Description:

This circuit serves two purposes; A mixing, B another IF stage increasing the receivers selectivity; because of the special design of IF 301, it will be off frequency if you put a capacitor from the emitter to ground, and will not be able to tune to 455KHz.

Build IF's 1,2,3, as close together as possible!

Testing:

Connect a signal generator to "RF IN", and an oscilloscope to the output,  sweep the signal like the last IF's around 455KHz; it should peak.

Alignment:

Set the signal generator at 455KHz and adjust the core for peak waveform like in IFs 2 and 3.

Note:  You will get a very weak signal from this stage because this part really does not need much amplification.

In circuit:

Connect the output of this circuit to the input of the second IF stage; realign all stages for peak waveform.

Note:  You may have to put a 22pf capacitor on the signal generators probe to "RF IN" in order to keep the circuit to keep it from modulating or canceling the signal out.  (or you can reduce voltage)

Note:

A common misconception when building mixers is that they just mix the two signals together, this is not true, there must be gain when the intermediate frequency is hit.