In article , Roy Lewallen says...

The only variable delay lines I've ever seen with the delay variable
more than a couple of nanoseconds are some units used in an old
Tektronix instrument of some sort. They're awfully rare.

Oh, they exist. They're often used in simulcast radio systems at
each transmitter site. The idea, of course, is to insert a calculated
delay into the modulation so that the audio signals from each site don't
end up phase-cancelling one another.

Allen Avionics is a big maker of variable delay lines. You may
want to check Ebay for them.


--
Dr. Anton Squeegee, Director, Dutch Surrealist Plumbing Institute
(Known to some as Bruce Lane, KC7GR)
kyrrin a/t bluefeathertech d-o=t c&o&m
"Quando Omni Flunkus Moritati" (Red Green)