[sdiy] [OT reply] oscilloscope considerations

[Scott Evans, Gen Mgr]

Bob,

You are correct for signals before/after demodulation. However, "IF"
video carrier frequencies for CATV (cable) are 38.9 MHz or 45.75 MHz,
depending on the standard. IF demodulation for monitoring signals
requires instruments in this range, i.e. for bandpass tuning. One would
need a good 100Mhz scope, IMO.

Suppose this is my fault for using "Video" instead of being more
specific. Seems I just get online to late at night.

Regards,

Scott

Bob Roesler wrote:
> 
> The highest frequency in american (NTSC) composite analog video is 3.58
> (actually 3.579545 as I recall) Mhz. It is the subcarrier used to encode
> decode chrominance information. Composite digital video has a pixel rate of
> 4xsubcarrier (14.31818Mhz). The (relatively) industry standard (CCIR601)
> component digital video is roughly the same rate, though it's not based on
> subcarrier frequency, but rather a standard fixed clock rate that could be
> shared amongst the NTSC & PAL world. Seems like 200Mhz, though plenty fine,
> might be a little more than one would need for most video. At least this
> goes for video for standard definition television.
> 
> my2bits
> 
> Bob
>