Panda

[JimB]

I suggest that this is not an easy task.
To try and get an idea of the amount of radiation from the local oscillator in the tuner, I connected my spectrum analyser to the antenna socket of a TV set. Actually I tried two TVs with different results.

The first TV, I could not see the fundamental frequency of the local oscillator at all, but I could see the second harmonic at -74dbm and the third harmonic at -66dbm. The level varied considerably depending on which channel the TV was tuned to.

The second TV, I could see the fundamental of the local oscillator at about -66dbm. Again the level varied considerably depending on the channel.

For the decibel challenged, -66dbm is equivalent to about 0.11mV in a 50 ohm system.

So if you can find a frequency counter which will reliably count 0.1mV signals at UHF in the presence of who knows what else, and that is directly connected to the antenna socket so there will be all the off air signals, you have got the problem cracked.

JimB

 

[Diver300]

I think that there is a far simpler way of doing this.

Just build a receiver for the remote control. Record the key presses on the remote control with your receiver, which obviously should be close to the TV.

The remote control signals are well known and it's easy to find how they are encoded.

Most importantly, you are working with signals that are designed to be received by the cheap IR receiver in the TV, so you just need a similar receiver.

 

[mbarazeen]

Diver300,
as on your 1st suggestion he needs it to work when the TV is connected to on air signals, so antenna terminal wont be free, your 2nd one can work with IR receiver, but two problem he may face
1) encording and other processing a similar task as discussed for other ideas
2) it cant be used as a common device for many TV sets, so that it will require similar channel information as tuned on the TV fed to this IR receiver.

he can work on the one that is more suitable.

razeen

 

[Dharshana]

Razeen,

I found a "Portable Digital Frequency Counter 50MHz-2.4GHz LCD Displayer" when searching the ebay.. It costs US $ .......
Will this capture TV frquencies (UHF/VHF) ?? Also does it change values when changing the TV channel ???

 

[mbarazeen]

it will count the frequencies in the range mentioned, but it should be only one signal at a time also the level of the signal should be enough for it to read. this case you will have to directly connect it inside the TV set to its local oscilator output, that is inside the tuning module, without loading it. also check on the specification of the counter about the minimum input level.

for your project i beleive you need some other device too, to process compare and log the information. better discuss with one of your doctor in this field he can direct you to the correct path.

razeen

 

[3v0]

Will monitoring the TV frequency work if the person has cable or satellite TV ?

I think you task is more easily solved using a box that knows how to decode the small number of remote formats. You will need a uC to record data anyway.

 

[Nigel Goodwin]

This seems a completely pointless thread?, there's already a VERY long established technique for doing this, certainly in the UK - for recording TV viewing statistics (where do you think the viewing figures come from?).

Over the years I've seen various 'boxes' for doing this, both on customers sets and rental ones. Essentially an engineer is sent out, who hardwires a box directly to the local oscillator inside the tuner, this connects to an external box which records all the required information, and transmits it via modem over the phone.

Same applies to VCR, cable and satelite boxes - accurate information is gathered from them, and transmitted via modem.

A further VERY important part is filling the forms in, the viewers need to fill in who was watching, and their age groups and sex, in order to give accurate information.

Households are selected at random, and I actually received an offer the other year, but turned it down, I couldn't be bothered with all the form filling.

As for externally detecting the channel, TV detector vans in the UK routinely did this for years, from out in the street - although there were only ever a VERY small number of them, and I don't know if any exist today or not?. Basically you had a VERY skilled operative with expensive communications receivers fed from a directional aerial. With this they could pinpoint which room a TV was in, what channel it was tuned to, and even if it was colour.

I've been in one once, it was very impressive what he could do with it.

 

[Hero999]

Just because someone's got their TV turned on, it doesn't mean they're actually watching it so monitoring TVs will give inaccurate data.

 

[Nigel Goodwin]

Just because someone's got their TV turned on, it doesn't mean they're actually watching it so monitoring TVs will give inaccurate data.

That's why the viewers have all the forms to fill in as well.

 

[Dharshana]

Any Idea to get frequencis from "IF Out" of the TV tuner set... I have little knowledge of TVs....

 

[Nigel Goodwin]

Any Idea to get frequencis from "IF Out" of the TV tuner set... I have little knowledge of TVs....

No, because it's always the same - that's what an IF is.

You tap inside the tuner, on the LO.

 

[Dharshana]

Is that so ....

What do you mean by LO........
Could you pls tell me how to tap inside the tuner.. PLS HELP ??

 

[Dharshana]

I'v attached below TV tuner diagrams. Does anyone know how to get the tuned frq. from the tuner to a displayer

 

[Nigel Goodwin]

Is that so ....

What do you mean by LO........
Could you pls tell me how to tap inside the tuner.. PLS HELP ??

LO is Local Oscillator

 

[Nigel Goodwin]

LO is Local Oscillator

As that has at least two oscillators (UHF and VHF) you would need to tap off both, but there's no circuit of it in your post.

Is that the EXACT tuner you're using?, because every one will be different, and most modern tuners will already have internal 'taps' for the PLL tuning.

 

[Dharshana]

It is similar of that...
Pls give me steps for doing this

 

[Nigel Goodwin]

It is similar of that...
Pls give me steps for doing this

I've no idea what you would need, I've never done it - I've only ever seen the modified tuners in sets where it's been done to collect viewing statistics.

 

[blueroomelectronics]

As suggested by a previous post an IR detector & microcontroller would be my suggestion too.

 

[tcmtech]

Did I mess something in the post as to what you are planing to do with this if it works?
What purpose or reason do you feel you need to be able to collect such information on or from TV sets for?
Just curious.

 

[blueroomelectronics]

It's probably a school project.