[SI-LIST] Re: loop antenna (mis)behavior
- From: Gene theBean <mosfet_the_gr8@xxxxxxxxx>
- To: si-list@xxxxxxxxxxxxx
- Date: Tue, 3 Jun 2008 09:07:48 -0700 (PDT)
Hi Orin,
Sorry if I never replied about the metal shielding around the loop (it's
possible I replied directly to a post). No, it's not grounded, by design, and
is not likely to be in the future so I have to reluctantly live with that. On
my test antenna, I had tried a grounded sheild around the RX antenna, a small
gap, and found the signal penetrated with no loss. No gap at all results
in complete loss of signal.
Remember, though, my circuit actually fixed the problem completely. At least,
on my test sections and bench circuit. It will be tested on the actual device
within the next couple of days, so stay tuned.
This forum really helped me to understand the mechanisms responsible for how
this loop antenna stuff works - thankyou! At this time, I believe the problem
really comes down to how I was processing the received signal at the loop.
Eric mentioned this too, as I recall. Unless the signal is looked at in a
differential mode with current flowing, you won't see the phasing. As Eric
mentioned, if the scope is in 10 Meg mode, there's no current flowing, and you
can only see the common mode stuff (presumably from e-field/capacitive
coupling) - and that is how I was measuring it. The original circuit suffered
from the same problem. The new circuit fixed it. I thought people would be
interested.
gene
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