lidnariq wrote:
I should remember to plug the RF output of my SNES into my oscilloscope and get a spectrum plot. It's no spectrum analyzer, but I bet even with crappy resolution I'll see a few interesting things.
Connecting my oscilloscope directly to the RF output of various things. No cart, so solid screen and no sound, scope set to 250MS/s and 50mV/div, the lowest setting that's not additionally bandwidth limited.
NES-001, channel 4:
Primary video carrier image at 67.25MHz; ≈-47dB during vsync/hsync/blanking and ≈-54dB during whatever color it randomly chose.
Audio carrier visible at 71.75MHz, ≈-65dB
Extra modulated signal visible at 62.25MHz, comparable in magnitude to the audio carrier.
Main 21.47MHz system clock visible; ≈ -65dB
NES-001, channel 3:
Primary video carrier image at 61.25MHz, ≈-45dB and ≈-53dB as above
Audio carrier visible at 65.65MHz (should be 65.75), ≈-61dB
Extra modulated signal visible at 66.65 ≈-68dB
Extra modulated signal visible at 56.70MHz, also ≈-61dB
Main 21.47MHz system clock visible; ≈ -65dB
SNS-001:
Weird ringing even when no power adapter plugged in at 66.75MHz, regardless of RF channel setting. ≈-64dB. Image disappears if via RF switch
and console is off.
SNS-001, channel 4:
Primary video carrier image at 67.25MHz, ≈-46dB
Audio carrier visible at 71.75MHz, ≈-64dB
Extra modulated signal visible at 62.8MHz, ≈-61dB
SNS-001, channel 3:
Primary video carrier image at 61.30MHz, ≈-44dB
Audio carrier visible at ≈65.80MHz, ≈-60dB
Extra modulated signal visible at 56.80MHz, ≈-59dB
Unfortunately, the SNR of my scope isn't good enough to see anything quieter, and the whole FM radio band is coupling into everything.