[BC] Freeland Rebuilds

[RichardBJohnson at comcast.net]

Ahaa the RCA BTF-20x, now that brings back memories. Early on that
rig was built with a plate-blocker that sat on a Rexolite shelf.
Rexolite is a cross linked polystyrene plastic,
 http://www.polymerplastics.com/mechanical_rex.shtml
that has great RF characteristics, but will burn like an acetylene
torch as soon as an arc path occurs. It sits in the hurricane
from the blower and, once started, molten aluminum will flow
all over the transmitter site, setting everything on fire
including the whole transmitter site. To "fix" this problem,
RCA had some RCA-Service Techs like me attend a special seminar
in Meadowlands, PA., to learn how to install a so-called "retrofit."
This was a meter with some adjustable set-points and some additional
control logic. Since the RF arc path was after the plate blocker,
once an arc started, the PA didn't overload. It just took the power
it had been sending to the antenna and burned it up in the PA box
–all 20 kW of it.

The retrofit was supposed to shut down the transmitter if an arc
occurred. It sometimes worked. However, a few weeks after I installed
the kit at WMMR (Metromedia) with its transmitter atop the PSFS
building in Philadelphia, the transmitter caught fire, burning out the
whole top floor of the building, including a lot of expensive AT&T
microwave equipment.

I was instantly fired. I must have done something wrong because,
after all, the smart engineers in Meadowlands could do no wrong.
This was another reason why, once I started designing radio transmitters,
I worked so hard to put companies like RCA out of the business.

Cheers,
Richard B. Johnson
Work: http://www.Route495Software.com/
Book: http://www.AbominableFirebug.com/

----- Original Message -----
From: "radioranger" <radioranger at comcast.net>

Are you really talking about an RCA BTF-20 FM transmitter doing 25 KW?  I
had always thought that the transmitter should be re-labelled the BTF-18.
You must be doing something incredibly right.

Steve Brown
Radio Rangers
Minneapolis,MN