[evlatests] antenna 24 AC - update

[Jim Jackson]

Actually, Rob replaced that L302 synthesizer first thing this morning - 
Sorry, I forgot to send out the message that he did it.  This L302 has the 
new non-AGC firmware in it.  If it's still doing the exact same thing, then 
something else must be wrong.  If it's happening on X-band, then the only 
other thing I can see they have in common is that A and C use the auto 
level setting in the T304.  Does everything seem OK with that?  Can anyone 
think of a way the auto level setting function misbehaving could cause this 
symptom?

The only other thing I can think of is the cable length to the L302 
reference inputs though I thought that problem displayed different symptoms.

Jim

At 04:22 PM 1/16/2007, Ken Sowinski wrote:
>On Wed, 10 Jan 2007, Jim Jackson wrote:
>
>>Sorry, I lied - we  don't have the spare L302 rev C needed to do this right
>>now. We need to get one ready and will make the change when we can.  We
>>could break antenna 17 to fix it but since that antenna is ready for first
>>fringes as of today and 24 is still useable the way it is, Rob and I both
>>decided we would rather not do that.
>>
>>After checking the L302-1 in 24 and thinking about this a little, I think
>>this could be a symptom of the AGC instability we have seen in some L302's
>>- this particular module is still operating using the AGC based firmware
>>(rev 0.201). The latest firmware (rev 0.21 and up)  eliminates the AGC and
>>sets output level using a lookup table. The synthesizers we have done that
>>to seem considerably more stable in output level stability  and lock
>>reliability.  Unfortunately we can't just upload the MIB new firmware to
>>the module - it has to come to the lab and be run through a calibration
>>procedure to generate the lookup table.
>>
>>We will advise when we make the change
>
>Today it looks like 24AC is still doing this so I guess
>nothing has been done yet.  If it looks like it will be
>a while before the lab calibration can take place I vote
>for cannibalizing antenna 17 now that we have seen first
>fringes.
>
>The issue we have with antenna 17 is apparant poor sensitivity
>and one IF pair is sufficient to chase that.
>
>Ken