digital dial display

Your circuit is basically a counter/timer circuit, fed from the radio tuner tank circuit. Your timer/counter will be have to be fed from a crystal based oscillator which operates at at least 4 times your highest frequency in order to have reasonable accuracy. Some level of signal conditioning will be required to get your analog tuner output to the right level to work with digital counters. And it will have to be high impedance so as to not overload the tuning circuit and spoil your ability to receive a broadcast signal.

In general, it takes some manipulation to mix analog and digital circuits effectively. If you actually pursue this idea, I would expect you to want to salvage the timer/counter device for other projects which you will find to be of greater importance than a radio display. Timer/counters are a basic measurement device like a voltmeter or oscilloscope. Consequently parting with one of these for a dedicated purpose is difficult. Drift or variation in the "reading" or display will be normal and you may find it distracting.

Newer radios synthesize the tuner circuit from a higher frequency oscillator used to run the digital clock of the device. Consequently, it already knows the effective frequency since it has to divide its clock frequency by some number to get the synthetic tank circuit frequency. By its very nature, a digital display is easy to apply because it already has all of the required information. Drift is not noticed in a digital device because it is not really measuring anything for the display.

I think you may find it a better use of your to time to just buy a digital radio and leave the analog radio alone. Interesting idea but not very practical.

Thank you

EUROPA1930

I think you need a frequency counter for your old radio, try to type "radio freq counter circuit diagram" at google search bar, you'll found some circuit diagram of frequency counter for your old radio.

Generally, the super heterodyne radios use:

Radio frequency amplifier for the 500KHz - 1600KHz medium waves AM (has anybody ever heard of long waves?)

4MHz - 30 MHz different classes of Short waves (still AM) and 88 MHz to 107MHz for FM.

When you tune on your proffered radio-station, say 1000KHz, this frequency is mixed with the frequency of the local oscillator which, for this station is 1465KHz (local oscillator frequency is, always 465KHz higher than the received station). From the resultant, sum and difference, one choses the difference, which is 465KHz. This is the intermediary frequency that is, further amplified, demodulated, and audio amplified.

If you want to display numerically the frequency of a station, your best bet, as voltage to convert to digital, would be the local oscillator frequency. But this is 465KHz higher than the real one, so your counter has to have an offset of 465. If you amplify the RF enough, than you can measure directly that frequency.

I think that you better replace the analog guts of your radio with digital ones (with a poorer selectivity and sensibility, though).