tda9800

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fairy
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tda9800

Post by fairy »

Hi i am looking for a way to tune the frequency i-e coming from phillips tda9800 tuner module. Any suggestions on how one can achieve this?

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Benj
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Re: tda9800

Post by Benj »

Hello,

I've not done this type of thing for a while but it looks like there are external components to allow you to tweak the VCO (voltage controlled oscillator) output.

fairy
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Re: tda9800

Post by fairy »

Thankyou benj,

can you share an example please, i am still confused.

Bestest Regards :)

fairy
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Re: tda9800

Post by fairy »

D i only have to give a pwm signal in order to tune the channel?

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Benj
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Re: tda9800

Post by Benj »

It looks to me like the VCO is tuned using a variable inductor and parallel capacitor.

You would probably either need a way of physically turning the existing variable inductor (servo motor?) or electrically recreating the variable inductor using say a multiplexer IC and lots of little inductors chained together in a R2R DAC type formation.

I would probably go with the first option to avoid the complications of the second option.

Just had a quick search and it does look like you can get digitally controlled inductors
https://www.google.co.uk/search?q=digit ... PGXvu1u_gO

fairy
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Re: tda9800

Post by fairy »

is that how they do it in television sets too?

and you are awsome.......:)

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Benj
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Re: tda9800

Post by Benj »

Thanks very much :D

In an old TV they probably have the tuning knob be a rheostat, this will effectively work as a potentiometer and a variable inductor. It's probably the variable inductance that controls the carrier frequency.

I studied a lot of TV, satellite and marine comms systems in college so my memory is hazy but I remember the old analogue systems being very well designed, field maintainable and bomb proof. Nothing like these botched together disposable digital systems we have today :wink: Saying that, tech is currently moving at such a rate that it probably needs to be.

fairy
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Re: tda9800

Post by fairy »

Hi Benj,

I did some research on the topic and i find this project very complex yet very interesting at the same time. I am confused in selecting parts for processing input frequency for UHD results? Can an avr or microchip will be able to handle all of this? Some body told me that i need about 10Gig for HDMI output :?: . Can i bring Flowcode 7 in action for this project :?: ? i see an RF component in an earlier version of FC. Please advice

Thank you :)

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Benj
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Re: tda9800

Post by Benj »

Hello,

A powerful 16-bit PIC can just about handle driving a 600 x 480 VGA output. At UHD resolutions you're talking super fast parallel processing such as a FPGA device. A microcontroller won't cut it at all. Video is a harsh mistress and requires dedicated bespoke silicone to drive it. For UHD you probably need something with the processing power of a modern graphics card. e.g. hundreds of parallel processor cores. The old analogue systems were really clever because they didn't have the processing power available but yet the analogue way it was put together allowed the data being received to drive the electronics. E.g. the front and back porch synchronised and controlled the timing of the electron beam. This was really clever but it was a really tiny fraction of the data of a UHD display.

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