[GMVAtech 7] Re: Autocorrelation test using ALMA mode at Yebes

[Uwe Bach]

Thanks Pablo, a very useful test and very nice results!

Just to be sure that we did the correct settings in the past: Did you 
use the same settings for the Fila10G and DBBC as for the previous full 
band test at 86 GHz?

Best wishes
Uwe


On 02/13/2017 09:46 AM, Pablo de Vicente wrote:
> Hello
>
>   Javier and me have been doing some tests to check if the ALMA mode was
> working properly at Yebes. Last Friday we tracked W3OH and recorded two
> scans with different LO setups to get an autocorrelation spectra of the
> 22 GHz maser. See the first attachment.
>
>   We were using the ALMA mode with the 22 GHz receiver because the H2O
> maser is quite bright. Our first setup was setting the LO frequency to
> get the line close to 250 MHz in the base band. The result of this setup
> is in the second attachment. In order to check if the line that we
> detect was the real maser we moved the LO 100 MHz up and got the third
> figure that I attach. We expected the line to come up close to 150 MHz
> in the baseband.
>
>   In order to have a good snapshot of the line profile from "m5spec" we
> increased the number of spectral points to 32000. The line profile is
> very similar to what we get from our FFTS except that the line is
> reversed, which is something that we expect since the signal is coming
> in the second Nyquist zone when entering the DBBC2 and the whole band is
> reversed. Therefore when increasing 100 MHz the LO, the line is shifted
> towards upper channels (~ 350 MHz) in the DBBC2 autocoreelation
> frequency base band whereas using the FFTS, our single dish spectral
> backend, the line is shifted to lower channels (~ 150 MHz) in the
> frequency base band. I hope I have not confused you with my text.
>
> Commands used:
>
> Immediately after recording two of these with a different LO setup:
>
>   mk5=scan_set=::+20000000
>   mk5=disk2file=/home/oper/data/systest.vdif:::w
>
> At the Flexbuff:
>
>   cp systest.vdif alma_h2o_centered.vdif
>   m5spec systest_alma_h2o_centered.vdif VDIF_8000-4096-2-2 32000 4096
> spec_alma_h2o_centered.out
>
>   cp systest.vdif systest_alma_h2o_shifted.vdif
>   m5spec systest_alma_h2o_shifted.vdif VDIF_8000-4096-2-2 32000 4096
> spec_alma_h2o_shifted.out
>
>  Cheers
>
>  Pablo.
>
>
>
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>

-- 
_________________________________________
Uwe Bach
Max-Planck-Institut fuer Radioastronomie
Radioobservatorium Effelsberg
Max-Planck-Str. 28
53902 Bad Münstereifel-Effelsberg
http://www.mpifr.de/staff/ubach
phone: +49 (0)2257 301 168
fax: +49 (0)2257 301 105

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