[sdiy] filter response on a scope

[David G. Dixon]

Hey Team,

Lastnight I designed a board to extract 18 additional filter responses from
my 2164 4P LPF, thus bringing the total number of filter responses from the
module to 22 (4 LP, 4 HP, 6 BP, 2 N, 4 AP, and 2 more as yet unspecified).
It will involve a 1U panel with 18 jacks on it sitting next to the 3U filter
panel (hence my last query about PCB mounting), or it could just be a 4U
panel.

I'd like to be able to look at the filter responses on my old Tektronix
scope, but I'm not sure how.  I'm thinking a sawtooth sweep of expo FM on a
sine-generating VCO into the filter at constant cutoff, and then perhaps
taking the filter output through an envelope follower and then into the
scope to see just the positive outline of the response.  However, if anyone
has a nice method for doing this, I'd love to hear it.