[evlatests] S band fringes

[Rick Perley]

    ... as there remains doubt about which antenna is correctly 
polarized, I think the best course of action is to have Ken trick the 
system into thinking it's C-band, and X-correlate the two antennas 
against the C-band system (where we think we've got it right).  He says 
he can do this next week...

   

Charles Kutz wrote:
> Yesterday, 
>
> I took a look at the two receivers and turned off their biases to the 
> RCP channel. On antenna 9 the RCP went dead as viewed at the output of 
> the T5. Turning off the RCP bias in antenna 28 resulted in the LCP going 
> dead as viewed at the the T5. I had John go out and swap the heliax at 
> the receiver output and hang a tag on the receiver so we know what happened.
>
> I think that this points to either crossed output coaxes inside the 
> receiver or crossed heliax at the output of the receiver. Haven't yet 
> had a chance to talk to John about what he actually was able to 
> ascertain in antenna 28.
>
> For now...
>
>
> Chuck
>
>
> Bob Hayward wrote:
>   
>> We should first establish whether there is a mix up in the heliax cables 
>> between the receiver and the LO/IF Rack. If not, then the problem may be 
>> in the connections to the hybrid coupler inside the receiver.
>>
>> There is a simple test we can do in the lab to confirm whether future 
>> S-Band receivers are polarized correctly. Someone on the S-Band 
>> technical team should come and talk to me if they are unaware of it. 
>> This step may have been missed on one (or both) of the 1st two receivers 
>> sent into the field.
>>
>> Just a reminder that merely swapping the output cables at the receiver 
>> on the antenna is not a perfect fix. The Tcal values given to Ops will 
>> be imposed on the wrong polarization unless they are swapped in the 
>> database as well. Also, there will likely be an opportunity for 
>> confusion in the future. For example, if there is a maintenance write-up 
>> for a dead LCP amp we could easily open up the receiver and waste time 
>> working on the wrong channel as it will actually be the LNA in the 
>> physical "RCP" location within the Dewar that is buggered.
>>
>> -Bob
>>
>>
>> Ken Sowinski wrote:
>>   
>>     
>>> Antennas ea09 and ea28 now have S band receivers installed.
>>> Fringes were obtained but the two systems have opposite
>>> polarization sense.  I will leave it to others to decide
>>> which one to swap.
>>>
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>
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