Re: [LAD] Wireless Electricity vs audio quality

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.

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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Received on Tue Aug 26 04:15:01 2008