[evlatests] [Vlite-external] EA14 polarization and VLITE

[Rick Perley]

     ... in case this is not yet sufficiently confusing, remember that 
the new MJP design dipoles are rotated 45 degrees w.r.t. the antenna's 
principle axes.  So 'H' and 'V' will have no physical meaning any more 
...  (fortunately, P-band remains o.k.)
     We'll need an easy-to-remember way of identifying which pair of MJP 
feeds correspond to which IF channel ...


On 06/26/2014 05:53 PM, Paul Harden wrote:
> We swapped the polarization Thursday on VLITE antenna 14 and should now
> be correct.
>
> Here's the problem.  Nomenclature for the low band linear polarization
> has been standardized such that:
> Horizontal antenna = RCP
> Vertical antenna = LCP
>
> The input connectors on the VLITE module are labled "Ch. 1" and "Ch. 2."
>    There is no indication what polarization is assigned to what channel.
>    The 50/50 choice used was obviously wrong.
>
> What polarization is assigned to Ch.1 and Ch.2?
>
> When installed, RCP was connected to Ch. 1 and LCP to Ch. 2, which
> caused the reported swapped polarization.
>
> LCP now goes to Ch. 1
> RCP now goes to Ch. 2
>
> This channel assignment needs to be standardized, and perhaps some "LCP"
> and "RCP" labels made to eliminate the channel references.
>
> Also, there are two 30dB coaxial amplifiers on the Ch.1 and Ch.2 inputs
> on the VLITE module, amplifying the low band receiver output by 30dB.
> Typical LBR receiver output is about -75 dBm/MHz on the cold sky,
> meaning about -45 dBm/MHz input to VLITE.  I don't know how much
> internal amplification there, the ADC range, or the compression points,
> but seems this much amplification would seriously limit the dynamic
> range and gain headroom of the VLITE module.
>
> Paul
> _______________________________________________
> Vlite-external mailing list
> Vlite-external at listmgr.cv.nrao.edu
> http://listmgr.cv.nrao.edu/mailman/listinfo/vlite-external