Cross Modulation in Transistor Tuners

Abstract

This report compares the cross modulation of transistors and tubes in a HF tuner. The results substantiate the theory developed by several authors and indicate that transistors are about 1 1/2 to 2 times worse than tubes. However, it is shown that by using small degenerative emitter resistors, the transistor can be made as good as the best tubes. In fact, by using a 56 ohm unbypassed emitter resistor and forward AGC the cross modulation of a T-2028 MADT is equal or better than the best tube tuners over the entire AGC range.