b32. Drake TR-4/TR-4C
b31 1-A, 2-A, 2-B
Drake TR-4 mod.
The receiver has too little audio gain, particularly a problem on the higher bands when signals fade out.
TR-4C is improved in this respect, so it is just to copy the extra audio amplifier used for TR-4C using almost
anything of a general purpose transistor like BC237, MPS3394, 2N2222, 2N3877, 2N3904, 2N4401 and
many more. The circuit must be constructed such that the voltage over the transistor is limited to what it
can stand, usualy it is so low current that it is no problem. But the voltage cannot reach such high voltage
when the circuit is properly constructed. It is no need for voltage regulator or zener diode
Because of relative high current gain and that R3 is not decoupled makes a high input impedance