View Full Version : FM Demodulator with Tv Tuner

12-16-2010, 01:39 PM
Hi All
I have a Tv tuner that outputs 38.9 mhz If signal. I want to connect
FM demodulator in front of it to receive Fm broadcast signals (88-108Mhz) as well as other transmissions. I have seen over the web at
fm demodulator but the demodulator IC MC13136 requires many external components as it converts the signal into 10.7mhz If. so as other ICs like FM radio receivers TDA7000 and LA1800.
Can any one tell me how to demodulate 38.9Mhz signal without conversion.
Is there any IC that can extract audio without converting it to 10.7Mhz.

12-16-2010, 04:38 PM
Both the 38.9 MHz and 10.7 MHz signals are IF frequencies. You do the demodulation after the IF stage.

I would suggest that any superheterodyne receiver is going to be as colplex as another, so trying to use the 38.9 MHz IF will require as much circuitry as the standard 10.7 MHz IF for FM broadcasts.

Is there any IC that can extract audio without converting it to 10.7Mhz.You may be able to find direct conversion IC's. You can look at this link - http://en.wikipedia.org/wiki/Radio_receiver_design

12-17-2010, 07:01 AM
Thanks for the reply,
Is there any IC i can use 38.9Mhz IF signal as Rf input, TDA7000 has RF input ranging from 70 to 120 Mhz but mine is 38.9Mhz.
Any ideas ? Is there any other IC that does't require Quad Coil for demodulation,discriminator/ PLL demodulator, that operates in the range that covers 38.9Mhz. I have heard of NE565 but it works in Khz.
Please Reply soon.

12-17-2010, 07:10 AM

On this page you will find a lot of information on the TV tuner:

This is a link from the EDUCYPEDIA on Television systems: