On Fri, 28 Nov 2014 08:01:56 -0700, Jim Thompson
wrote:

On Thu, 27 Nov 2014 20:11:58 -0500, Martin Riddle
wrote:

On Thu, 27 Nov 2014 16:43:17 -0800, Robert Baer
wrote:

Jim Thompson wrote:
On Thu, 27 Nov 2014 18:14:07 -0500, Martin Riddle
wrote:

On Thu, 27 Nov 2014 11:20:38 -0700, Jim Thompson
wrote:

On Sun, 12 Oct 2014 12:45:29 -0700, Jim Thompson
wrote:

I need a SWAG on this, just to see if it's feasible...

Two inductors (solenoids) with Ferrite cores, each ~5mm in diameter
and separated by ~5mm spacing.

What coupling coefficient might I expect?

(Essentially no load on the "receiving" inductor except natural
losses... and I could tune or not.)

...Jim Thompson

Customer built a PCB and is getting good data coupling out to 2"
spacing.

Both ends are tuned with Q~10, so I'm going to cut it back a bit, I
fear cross-talk issues when he implements multi-channels.

...Jim Thompson

Can he put alternate channels on the opposite side of the board?
Or maybe a EMI shielding enclosure, might cause a change in the
inductance of the coil a bit.

Cheers

Customer has 1' PCB panels... Single inputs on N and W sides, outputs
on E and S sides.

...Jim Thompson
Sheet of mu metal placed at 45 degrees?
Stuff is rather good even at 60Hz and would get better as frequency
goes up.
Tie sheet to system ground plane, natch.

I've seen FM radios with a small single wall shield next to inductors
to break up the field. As long as the inductors are mounted 90deg from
one another coupling is at a minimum. I vaguely recall coils are
needed, so toroids are out of the question.


Cheers

http://www.analog-innovations.com/SED/MagneticDataCoupling.mov

...Jim Thompson

Oh I see now. Spooled inductors are wonderful emitters. Yep a lower Q
and I'd imagine separate TX and rx frequencies.
I believe there is specific EMI limits for intentional emitters if he
eventually goes for some type of certification. It could be either be
bad or good

Cheers