Balanced antenna receiver antenna desgin question |

Balanced antenna receiver antenna desgin question

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I'm looking for ideas on how to improve an existing design that is giving us problems with regards to coil antenna length and noise. We use wire wound coils as transmit and receive antennas, but with the longer coil lengths >70 inches, we have an issue where the system is sensitive to capacitive contact from the hands. Any ideas on how to go about isolating a design problem that I didn't design would be great. The signal is a bipolar 2100 Hz pulse that is received and uses eddy current to detect metal. It seems to be a problem with our digital systems, as our analog systems don't seem to present the same problems.

Any ideas would be greatly appreciated.

Discussion started by Mike Burr , on 17 December 08:45 AM

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Mike Burr, 2009-12-29 08:53:57

To add some more information to the equation. After looking at some of the antenna information, it looks like the inductance sets the resonance to less than a quarter wave. It may be enough to cause a standing wave back into the system which shows up as noise. adding an inline inductor with the transmit antenna seemed to abate the noise back into the system. This isn't an end all solution. I know for the most part with digital communications etc. the concept of impedance matching for power has been lost, to where we now match for effective voltage transfer. But how does one go about matching impedance of a digital system where the old analog rules still need to be applied?