In the time befor VNA’s were invented there were instruments to measure things like antennas at high frequencies. General radio made this ” bridge” for that purpose. It is not realy a bridge but because it uses a zero detector, it looks like it is.
Thanks to Gerard , a GR collector, I finally have an Admittance meter.
It is a very nice build instrument.
And build in a very cute box.
You need a lot of things top use it. Two unit generators, the mixer, cables, a variable reactance and things like a short and load, linestretchers ect. Here you see a set up.
It is not a bridge. There is a voltage source that feeds 3 loops. If all is equal the signal currents cancel each other. For that the bidge is connected to a variable reactance, a fixed resistance, a generator, detector including mixer and LO, and the DUT, for instance a component or an antenna. The bridge gives admittance Y and split up in conductivity G and susceptance jB.
Variable capacitor 14-70 pF.
This cup is made to measure components in a shielded holder. The thing on the chain is a short you can mount in the middle position instead of the banana bus.
