First, thanks to Paul W9AC and John K5PRO for their accounts. I
worked at a FM near Memphis about the same time that was also a 3 KW
with 3 rototillers at 300 feet fed with pressurized heliax. That must
have been a standard configuration FCC licensed for small markets. I
don't remember the tube but our rig was a Harris and someone had
placed a box fan laying flat on top of the cabinet and I was told the
idea was to help pull air up out of the rig.
New blowers have gotten expensive, what a surprise, and I've managed
to get by so far with some hamfest finds. I think there are some
cheap ones sold on-line from China but as with tubes, I don't know
about the quality. But I wouldn't be surprised if Daytons are no
longer made in Dayton, hi. I am using a large blower removed from a
Sparta 701 AM broadcast rig that was wound to run on 230 v. but I've
put 120 across it which slows it down and quiets it. One set of
bearings is shot because it only runs smoothly when resting on its
side with the motor facing up. It's big enough so that on 120 v. it
still pushes plenty of air for a single 4-1000 using the black plastic
socket. It rests on an upside down plastic paint bucket with the
bottom cut out and holes cut in the side of the bucket so air comes in
and up through the wheel and out. Like the other fellow, who remoted
his blower, I am using flexible vinyl dryer duct to the rig. The
blower outlet is a square flange. I went to a hardware store and
purchased aluminum gutter sections that have the drain collar that a
downspout can push on to. I cut out the collar with enough gutter
aluminum sheet to make a square around the collar, and punched bolt
holes in the corners that lined up with the bolt holes on the blower
flange. Using silicone sealant I bolted the collar onto the flange,
giving me something to jam the dryer duct over and fasten with a hose
clamp. I used the same method on the RF PA chassis also.
73
Rob
K5UJ
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