Well, remember that all protons are not identical and one must use the
'magic individual combination of RF freq and field strength' to get a proton
to flip.
That simply means oine could keep the field constant and vary the RF freq or
keep the RF freq constant and vary the field. Really doesn't matter to the
protons but one way may be much, much simpler to implement than the other.
BTW the percent change in one or the other is small e.g. about 0.1 % would
cover all protons.
----- Original Message -----
From: "David McClafferty" <ve1adh@yahoo.ca>
To: <tentec@contesting.com>
Sent: Friday, December 12, 2003 15:22
Subject: Re: [TenTec] Induction Field [WAS - PS grounding]
> I thought it was just the RF field that was changing
> within a steady magnetic field. Did some more reading
> and found there is a smaller magnetic field that is
> pulsed.
> I was wondering what the RF frequency was. It doesn't
> seem to be mentioned in anything I have read.
>
> Dave
>
> --- Ken Brown <ken.d.brown@verizon.net> wrote: >
> David McClafferty wrote:
> >
> > >To induce a current into a conductor the magnetic
> > >field must be varying or the conductor or field
> > must
> > >be moving. The magnetism in an MRI machine is
> > steady,
> > >so unless they wheeled you in there quite fast, you
> > >wouldn't get much current induced into your body.
> > >
> > >
> > Excuse me, but if there is no change in the field,
> > it will not make
> > anything resonate. I'll look at the url you included
> > later and see what
> > they say. If they say that it is a constant, non
> > varying magnetic field,
> > then I say they are wrong. I took my VX-5 handheld
> > radio and listened
> > outside the lab while my wife was in the MRI
> > machine. And I heard lots
> > of varying pulse rates and bandwidth signals around
> > the 60 MHz area.
> > What I heard defininately came from the MRI machine,
> > and it is not
> > surprising that water molecules have a resonance
> > around 60 MHz, human
> > bodys being mostly water. Also the spare 3CX800A7s
> > that I have for my
> > Titan 425 are pulls from a MRI machine. If it was a
> > constant magnetic
> > field and not a varying one (at RF frequencies where
> > ther are resonances
> > with things in the body) they could just use a
> > switch of some sort and
> > not need a power amplifier tube>
> >
> >
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