I cannot see any real problems putting the coil on the board, but I wouldn't
mind betting it will take more turns than a remote (wire) coil to get it to the
same resonant frequency (inductance). (Due mainly to the coils self capacity to
its (own) other windings. You need to either simulate the resonant frequency, or
test a few boards to get this right! Since a prox card antenna is usually driven
in series resonance, you need to get the tuning reasonably close before the
antenna works particularly well. (But you can alter the series capacitor to get
into tune), so all is not lost!)

Use the Inductor designer mentioned in other threads if it will estimate an
inductance.



Cheers
Harry

Home office phone (03) 9504 1957
[EMAIL PROTECTED]




-----Original Message-----
From: John C. Echols [mailto:[EMAIL PROTECTED]
Sent: Monday, March 29, 2004 6:32 AM
To: [EMAIL PROTECTED]
Subject: [PEDA] Antenna coil

I'm the guy still using Protel 1.61 (1992) with Windows 3.11 and I'm on
a phone line....now that you're through laughing my question is - my
present project requires a coil for an antenna for a "prox" card
reader.  The coil is about 3.25 X 4.25", 700uHy and takes 60 turns of
mag wire.  Can I do this with traces? The easiest would be 30 turns on
one side and one via to do 30 on the back.  I'd probably go .004/.004"
so it's not too hard for the board house and would only take .24 width
of board space.  Will this work or is the spacing too big?  Or do I need
to do one turn on top, the next on bottom, next on top, etc?  All the
vias would take up too much room.

Thanks for the help.

John Echols





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