Topband: Some additional WLW comments

[Jay Adrick]

Some additional comments on WLW following on to Paul, Barry and Mark's
comments.

The RCA installation crew took the WLW rig up to 850 KW out during the
initial testing. The actual PA voltage was 12KVDC and the average load on
the power supply could go up to 100 amps...  1200KW in for 850KW out.  The
modulator was running Class B, so high distortion was typical as compared to
today's standards. Everything in the rig was basically overdesigned but
protection circuits were not always quick to react. With no automatic audio
gain control, it was quite common to blow components or pop breakers when
the modulation got out of control. The Crosley engineers later developed
some of the first audio limiting and AGC equipment to make the rig operate
more reliably.

There were only six transmitters at the other site, not thirteen. The six
200KW Crosley transmitters down the road were short wave (6 to 24MHz)  not
medium wave transmitters. They were set up in pairs with two RF decks and 1
modulator and power supply. In that configuration they were transmitting
diversity on two frequencies. The calls were WLWO, WLWK and WLWL. Crosley
built the station for the Office of War information which later became the
VOA. We operate the National VOA Broadcast Museum from the facility along
with the Gray History of Wireless collection and the Cincinnati Media
Heritage collection.

I have a longtime friend who was one of the design engineers for the VOA
site and is the last remaining engineer to have run the RCA 500 KW at WLW.
We often joke with Clyde as why he never took up ham radio as a hobby. His
response is "once you have dipped the plate on a rig at 100 Amps at 12 KV,
noting else can excite you".

I enjoyed the comments on the 2000KW middle east transmitters. They were
built by Harris Broadcast and are solid state. We put similar TX's in the
Voice of Vietnam and in the Philippines. My youngest daughter who teaches
physics got to visit the transmitters when we had them on the test pad out
in Quincy, Il. She was asked to push the big red button that brought the rig
from a cold start to 2000KW in about 10 seconds. At 100% modulation (8,000KW
PEP) we were melting snow and scorching the grass outside behind the dummy
load!

Each year on Friday evening during Dayton, Geoff W8GNM, Ted Ryan W8SAI and I
host an open house that alternates between the VOA site and the WLW
transmitter site. If any of the readers are interested in attending, please
contact me before Dayton. We try to limit the size of the expedition to
about 40 attendees.

73 Jay K8CJY 

jadrick at cinci.rr.com