Re: [LAD] Wireless Electricity vs audio quality

On Monday 25 August 2008, Dan Mills wrote:
>On Mon, 2008-08-25 at 09:38 -0400, Fred Gleason wrote:
>> I can sure vouch for the truth of this. Been in enough high-power
>> broadcasting plants (>=50 kW) at both MW and FM frequencies to see it lots
>> of times. It can be a real bugbear, especially with consumer or even
>> semi-pro gear.
>
>Even some seriously pro gear gets it horribly wrong on occasion, and
>designing it right is a pain as what works at 500Khz, generally does not
>at 1Ghz and stray resonances can scupper even the best filters over that
>sort of bandwidth.
>
>Now it can be done, as (at the third attempt) I have a multichannel
>audio board that just works even in the presence of significant power at
>AM broadcast, FM Broadcast, 900Mhz and 2.4Ghz, but it took some doing
>(The hardware is likely to go for well over £500 per card, and about a
>third of that is parts cost).
>
>We will gloss over the AM site I had co located with a bloody search
>radar on an army base that was FUN to get to work right.
>
As is a modern digital satellite receiver or a tv stl in the 2.1Gig band, when
its 17 air miles from a 50 megawatter at the local airport. An analog rx
shows a black dot occasionally, but the digital stuff upchucks all over
itself. The filters to fix it are a bit over a kilobuck each.

>Wireless power transmission by low frequency resonant coupling **IS** a
>useful trick in some circumstances (I have seen it used to charge hand
>lamps for use in explosive atmospheres for example (Well over ten years
>back)), and in intels case could be used to for example power a wireless
>mouse or charge a phone, but you can bet there would be a handshake
>between the device and the charging pad prior to RF being applied. It
>will never work well over any distance as the inverse square law applies
>once you are out of the near field of the aerial (A tuned loop from what
>I can see - also very old technology), this distance depends on both
>wavelength and loop dimensions, so making the loop smaller will not
>improve things).
>
>It is not a viable replacement for a power cord for anything that needs
>more then a watt or so or that is reasonable mobile, but I could maybe
>see it for things that can be placed on some sort of pad (And yes, RF
>pickup will be a real and serious problem).
>
>Regards, Dan.
>
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-- 
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)
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our ancestors.
		-- Plutarch
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