The valley of the Kokcha leads directly from the Oxus to Faizabad, the capital of Badakshan, and its head is close above Ishkashim at the southern elbow of the great Oxus bend, a low pass of only 95 00 ft.
Notwithstanding these elevations, this portion of the state makes a distinct break in the continuity of the Northern and Southern Rockies, giving a broad, relatively low pass utilized by the Oregon Trail in early days, and by the Union Pacific railway at a later period.
Where the video signal is entirely encoded in digital form, the low-pass filtered step will not have the desired effect.
In addition, you can bypass the low-pass filter entirely, for a bandwidth of 20 kHz.