12-07-2013, 11:39 PM
The low impedance loop of the 1941 and later sets eliminated the need for the electrostatic shield by virtue of its design. Because it consists of only a few turns of very heavy wire, it presents a very low impedance to electrostatic fields, effectively shorting local interference to ground.
In order to bring the desired radio signals back up to useable level, the low impedance loop is connected to a step up tuned transformer in the mixer grid circuit, matching to its high impedance. In this way, interference rejection is achieved without the electrostatic shield and sensitivity comparable to the previous multiturn loop is maintained.
The low impedance loop and the low noise XXL triode mixer were real innovations that were far ahead of the conventional front end designs of the time.
In order to bring the desired radio signals back up to useable level, the low impedance loop is connected to a step up tuned transformer in the mixer grid circuit, matching to its high impedance. In this way, interference rejection is achieved without the electrostatic shield and sensitivity comparable to the previous multiturn loop is maintained.
The low impedance loop and the low noise XXL triode mixer were real innovations that were far ahead of the conventional front end designs of the time.
