administrator wrote:
Let me ask you a question: would you be able to tell wheter a TV is switched on using a spectrum analyser? (the analyser would be in the same room right next to the TV). I am asking becasue I am interested in finding out whether you can spot the intermediate oscillator frequency of the TV.
It depends. Are you asking about the IF (post mixing), or the LO used to mix the input with.
If one was to connect the antenna socket of the TV to the input of the spectrum analyser with a cable, then possibly.
No filter is perfect, and some leakage of the IF may be possible. I have seen the IF from other (non TV) receivers on an analyser this way.
Leakage of the LO is probably more likely than leakage of the IF.
This all assumes classic superhet type rcvr with an analog IF.
What is more interesting is the possibility of direct conversion digital receivers. I'm not sure if any are being commercially produced yet, but they (in theory) would have the possibility of not leaking. Some of the USB 'key fob' TV receivers look interesting, as they seem too small to hold the usual shielded analog mixing design.
I'd expect an 'all digital' receiver to look something like:
antenna -> SAW filter -> DSP -> digital output.
There being no real LO as such, just the DSP doing the mixing stage in software.