[morzh]

First of, Jph, injecting if freq. in antenna is not supposed to produce any tone. Antenna is connected to the RF amp an the tuned circuit will only let through the frequency it is tuned to. In prder for the IF to prduce the tone you need to feed it to the input of the IF filter, or output of it, that is the detector input.
This is why radios are tuned to stations' freqs.

Should've said that earlier when it was first suggested to you.