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In the 'setup' section of the v2d file you can set, e.g.<br>
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freqId=1,2 <br>
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to select just the second and third frequency setups in the input file. This can be a bit fragile in complex, changing setups, but should be straightforward in your case, assuming all jobs have both VLA and LWA participation.<br>
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Cheers,<br>
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Cormac<span id="ms-outlook-android-cursor"></span></div>
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<div id="divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" style="font-size:11pt" color="#000000"><b>From:</b> Jayce Dowell <jdowell@unm.edu><br>
<b>Sent:</b> Wednesday, March 24, 2021 9:32:54 AM<br>
<b>To:</b> Reynolds, Cormac (CASS, Kensington WA) <Cormac.Reynolds@csiro.au>; adeller@astro.swin.edu.au <adeller@astro.swin.edu.au><br>
<b>Cc:</b> difx-users@listmgr.nrao.edu <difx-users@listmgr.nrao.edu><br>
<b>Subject:</b> Re: [Difx-users] complex support</font>
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<div class="PlainText">Hi Cormac,<br>
<br>
I am not sure which probably means no. How/where would I do that?<br>
<br>
Jayce<br>
--<br>
On 3/23/21 7:27 PM, Reynolds, Cormac (CASS, Kensington WA) wrote:<br>
> [EXTERNAL]<br>
> <br>
> hi Jayce,<br>
> <br>
> have you taken steps (e.g. by freqId selection) to make sure you are<br>
> not getting correlations between the parent bands - e.g. from VLA-VLA<br>
> or from LWA-LWA stations? By default DiFX will correlate anything it<br>
> can find that seems to match.<br>
> <br>
> cheers,<br>
> Cormac<br>
> <br>
> On Tue, 2021-03-23 at 19:10 -0600, Jayce Dowell via Difx-users wrote:<br>
>> Hi Adam & Chris,<br>
>><br>
>> I've moved on to the VLA+LWA data and am running into a new<br>
>> problem. I<br>
>> have my frequency setups as:<br>
>><br>
>> # FREQ TABLE #######!<br>
>> FREQ ENTRIES: 2<br>
>> FREQ (MHZ) 0: 71.09999999441<br>
>> BW (MHZ) 0: 9.80000000000<br>
>> SIDEBAND 0: U<br>
>> NUM CHANNELS 0: 392<br>
>> CHANS TO AVG 0: 1<br>
>> OVERSAMPLE FAC. 0: 1<br>
>> DECIMATION FAC. 0: 1<br>
>> PHASE CALS 0 OUT: 0<br>
>> FREQ (MHZ) 1: 71.99999999441<br>
>> BW (MHZ) 1: 8.00000000000<br>
>> SIDEBAND 1: U<br>
>> NUM CHANNELS 1: 320<br>
>> CHANS TO AVG 1: 1<br>
>> OVERSAMPLE FAC. 1: 1<br>
>> DECIMATION FAC. 1: 1<br>
>> PHASE CALS 1 OUT: 0<br>
>><br>
>> In my data streams table I have the LWA stations recording complex<br>
>> double sideband with frequency setup 0 and one zoom band of setup 1.<br>
>> The VLA antennas are set real upper sideband with frequency setup 1<br>
>> and<br>
>> no zoom band. I think this is what I want and mpifxcorr doesn't<br>
>> complain when I run it. However, difx2fits immediately segfaults<br>
>> when I<br>
>> try to build a FITS-IDI file. Any suggestions?<br>
>><br>
>> Jayce<br>
>> --<br>
>> On 3/10/21 4:19 PM, Adam Deller wrote:<br>
>>> * [EXTERNAL]*<br>
>>><br>
>>> **<br>
>>> Glad to hear it!<br>
>>><br>
>>> On Thu, 11 Mar 2021 at 09:58, Jayce Dowell <jdowell@unm.edu<br>
>>> <<a href="mailto:jdowell@unm.edu">mailto:jdowell@unm.edu</a>>> wrote:<br>
>>><br>
>>> Hi Chris,<br>
>>><br>
>>> After some digging I was able to get to the bottom of this and<br>
>>> I am now<br>
>>> getting results that I am happy with. It was a combination of<br>
>>> switching<br>
>>> over to trunk and fixing a bad assumption in my VDIF conversion<br>
>>> that<br>
>>> everyone represents four-bit complex integers in the same way.<br>
>>><br>
>>> Jayce<br>
>>> --<br>
>>> On 2/4/21 3:08 PM, Phillips, Chris (CASS, Marsfield) wrote:<br>
>>> > [EXTERNAL]<br>
>>> ><br>
>>> > Hi Jayce<br>
>>> ><br>
>>> > I'm working the data from the Long Wavelength Array and I am<br>
>>> trying to see if we can move from our homegrown correlator to<br>
>>> DiFX.<br>
>>> The two modes I need to support are a LWA-only mode with<br>
>>> homogeneous<br>
>>> data and an "eLWA" mode with heterogeneous data that combines<br>
>>> the<br>
>>> LWA stations with the VLA 4-band system. For the LWA-only mode<br>
>>> I<br>
>>> have 4+4-bit complex voltage data from two 19.6 MHz wide<br>
>>> spectral<br>
>>> windows. I am currently converting these data from the LWA<br>
>>> format<br>
