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kalee20 · 22nd Apr 2021, 10:06 pm

Ever Ready 5033 is such a radio - 3-gang tuning capacitor which uses two sections for RF bandpass filtering (at least, on LW and MW. SW takes the aerial input to the second section of the filter).

The IF of this radio is 455kHz.

I don't know how good the tracking is, I'm not in a position to assess it right now - but certainly a single tuned circuit can cause tracking compromises. The adjacent channel selectivity all comes from the IF amplifier, whereas immunity to spurious responses, image frequency etc all has to come from the front-end signal tuned circuit. And if it is sufficiently selective to do this, it may well result in sideband cutting, or mistracking, whereas a bandpass filter with a response 20kHz wide will be easy to track, yet give superior attenuation beyond its passband.

22nd Apr 2021, 10:06 pm	#5
kalee20 Dekatron Join Date: Feb 2007 Location: Lynton, N. Devon, UK. Posts: 7,082	Re: Where is the RF amplifier? Ever Ready 5033 is such a radio - 3-gang tuning capacitor which uses two sections for RF bandpass filtering (at least, on LW and MW. SW takes the aerial input to the second section of the filter). The IF of this radio is 455kHz. I don't know how good the tracking is, I'm not in a position to assess it right now - but certainly a single tuned circuit can cause tracking compromises. The adjacent channel selectivity all comes from the IF amplifier, whereas immunity to spurious responses, image frequency etc all has to come from the front-end signal tuned circuit. And if it is sufficiently selective to do this, it may well result in sideband cutting, or mistracking, whereas a bandpass filter with a response 20kHz wide will be easy to track, yet give superior attenuation beyond its passband.