friends, i want to make an project in my academics. i.e. MULTIBAND (AM/FM) radio with AUTO TUNNING. i know the design procedure for the radio circuit but i have no idea about the design of the auto tunning circuit that will scan both AM and FM bands. so please any body having any idea share with me.
thanking you
with regards Pradipta
use varactor diodes to take care of the capacitance tuning for the RF, VCO.
have station detector circuit that detects when tuned to the station.... (without false triggering).
Simple.
Joe
litu snipped-for-privacy@gmail.com posted to sci.electronics.design:
Simple, factor for the common parts versus the band unique parts and build it. Dithering will provide the autotuning information.
(Assuming analog transmission): It's not that simple. Use a PLL to tune the Local Oscillator to each frequency in the band. When the RSSI (received signal strength indicator) reaches a pre-determined threshold, stop at that frequency. Use a counter to count the I.F. This makes sure the received signal is on frequency. False stops are still possible but less likely.
If you don't have access to the RSSI signal, you will need to convert your I.F. signal amplitude to a log scale for the thresholding measurement.
This is how we did it in the late 80's.
Frank
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