[GMVAtech 8] Re: Autocorrelation test using ALMA mode at Yebes

[Pablo de Vicente]

Hello Uwe,

   Yes, we have used the same setting.

  Best regars

Pablo.


El 13/02/17 a las 09:59, Uwe Bach escribió:
> 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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>
>
>
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