From obxwindsurf@yahoo.com Fri Oct 03 02:55:09 2003
Subject:Re: Solid State scanner project - warning: very geeky discussion follows!

Nope. The scanner is a rotary switch that rather than use contacts
is a rotating air capacitor (similar to an old radio tuner)
consisting of 15 sets of fixed plates with air gaps between each
plate in a set, and a rotor with a set of plates which interleave
with each plate in a fixed plate set. To each set of fixed plate is
the V/C switch and to the other side of the V/C switch are connected
the various taps of the delay line. The delay line is a serially
connected set of LC networks (2nd order low-pass filters), which
exhibit phase shift with each stage. As the scanner rotates, its
output picks off and blends the signal from one stage with that of
the next one that the V/C switch selects. The connections to the
rotor are such that half of its rotation runs up the delay line
taps connected by the switch, and the remainder of the rotation
scans back down.

Our discussion was centering around the transfer function of signal
as the rotor swings between two adjacent sets of fixed plates.

It's not like a BBD or anything like that - a BBD in any
configuration has not successfully produced the sound because of the
characteristics of the line itself and how it is scanned.

If you do a search on Google for Hammond vibrato line box scanner,
you'll find a wealth of information including pictures of how it
works.

Hope this helps,
Kevin

> seen a scanner but what are your thoughts ?
>
> Best regards,
> Claire
> Australia