[evlatests] EVLA Antenna work today

[Jim Jackson]

The cable on the Antenna 13 L-Band receiver was simply not installed 
correctly, probably after someone ran some test or another.  This is a 
procedural issue - people are supposed to be tightening SMA connectors to a 
specified torque using wrenches that we have on hand.  Additionally, Heliax 
cables are somewhat prone to self loosening due to the stiffness of the 
cables and movement of the antennas - though not to the extent that this 
one was loose.  This type of cable has been used in systems around here for 
years due to its very high performance and people are relatively used to 
dealing with it.

The first couple sets of cables from the correlator room to the D-racks 
have been problematic. They were fairly esoteric Foam Flex and LMR-600 
cables which are stiff, expensive and difficult to terminate. We are now 
using a different cable - basic RG-214 1/2" coax.  We are also now 
considering going to RG-223 cable due to cost issues - this cable was never 
budgeted in the project and will be discarded after the transistion..  We 
will be testing the RG-223 shortly - it would save about $30-35K.over the 
RG-214.

Jim

Jim

At 08:31 PM 2/28/2006, Walter Brisken wrote:

>>Antenna 13 L-Band RCP - The heliax cable on the output of the receiver 
>>was loose to the point where we were amazed it had been working at all. 
>>It has been tightened.
>>
>>Antenna 14 IF B Intermittent loss of power - The cable from the 
>>correlator room wall bulkhead panel to the D-Rack is broken. Lee is 
>>making a replacement as I write this and it will be installed tomorrow.
>
>I'm kind of curious how cabling issues like the above happen and if there 
>is something, either procedural or technical, that can be done to improve 
>reliability of cabling.  Given the number of connectorized cablings that 
>the (E)VLA has (10^4 to 10^5 or so, perhaps), if every cable has on 
>average one failure in its lifetime of say 30 years, that would be 1 to 10 
>cable problems every day!
>
>-W
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