12-06-2012, 06:50 PM
Hi Al, been roofing hence David beat me to it, he has described it well, as far as I am aware and can remember you can null R by using the pot and null the reactance (+j -j) using the variable capacitor, both of these controls are incorporated in the noise bridge, once the values are read off then a maths calc. will give the impedance (we now know the maths so should be easy) Loads of designs on the web, zenner plus a couple of transistors and a few passives. If a tuned calibrated null detector was built into it say using a meter then a receiver would not be required as the null indicator, would make a nice instrument at reasonable cost.
Lawrence.
Lawrence.
