Batboard

if i want to record 17 frequencies from my local simulcast @ 12.5 kHz bandwidth of raw P25 data with a SDR radio what would the Mb/s requirements be at max all 17 in use????

Depends on how wide a snapshot of spectrum you want to take.

Are you going to record 17 channels individually, or sample a huge slice of spectrum containing all those channels? If so, how far apart are the lowest and highest frequencies?

The width of the signals together in one chunk, mixed down to baseband like you'd see on a spectrum analyzer. If you want 453.000 to 453.500, you're going to need 500KHz of baseband, and the sample depth is your dynamic range.

(17 * 12.5KHz) + (17* guardbandwidth) = $number
$number * sample depth in bits = $samplebitrate