[sdiy] Making an audio spectrum analyzer from an old Casio LCD TV

[aankrom]

 What I was thinking about would involve using certain guts of old TV's 
 or VCR's. I like the idea of using re-used parts. I have an old article 
 that shows how to make a spectrum analyzer for RF frequencies using a 
 heterodyne method that uses an oscilloscope. I may just modify that 
 design.

 AA

 On Fri, 09 Sep 2011 10:45:46 -0700, Eric Brombaugh 
 <ebrombaugh1 at cox.net> wrote:
> On 09/08/2011 08:42 PM, aankrom wrote:
>> I have an old hand-held Casio LCD TV and I thout it would be cool to
>> make an add-on for it that would allow it to function like a 
>> spectrum
>> analyzer. I was going to start with some sort of heterodyne system 
>> for
>> the fron't end, but getting the final output to NTSC video is the
>> insurmountable hurtle. It can be monochrome so I don't have to mess 
>> with
>> color. I've seen projects using microcontrollers that output VGA, 
>> but I
>> like my little TV idea.
>>
>> If I'm not mistaken would the easiest way to do it be to have the TV 
>> on
>> it's side?
>>
>> Anyone done anything like this?
>
> There are a couple of ways to do something like this, but basically
> it boils down to handling it digitally or in analog hybrid. I think
> the OP is referring to the latter.
>
> In the analog hybrid approach, you'd have a video line counter that
> controls a sweep oscillator tuning across some band of interest. At
> each video line you'd dwell, integrating the energy at that frequency
> and using the result to control the 'on' time of the video line. This
> would result in a spectrum analyzer with the vertical axis being
> frequency and the horizontal axis being magnitude/power. It's a 
> fairly
> simple concept that could be done with a low-end MCU coupled with
> oscillators, integrators, etc.
>
> The digital approach would use DSP (FFTs, windows, etc) and more
> conventional video generation systems to create a frequency display 
> in
> any format. I've done something like this with a dsPIC and a low-res
> graphic LCD here:
>
> http://members.cox.net/ebrombaugh1/synth/dsPIC_lcd/index.html
>
> Probably not what the OP was talking about though...
>
> Eric
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