Using TV Tuner as front-end for Communication Receiver

[abasir]

I came across the following site (https://hem.passagen.se/communication/supertuner.html) using TV tuner as communication receivers. The tuner mentioned is difficult to source now. With the availability of cheap TV cards for the PCs (with built in tv tuner outputting video and audio directly), can the following be done (the tuner will be removed from the PCB and controlled directly with microcontroller/PC using I2C) :

TV Tuner Video Output --> Mixer (with DDS LO) --> 455kHz filter --> Demodulator (FM, AM, CCW, etc) --> Audio.

The main reason for the hack is to allow 1Hz resolution to frequency change. Most tuners only allow 50kHz resolution.

Thanks & regards,

 

[IanP]

I don't think you can do it this way.
The output from TV tuners from computer cards is the baseband video signal (after AM-demodulation) and will be usless for you.

 

[cozturk]

Fine tunning can be useful for Audio IF stage. So we can step in 50kHz step. For FM radio mode, tuner's step can be made 31kHz. and it can be reduced for changing 4MHZ xtall to 3.58MHZ also.

Of course we can take IF signal from mixer IC to AM demodulating and for our narrow band IF stage. Perhaps A cheap AM/FM radio can be used. I tried it for FM demodulating. Successful. But AM not tested. Radios LO should be tunned for 30 MHZ .

 

[abasir]

I don't think you can do it this way.
The output from TV tuners from computer cards is the baseband video signal (after AM-demodulation) and will be usless for you.

Thanks for highlighting the above to me. I'll pry open the tuner module and take the VIF output for the task. Any good site describing TV tuner operations? I've always been 'digital' so this RF stuff is not my domain

 

[abasir]

Gurus,

Could I use the intercarrier signal instead of the VIF? The tuner I have uses TDA9801 that output video/audio intercarrier. I plan to use the intercarrier, mix it with DDS signal and feed the output to the 5.5MHz filter and FM demod unit of the TDA9801. Don't want to redo the circuit already there

Thanks