paulears Posted July 17, 2012 Share Posted July 17, 2012 In Tv-Bay this month there was what looked like an interesting article on Time Domain Reflectometry. It used examples of coax cable in 75 and 50 Ohm versions. However, the text suddenly changed from talking about Ohms and started using Watts - references to 75, 50 and 110 Watt termination resistors. It also talks about changing the termination resistor from 75W to 74W and referring to drawing 2 which clearly shows R2 as being 50R or 110R, not 75R. It talks about using appropriate test pulses of 16,32 or 64nS - but then talks about and shows a picture of a slight dip in a waveform display of the effect of adding a 100mm stub - referred to as 'tiny' - 100mm isn't exactly tiny, so should this be 10mm? I wanted to understand this properly, to be able to see the effects of mismatch, and I think I've worked it out - but whoever proof read it surely needed to spend a bit more time checking the content. Link to comment Share on other sites More sharing options...
pjb304 Posted July 17, 2012 Share Posted July 17, 2012 I've seen W used instead of Omega before. According to wikipedia it's a common thing, but very confusing. Link to comment Share on other sites More sharing options...
DrV Posted July 17, 2012 Share Posted July 17, 2012 In Tv-Bay this month there was what looked like an interesting article on Time Domain Reflectometry. It used examples of coax cable in 75 and 50 Ohm versions. However, the text suddenly changed from talking about Ohms and started using Watts - references to 75, 50 and 110 Watt termination resistors. It also talks about changing the termination resistor from 75W to 74W and referring to drawing 2 which clearly shows R2 as being 50R or 110R, not 75R. It talks about using appropriate test pulses of 16,32 or 64nS - but then talks about and shows a picture of a slight dip in a waveform display of the effect of adding a 100mm stub - referred to as 'tiny' - 100mm isn't exactly tiny, so should this be 10mm? I wanted to understand this properly, to be able to see the effects of mismatch, and I think I've worked it out - but whoever proof read it surely needed to spend a bit more time checking the content. At propagation speeds of (very very roughly) 2nS/foot in eg ribbon cable, 100mm represents about 0.7nS so in the context of a 16nS pulse it is pretty small. But as the former company proof reader I get anoyed at that kinf of sloppines twoDave Link to comment Share on other sites More sharing options...
Junior8 Posted July 18, 2012 Share Posted July 18, 2012 and I think I've worked it out - but whoever proof read it surely needed to spend a bit more time checking the content. If it was proofed at all! I do my level best to send in correct copy in the sure and certain knowledge that very few people can proof their own stuff fully. I don't think in 90% of cases these days it's ever looked at again. Link to comment Share on other sites More sharing options...
kerry davies Posted July 18, 2012 Share Posted July 18, 2012 Couple of mates used to write TV crits for the Grauniad and their Macs in Bristol were directly linked into the presses in wherever. Explains how one famous glitch saw the sex of the protagonists switched and much hilarity on HIGNFY. Spellcheck never picks that sort of thing up. Wit ewe awl them weigh, Dive. Productive sexed is two blame four moist of hit. Link to comment Share on other sites More sharing options...
sleah Posted July 18, 2012 Share Posted July 18, 2012 But as the former company proof reader I get anoyed at that kinf of sloppines twoDave Sorry Dave, but I DID actually :** laughs out loud **: at that. :P Link to comment Share on other sites More sharing options...
MarkPAman Posted July 19, 2012 Share Posted July 19, 2012 I'm pretty sure that was his intention! Link to comment Share on other sites More sharing options...
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