TV Oscilloscope demonstrates FM modulator for sound carrier (updated)
Perry
Posts: 253
Heres a little project for sigma/delta ADC users
TV Oscilloscope with sound on VHF channel 2-6
modified sigma delta A/D Converter to modulate audio
at the correct 4.5Mhz offset from the video channel
few replies to this post but I updated it anyway
perhaps that other thread is scaring people off from trying this
I think the first schematic published by Parallax has caused many to avoid this circuit
if you use the suggested 10uf capacitor and 1Meg ohm resistor
it takes nearly 10 seconds to charge the capacitor, many people would turn off the "prop" before this
for fear of seeing smoke !!!!
Perry
Post Edited (Perry) : 10/30/2007 3:45:27 AM GMT
TV Oscilloscope with sound on VHF channel 2-6
modified sigma delta A/D Converter to modulate audio
at the correct 4.5Mhz offset from the video channel
few replies to this post but I updated it anyway
perhaps that other thread is scaring people off from trying this
I think the first schematic published by Parallax has caused many to avoid this circuit
if you use the suggested 10uf capacitor and 1Meg ohm resistor
it takes nearly 10 seconds to charge the capacitor, many people would turn off the "prop" before this
for fear of seeing smoke !!!!
Perry
Post Edited (Perry) : 10/30/2007 3:45:27 AM GMT
Comments
This looks very interesting. Can you say something more about what it does? What is the audio for (on an oscilloscope)?
this program does the sound carrier on the TV channel, something I have seen people ask for
but few demonstrations to show that working.
the vocal tract code does a good job of this though
http://forums.parallax.com/forums/default.aspx?f=25&p=1&m=152683
also after reviewing the code myself I see it needs a lot more work to be a useful 'scope
even though the ADC appears to work up to 1.25 MHz the spin part is too slow to pick up the data.
I will be looking into fixing that, now that I seem to have a bit of a handle on the propeller assembly code.
There is an other thread that asked about detecting low voltage transitions,
I now have some ideas about making the scope part more useful with triggering and horizontal scaleing
Post Edited (Perry) : 10/24/2007 7:11:01 PM GMT