 
> 
> 
> At 09:54 AM 7/19/2006, Rick Perley wrote:
>>     But why would this non-subtle behavior be absent before July 7th?
>>And why only
>>with antenna 13, IFs B and D?
>>
>>Barry Clark wrote:
>>
>> >This is almost certainly the heartbeat capture uncertaintly glitch we
>> >saw in the lab.  I am happy that things are now working well enough in
>> >the field that we notice it.  It could probably be cured by adding a foot
>> >of cable to the LVDS heartbeat cable.  Only worth doing if this L302 is
>> >in final form.
>> >
>> >I've lost track of what the revision state of this L302 is.  The vaunted
>> >spreadsheets in techdocs contain no useful information for L302s.
>> >
>> >
>> >
>> >
>> >>AR603 data taken between July 12th and July 15th show an odd behavior
>> >>for ant. 13, IFs BD (AIPS IF 2 RR & LL): frequent ~60 degree phase jumps
>> >>within a scan.
>> >>
>> >>
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> 
> 
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