Let’s put this on the agenda for tomorrow. We could keep as is, except put in 25m everywhere we can (so have 25m and 35m)…
Dave > On Apr 12, 2016, at 2:22 PM, Nithyanandan Thyagarajan > <[email protected]> wrote: > > Part of me favors having one cables of one kind (it this is an option) than > two - better to lose one mode than two besides other complexities which we > may not fully grasp yet that come with multiple cable lengths. > > From: <[email protected] > <mailto:[email protected]>> on behalf of DAVID DEBOER > <[email protected] <mailto:[email protected]>> > Date: Tuesday, April 12, 2016 at 1:54 PM > To: danny jacobs <[email protected] <mailto:[email protected]>> > Cc: hera <[email protected] <mailto:[email protected]>> > Subject: Re: cable lengths > > I was going to suggest the same thing. We could have an ‘active’ long cable > (i.e. a pre-post-amp right at the balun). And how long do we need — 150m is > already uncomfortably long… > >> On Apr 12, 2016, at 1:50 PM, danny jacobs <[email protected] >> <mailto:[email protected]>> wrote: >> >> What about making most of them short and then some of them really long? >> >> On Tue, Apr 12, 2016 at 1:49 PM, Adam Beardsley <[email protected] >> <mailto:[email protected]>> wrote: >>> My concern would be pushing any cable reflection contamination to modes in >>> the window. Currently only a small subset of MWA antennas have 150 meter >>> cables, but the reflection line shows up very clearly. 45 meters puts the >>> delay right at 0.2 h/Mpc, which is where we do a lot of our sensitivity >>> forecasts. I doubt moving to 0.3 would change sensitivity much, but just >>> food for thought. >>> >>> -Adam >>> >>> On Tue, Apr 12, 2016 at 1:26 PM danny jacobs <[email protected] >>> <mailto:[email protected]>> wrote: >>>> The 35m length has been worrying me a little lately. Would there be any >>>> downsides like having a different spectral response for the longer cables? >>>> >>>> ~D >>>> >>>> On Tue, Apr 12, 2016 at 1:24 PM, DAVID DEBOER <[email protected] >>>> <mailto:[email protected]>> wrote: >>>>> Hi - I was thinking about the analog cable lengths a bit. We have a spec >>>>> at 35 m (30m+the vertical part to the feed). This puts the delay at >>>>> about 0.15h/Mpc. Would it be advantageous to have, say, most of the >>>>> cable lengths at 25m and a smaller subset at 45m? >>>>> >>>>> Dave >>>> >>>> >>>> >>>> -- >>>> ================================================================ >>>> Daniel C. Jacobs >>>> KE7DHQ >>>> National Science Foundation Fellow >>>> Arizona State University >>>> School of Earth and Space Exploration >>>> Low Frequency Cosmology >>>> Phone: (505) 500 4521 <tel:%28505%29%20500%204521> >>>> Homepage: http://loco.lab.asu.edu/danny_jacobs/ >>>> <http://loco.lab.asu.edu/danny_jacobs/> >>>> MWA: mwatelescope.org <http://mwatelescope.org/> >>>> HERA: reionization.org <http://reionization.org/> >>>> PAPER: eor.berkeley.edu <http://eor.berkeley.edu/> >> >> >> -- >> ================================================================ >> Daniel C. Jacobs >> KE7DHQ >> National Science Foundation Fellow >> Arizona State University >> School of Earth and Space Exploration >> Low Frequency Cosmology >> Phone: (505) 500 4521 >> Homepage: http://loco.lab.asu.edu/danny_jacobs/ >> <http://loco.lab.asu.edu/danny_jacobs/> >> MWA: mwatelescope.org <http://mwatelescope.org/> >> HERA: reionization.org <http://reionization.org/> >> PAPER: eor.berkeley.edu <http://eor.berkeley.edu/>
