MMSSTV is a free Windows based software package which can receive and transmit SSTV and RTTY written by JE3HHT - Makoto Mori.
But, and it's a big but, it doesn't handle the original Copthorne McDonald standard. Even the 8-second B&W mode requires VIS codes. But it is useful for the spectra display, sadly that's about it for us. The website is here...
http://hamsoft.ca/pages/mmsstv.phpOlder DOS based software like JVFAX do handle the CM (Copthorne McDonald) standard but don't have the spectra display - it is a much simpler package, as you'd expect.
The plot you show is of the updated Robot 70 demodulator shown in the posting of 28/02/2015 (This thread, page 2). It's just of the filter after the differential amplifier. I modified this section of the demodulator to a) get the signal 'the right way up' by reversing the inputs to the differential amp. b) added VR101 to set the sync-tips to 0V, c) added VR102 to set the video level. The actual filter is unchanged. (Revised circuit diagram below).
The input to the filter is the junction of VR102 wiper and R120. If you want to make the filter unity gain, remove R121 (open circuit) and change R120 to 10K, the response is unchanged. You'll note - no inductors required.
R120/121 could be 22k with very little change in the response, but it would still have a gain of 0,5, -6db.
Steve A.