A recent thread showed a low res Spectrum Analyser.
I have just done a bit of twiddling and found that you can make a 'rough' Spectrum Analyser using the Nat Semi LMF100:-
http://uk.farnell.com/9487735/semiconductors-integrated-circuits/product.us0?sku=national-semiconductor-lmf100ccn
Unfortunately I did it using a PIC, so I cannot post any PICAXE code.
Suffice it to say all you do is use PWM to control the LMF100 switching speed.
The chip provides control of bandwidth and has a Bandpass output which you can rectify and read using ADC.
No, its not as good as FFT by a long way, but you can't FFT on a PICAXE. Well maybe you could but the calcs would take all day.
By setting PWM then READAdc in steps you can get numbers showing the amplitude in that F-band (not forgetting bandwidth), so it's a bit rough but gives reasonable results as long as you don't expect high resolution.
You may need an aliasing filter depending on your source - all in the Data Sheet if you can be bothered to read it
The same chip can also allow you to make a PICAXE controlled low-pass and band-pass filter which may be of interest to users of mushy radio reception.
I have just done a bit of twiddling and found that you can make a 'rough' Spectrum Analyser using the Nat Semi LMF100:-
http://uk.farnell.com/9487735/semiconductors-integrated-circuits/product.us0?sku=national-semiconductor-lmf100ccn
Unfortunately I did it using a PIC, so I cannot post any PICAXE code.
Suffice it to say all you do is use PWM to control the LMF100 switching speed.
The chip provides control of bandwidth and has a Bandpass output which you can rectify and read using ADC.
No, its not as good as FFT by a long way, but you can't FFT on a PICAXE. Well maybe you could but the calcs would take all day.
By setting PWM then READAdc in steps you can get numbers showing the amplitude in that F-band (not forgetting bandwidth), so it's a bit rough but gives reasonable results as long as you don't expect high resolution.
You may need an aliasing filter depending on your source - all in the Data Sheet if you can be bothered to read it
The same chip can also allow you to make a PICAXE controlled low-pass and band-pass filter which may be of interest to users of mushy radio reception.