On Wednesday 16 April 2014 21:57:21 Simon Wise did opine: > On 16/04/14 23:20, Gene Heskett wrote: > > On Wednesday 16 April 2014 09:09:06 Simon Wise did opine: > >> I was shown a rather nice artwork that used high resolution radar > >> (resolutions around 1 centimetre I think) to get positions (it was > >> made in a university robotics department that had such things!). The > >> way those work is very interesting ... the frequencies are way to > >> high to digitise, so the electronics has to be all analogue ... the > >> 'circuitry' is basically plumbing ... gold lined tubes and chambers > >> using resonances and such to measure delays and phase differences. > >> At those frequencies the speed of light becomes a dominant > >> consideration. > > > > We have a gismo thats basically much simpler than all that plumbing, > > to use when checking a cable for damage, called a Time Domain > > Reflectometer. The pro versions using a tunnel diode switch as a > > pulse generator, can tell you theres a bullethole in the line 883.6' > > out from where you are hooked up. I've made homemade versions using a > > pulse generator and a fast oscilloscope to measure the echo delay, > > punched some buttons on a good calculator and then told the tower > > crew where to open it up and replace a burned up connector bullet > > and/or the teflon disk holding it centered in the line. It got the > > job done so I figured it was good enough for the girls I go with. :) > > not at all convinced that a fast oscilloscope, a good calculator and the > wet-ware connecting them are simpler than a bit of machined metal with > gold plating, but certainly re-using existing gadgets beats making new > ones. > Either method requires that the operator have intimate knowledge of the characteristics of the transmission line being measured. That is considerably more important then the cost of the tool, particularly when the results are adequate for the job at hand. When you are off the air, the cash machine is broken, and that was at least 2 days quicker than getting a TDR overnighted from Vegas when the rental check had to be in Vegas before the instrument is pulled off the shelf to send it. A case of time vs money lost. We actually had to pull it apart and clean up about 80 feet below the burnup because the soot from the burnup settles on the disks below it, encouraging the next burnup. Eventually that 40 YO line did get a full rebuild with Andrews new screwed together inners. End of problem, and now its off the air as we moved the tx when we made the digital switchover. So if anyone needs a 450 foot stack of Stainless G5, with a RCA TF3-AL antenna on top of it, with the rebuilt 3.125" lines, talk to me. But your crew will have to take it down & ship it. > > Simon > _______________________________________________ > Linux-audio-user mailing list > Linux-audio-user@xxxxxxxxxxxxxxxxxxxx > http://lists.linuxaudio.org/listinfo/linux-audio-user Cheers, Gene -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) Genes Web page <http://geneslinuxbox.net:6309/gene> US V Castleman, SCOTUS, Mar 2014 is grounds for Impeaching SCOTUS _______________________________________________ Linux-audio-user mailing list Linux-audio-user@xxxxxxxxxxxxxxxxxxxx http://lists.linuxaudio.org/listinfo/linux-audio-user
