I'm talking about frequencies usually used by commercial FM radio stations (80-110 MHz).
"Specific frequency" would seem to imply that a complete selective receiver is required and if the signal is in any way remote, a Field Strength meter is not going to "cut it".
It definitely sounds as if the TEA5767 or similar is the way to go.
Hi, if you are looking to measure signal strength, look at the radio receiver chip specs and look to see if it has a AGC or Automatic Gain Control. This pin will have a DC level on it either proportional or inversely proportional to the RF signal strength.
page 22, pin 38 Tagc, this looks like it has the agc voltage you need.
That could be it, I'll explore further. Thank you!