OT: This Swift thing

[Gene Heskett]

On Thursday 12 June 2014 13:18:00 Chris Angelico did opine
And Gene did reply:
> On Fri, Jun 13, 2014 at 3:04 AM, Steven D'Aprano
> 
> > I'm saying that, whatever the practical engineering limits turn out
> > to be, we're unlikely to be close to them, and therefore there are
> > very likely to be many and massive efficiency gains to be made in
> > computing.
> 
> And this I totally agree with. The limits of physics are so incredibly
> far from where we now are that we can utterly ignore them; the limits
> we face are generally engineering (with the exception of stuff
> designed for humans to use, eg minimum useful key size is defined by
> fingers and not by what we can build).
> 
> ChrisA

Thats a bit too blanketish a statement, we do see it in the real world.  
Some of the electronics stuff we've been using for nearly 50 years 
actually runs into the e=MC^2 effects, and it affects their performance in 
pretty deleterious ways.

A broadcast power klystron, like a 4KM100LA, which is an electron beam 
device that does its amplifying by modulating the velocity of an electron 
beam which is being accelerated by nominally a 20,000 volt beam supply.
But because of the beam speed from that high a voltage brings in 
relativity effects from e=MV^2 mass of the electrons in that beam, an 
equal amount of energy applied to speed it up does not get the same 
increase in velocity as that same energy applied to slow it down decreases 
it.  This has the net effect of making the transit time greater when under 
high power drive conditions such as the sync pulses of the now out of 
style NTSC signal.  The net result is a group delay characteristic that is 
uncorrectable when the baseband video is where you are trying to correct 
it.  In a few words, the shape of the sync signal is damaged.  Badly.

Because most transmitters of that day used separate amplifiers for the 
audio, and the receivers have used the 4.5 mhz difference signal to 
recover the audio in the receiver for the last 63+ years, this "Incidental 
Carrier Phase Modulation" noise is impressed into the detected audio.  And 
I am sure that there are many here that can recall back a decade that the 
UHF stations in your area, all had a what was often called "chroma buzz" 
in the audio that was only about 50 db down.  Ear fatiguing at best.  
Market share effecting too.  And that translates directly into station 
income minus signs.

It was fixable, but at an additional cost in efficiency of about -20%, but 
consider what that 20% costs when a station using a 30kw rated 
transmitter, actually pulls around 225 kwh from the powerline for every 
hour it is on the air.  Bean counters have heart attacks over such 
figures.

Cheers, Gene Heskett
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