I recently finished reading a book about one of the
biggest medical fraudsters in US history who snake-oiled his way
to riches during the 1930's in the United States and then from a
powerful AM radio station on the Mexican border. His name was
John R. Brinkley and he called himself a physician though he had
no valid medical degree.

	Most of the book is not directly radio-related, but
there is a brief description of Brinkley's Mexican boarder radio
station which later became XERF and I am sure some of you
remember the preachers selling all kinds of stuff that one could
hear after dark on XERF.

	XERF's transmitters were just across the river from Del
Rio, Texas and, at one time, were 500,000 Watts directional in
to the United States.

	People report that at night, the antenna towers arced
with green flashes. XERF leaked in to telephones in town, could
be heard on things that weren't even electronic such as bed
springs, and made the headlights of cars come on even when they
were supposed to be off as they drove around town.

	XERF transmitted on 735 KHZ in the mid thirties and many
of the radios were TRF or Tuned Radio Frequency receivers. These
were the predecessors of the superheterodyne radios we are more
familiar with. In a TRF radio, you have 1 or more tuned circuits
which you peak and tweak until they are centered on the
frequency of the radio station you want to listen to. There is
no IF, no conversion, no nothing; just tuned tank circuits of
sometimes dubious Q factor between the antenna and detector.

	If you ever had a crystal radio or have seen an old
radio from the early part of the last century, it was a TRF.

	In the 1930's, XERF had such a power-house signal at
night that people trying to listen to other radio stations in
other parts of the AM band suffered interference from Brinkley's
transmitter no matter where they tried to tune.

	It was a combination of tremendous AM transmitter power
coupled with basically poor quality receivers.