[Milsurplus] dynamotor relics

[Richard Brunner]

A bit more about dynamotors, etc:
The typical ac power supply has an LC filter, which "rings" upon a step
load change when you hit the key, causing an interesting damped
oscillation on the leading edge of your signal.  I have not observed
that with dynamotors, or had no reason to look.  Also voltage drop in
dynamotors occurs over several seconds as it slows under load, won't be
noticeable in use, and is small anyway.  I am also partial to regulated
supplies, but do give dynamotors a chance.

A word about the 800-1 inverter being "over the top."  The noise is
mostly from magnetostriction at 1600 cycles from the iron, and I
measured 95 dB at three feet, which is the same as a subway train
running through the shack. (Headphones won't help much.)  Upon advice
from a local noise abatement expert, I constructed a box of 3/4 inch
plywood, with joints glued and screwed, (no gaps!) lined with 2 inch
thick fiberglass batts.  Also two chimneys two feet long, folded
underneath, also lined with fiberglass batts, to move air in and out.
This reduced the noise to about 50 dB, which is the same as normal
conversation.  Depending on where you stand you may hear nothing, or a
distant whine.  I find this very satisfactory, and less noisy than some
ac supplies.  I suspect we would complain more about noise from ac
supplies, but we don't hear good at 60 or 120 cycles.

Richard, AA1P