On 11/4/2015 10:31 PM, Jeff Liebermann wrote:
On Wed, 4 Nov 2015 21:24:55 -0500, rickman wrote:


I seem to recall some errors were reported, but I don't recall them
being of any consequence.

You haven't indicated if it's your model. I uploaded it to:
http://802.11junk.com/jeffl/antennas/magnetic-loop/Antenna_trans_LTspice/Antenna_trans_loop.asc
Is this the latest? This is what it produces:
Circuit: *
C:\blah-blah\jeffl\antennas\magnetic-loop\Antenna_trans_LTspice\Antenna_trans_loop.asc
Number of points per octave reduced from 3000000 to 19545.
Multiply defined .measure result: max
Each .measure statement needs a unique result name.
Date: Wed Nov 04 16:49:57 2015
Total elapsed time: 0.266 seconds.

Yes, I wrote the simulation with help from a variety of sources. The
above is not really an error. Just reduce the number of points used. I
don't recall how that is set, but much of it is parametrized.

I'm not sure what is up with the MAX error report. That sounds like a
problem with a line continuation.

That was the .ac directive. Too many points per octave.

Here's my tweaked version of the loop. No errors this time:
http://802.11junk.com/jeffl/antennas/magnetic-loop/Antenna_trans_LTspice/Rickman_60KHz_loop_02.asc
Screen grab of the output:
http://802.11junk.com/jeffl/antennas/magnetic-loop/Antenna_trans_LTspice/Rickman_60KHz_loop_02.jpg

What I done did:
1. Removed all the .MEAS stuff that was producing errors. Just put
the probe on the "output" line.
2. L1 and L2 were over coupled. I reduced the coupling from 1 to
0.02. I intentionally did NOT overlap the resonant peaks so the
tuning is slightly off. It's fairly close to critically coupled.

Why is this over coupled?


3. Adjusted C1 and C2 for 60 KHz tuning.
4. Change frequency axis (.ac) parameters.

I like to have a major tick at the frequency I am interested in, 60 kHz
in this case.


5. I got lazy and didn't add the usual title block stuff.
6. There are no values for Rs which needs to be considered.

What is Rs, the loss resistance? Hmmm, this must have been an older
copy, I am sure I included that, possibly in one of the coils since that
is what it is from. I'm not sure I included radiation resistance as I
barely knew what that was. I recall someone said it should be in there
and gave me a rough value which was very small. I now understand it
better and the calculated number is 2.669E-010 ohms, so obviously it can
be totally ignored.

My real circuit had some other components at the output that complicate
the real circuit. The "receiver" is an FPGA with a very high input
impedance. To bias the input to the threshold of the input there is an
output of the quantized value which is filtered by an RC circuit and
used to bias the other side of the CT secondary rather than grounding
it. I haven't decided on the exact circuit for the digital side.

--

Rick