Hi all.
How can carrier presence be detected on a FM receiver with a TA2003 chip? Any simple add-on circuit that will turn on a LED for an active channel, if no pin in the IC is useable for that ?
-NOT carrier demodulation; unmodulated carrier detection-

 

How can carrier presence be detected on a FM receiver with a TA2003 chip

There is no direct pin in this chip.
Will the signal you need to detect always unmodulated?
I believe a noise operated squelch would be best.
You take the output from the detector and feed it through a high pass audio filter and convert the noise to a DC voltage. When a carrier is present the DC voltage will drop and trigger a comparator circuit to light a LED.
SG

 

Thanks, SG.
Goal is detecting carrier presence regardless of modulated or not, most times will be silent.
I wish there was a chip like the NE567 for RF... or IF 10.7 MHz.

 

Thanks, SG.
Goal is detecting carrier presence regardless of modulated or not, most times will be silent.
I wish there was a chip like the NE567 for RF... or IF 10.7 MHz.

As SG was saying..... With no signal in, the output of an FM detector will have a lot of noise - interstation hiss. Assuming there is a bit of gain in the chain. When a carrier is detected, the noise output of the FM detector will drop dramatically - this is the 'quieting' spec. Modulated or not makes no difference.

At the detector output, connect a high pass filter/amp/rectifier and you will see a DC output when there is no carrier, and a drop in that DC when a carrier is detected. As long as your HPF is appropriate, then modulated or not makes no difference.

 

Thanks.
Will explore your suggestions. Ordered AD8307 chips to evaluate if can detect at the IF signal pin. At least I will learn something else experimenting.