>>> into two VDIF files, one per window, for correlation with<br>
>>> DiFX. My<br>
>>> .input file describes the data as:<br>
>>> >><br>
>>> >> DATA FORMAT: INTERLACEDVDIF/0:1<br>
>>> >> QUANTISATION BITS: 4<br>
>>> >> DATA FRAME SIZE: 7872<br>
>>> >> DATA SAMPLING: COMPLEX_DSB<br>
>>> >> DATA SOURCE: FILE<br>
>>> >><br>
>>> ><br>
>>> > I have never personally tested complex_dsb data with<br>
>>> interlaced<br>
>>> vdif. I have no idea if there could be any “interaction” with<br>
>>> the<br>
>>> VDIF interleaving and the specific data type (I would have<br>
>>> thought<br>
>>> not, but you never know).<br>
>>> ><br>
>>> > The issue could also be with interpreting the interlaced<br>
>>> VDIF,<br>
>>> not the complex double sideband.<br>
>>> ><br>
>>> > Once you have tested using trunk, not the released version,<br>
>>> I<br>
>>> would try and use some of the vdifio utilities to try and<br>
>>> convert<br>
>>> the interlaced VDIF into plain VDIF - either extracting out one<br>
>>> thread, or merging into multichannel single thread VDIF. You<br>
>>> would<br>
>>> obviously need to update the DIFX .input (and or .v2d) file and<br>
>>> vexfile to match the new setup.<br>
>>> ><br>
>>> > I would also be using the m5access tools to do things like<br>
>>> make<br>
>>> the autocorrelation (both before and after fiddling with the<br>
>>> data<br>
>>> layout). Check DIFX gives the same auto shape as you get with<br>
>>> m5spec. If you use a modulated noise source, folding the data<br>
>>> (m5fold) on the period of the noise cal can be very informative<br>
>>> also. Also look at the headers and check that the # frames/sec<br>
>>> etc<br>
>>> are what you expect (before and after merging threads etc). If<br>
>>> you<br>
>>> decide it is the interlacing is the issue, I suspect you will<br>
>>> need<br>
>>> to discuss with Walter.<br>
>>> ><br>
>>> ><br>
>>> >> I am less sure about DiFX supporting our eLWA mode. For<br>
>>> this we<br>
>>> have the same 4+4-bit complex voltage data from the LWA<br>
>>> stations but<br>
>>> with a bandwidth of 9.8 MHz. We are combining this with 4-bit<br>
>>> real<br>
>>> voltages from the VLA with 8 MHz of bandwidth and a slightly<br>
>>> different frequency setup. We currently process these data by<br>
>>> shifting the center frequency of the LWA data to match that of<br>
>>> the<br>
>>> VLA, running two F-engines with different channelization to<br>
>>> arrive<br>
>>> at the same channel width for both data sources, and then cross<br>
>>> correlate what overlaps. Is this mode something that DiFX<br>
>>> supports?<br>
>>> >><br>
>>> ><br>
>>> > Can you represent this data as VDIF? If you you can probably<br>
>>> handle the different setup using zoom bands. However if this<br>
>>> can be<br>
>>> done will really depend on the EXACT setup. Basically you need<br>
>>> to be<br>
>>> able to channelise the two setups with the same final frequency<br>
>>> resolution (ie different FFT sizes will be needed, with the<br>
>>> ratio of<br>
>>> the FFT size matching the ratio of the bandwidth difference.<br>
>>> But the<br>
>>> sky frequency of the frequency points out of the FFT need to<br>
>>> match<br>
>>> exactly (ie even if you could achieve the same frequency<br>
>>> resolution,<br>
>>> if the fine channels are offset by 1/3 of a channel you will<br>
>>> have<br>
>>> problems (if that offset is a simple integer ratio, you can<br>
>>> just use<br>
>>> a higher frequency resolution)<br>
>>> ><br>
>>> > I hope this makes sense.<br>
>>> ><br>
>>> > Cheers<br>
>>> > Chris<br>
>>> ><br>
>>><br>
>>><br>
>>><br>
>>> --<br>
>>> !=============================================================!<br>
>>> A/Prof. Adam Deller<br>
>>> ARC Future Fellow<br>
>>> Centre for Astrophysics & Supercomputing<br>
>>> Swinburne University of Technology<br>
>>> John St, Hawthorn VIC 3122 Australia<br>
>>> phone: +61 3 9214 5307<br>
>>> fax: +61 3 9214 8797<br>
>>><br>
>>> office days (usually): Mon-Thu<br>
>>> !=============================================================!<br>
>><br>
>> _______________________________________________<br>
>> Difx-users mailing list<br>
>> Difx-users@listmgr.nrao.edu<br>
>> <a href="https://listmgr.nrao.edu/mailman/listinfo/difx-users">https://listmgr.nrao.edu/mailman/listinfo/difx-users</a><br>
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