Usually the detection efficiency is more less than 90%.
Signal through the detection is over 10%. And AF UNIT gains about 40dB. Non detected signal(boosted) makes whats ?
Somtimes occurs feedback oscillations.
Already you've known that.
On transistor radio kits , 'in-put' and 'out-put' transformers in AF UNIT success to cut off of IF signal.They have frequency characteris,so gain 455kc just a little.
We often get OTL radio kits. And ITL radio kits. How about ?
LPF After IF stage is must . The cut off point is important. And decide the cut off point so as not to feedback oscillations.
The is notice when making radio kits all ways.I think so.