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How to make CATV Signal streght meter ?!

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csaba911

Member
I was thinking to create a RF signal strength meter from a dead VCR tuner. :idea:
Using a PIC or c51 to change the frequency and display it on the LCD.
I cant find any info how to control the tuner.

Any one have any experience with this :?:

Thanks
Steve
 

Nigel Goodwin

Super Moderator
Most Helpful Member
csaba911 said:
I was thinking to create a RF signal strength meter from a dead VCR tuner. :idea:
Using a PIC or c51 to change the frequency and display it on the LCD.
I cant find any info how to control the tuner.

Any one have any experience with this :?:

Thanks
Steve

There seems very little info available on the tuners themselves, you may have to open it up and find what PLL IC it uses, then try and find a datasheet for that.
 

pebe

Member
You need the complete RF section of the VCR. The tuner, IF stages and demod. If you can get hold of a circuit you will need to identify the AGC (automatic gain control) line. When a signal is received, the demod produces a voltage that is fed back to the RF and mixer stages in the tuner in order to keep the demod output at a constant level. The voltage produced will be a measure of signal strength.

That voltage can be amplified to a suitable level with an op-amp and fed to the A/D section of your microcontroller and programmed to give a display.
 

pebe

Member
Sorry! I've just re-read your post and realised I didn't answer your question.

I stated how to get the signal strength, instead of how to control the tuner's frequency. :oops:
 

csaba911

Member
Thanks for the info, its help a BIT. :p
The real mystery is how to make the tuner to change frequency, I GUESS is I2C or other serial protocol is used to change, I tied to change the tuner supply voltage "+30v", it is working but very ruff. I collected more than 10 VCR for this project, any specific brand is better than the other tuner?
I think most of the tuner has the RF and IF on the same board.

It is not a stone age VCR's, 1-4 years old..

Anything else you can help, PLEASE...

STEVE
 

Nigel Goodwin

Super Moderator
Most Helpful Member
csaba911 said:
Thanks for the info, its help a BIT. :p
The real mystery is how to make the tuner to change frequency, I GUESS is I2C or other serial protocol is used to change, I tied to change the tuner supply voltage "+30v", it is working but very ruff. I collected more than 10 VCR for this project, any specific brand is better than the other tuner?
I think most of the tuner has the RF and IF on the same board.

It is not a stone age VCR's, 1-4 years old..

Anything else you can help, PLEASE...

STEVE

You need to find a tuner that you can get a datasheet for, I've had no luck at all finding one. One of the largest tuner manufacturers is Philips Components, but I've had no luck finding tuner data on their site.
 

pebe

Member
csaba911 said:
Ok
Now I have a bunch of useless VCR. :?

can some one send me a datasheet for this chips AN8560K and TD6359N

Thanks
STEVE
Do a search for TD6359N on Google. It will point you to the 'Chipdocs' site and you can do a free download from them.
 

pebe

Member
Sorry. It said 'download' and that's as far as I searched. I assumed it would be free.

If you know the manufacturer you can often get free downloads of data sheets from them.
 

csaba911

Member
I did send email to Toshiba, if they helpful as before, I guess never have the datasheet for this IC. :!:

I always search google before I ask for help.
Thanks anyway.

STEVE
 
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