ITs cleverly hidden...
T1 and R4 and 3/4ths of the bridge the antenna is the other leg. The centertap of the
transformer will have zero RF(noise) if the antenna leg has the exact same resistance
and reactance as R4. What most expect to be resistors are the two halves of the
trifilar wound (three identical windings) transformer.
If R4 is made variable you can measure the impedance in the other leg. The Palomar
(and others) device adds a variable capacitance to allow measuring the reactance
as well. When R,jX are equal to the other leg then you can directly read it from a
For interest or if you plan to make on two articles one for the Palomar and another
on building and using.
The noise bridge was the pre-MFJ-259B device that was available and