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

[Dan Mertely]

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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