[evlatests] [evla-sw-discuss] parameter simplification for the VHF receivers

[Ravi Subrahmanyan]

At add some more info that may be relevant:
The 55-85 MHz data and 270-470 MHz data come from different feeds on
the antenna, and will appear in the data in different
subbands/spectral windows.......Ravi

On Thu, Jun 28, 2012 at 11:56 AM, Dan Mertely <dmertely at nrao.edu> wrote:
> The 55-85 MHz VHF low-band and the 270-470 MHz UHF
> high-band passbands get combined internally in the
> front end and get passed to the T301 up-converter
> module as a single passband (with 2 "humps").  The
> T301 uses a 1024 MHz LO to mirror-flip the spectrum
> up into L-band, where it is treated as if it were L-
> band by the rest of the antenna electronics.  (Paul,
> Chuck, is that a reasonable summary?)  -Mert
>
>
> Bryan Butler wrote:
>> do they come through different receivers within the box?
>>
>> i'm concerned about being able to distinguish between them in the SDM.
>>
>>       -bryan
>>
>>
>> Ken Sowinski wrote, On 6/27/12 9:30 AM:
>>> Currently parmainator distinguishes between 75 MHz and 300 MHz for
>>> band related paramters.  The parameters of interest are subreflector
>>> rotation and focus and band-dependent delays.  Also there are T_cals,
>>> which are now obsolete in the paramters DB, and tables of attenuator
>>> settings, also obsolete.
>>>
>>> I suggest that we have only one band code "VHF" to select the low
>>> frequency receivers.  Receiver.java will transform any reference
>>> to "75MHz" or "300MHz" to "VHF".  This allows us to keep only
>>> one set of parameters in the DB, rather than two identical sets;
>>> prevents possible mistakes when two sets are maintains; more
>>> accurately reflects the current hardware; and, eliminates the confusing
>>> necessity of having to know whether the script selected "75MHz" or
>>> "300MHz".
>>>
>>> The rational is that there is one receiver box containing all
>>> receivers.  Its single output (dual polarization) is conneted
>>> to one T301 input.  Regardless of which band is selected, the
>>> hardware configuration is the same and the same wideband signal
>>> is presented to the T304.
>>>
>>> Would doing this prevent anything that would be practical and useful
>>> with the current scheme?
>>> _______________________________________________
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>>> http://listmgr.cv.nrao.edu/mailman/listinfo/evla-sw-discuss
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