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Dr. Barry L. Ornitz[_3_] · April 2nd 09, 11:31 PM posted to rec.radio.shortwave

"~ RHF" wrote in message news:bfa72
...
On Apr 2, 2:38 am, msg wrote:
When I was a kid, our nearby hospital spit out lots of RFI from
diathermy equipment,and there was a quite predictable schedule
for the QRM on several bands, but I don't remember the
frequencies any more - safe to say that it was strong on
fundamentals and harmonics over much of 80 through 10 meters.

Circa 1960s - Used to get a beautiful scrolling pattern on one of
the Lower VHF TV Channels when the local Hospital {three blocks
away} was running one piece of their Medical Equipment.

Industrial, Scientific and Medical equipment is governed in the USA
by the Federal Communications Commission under the Code of Federal
Regulations, Title 47, Part 18. There are only three ISM bands
falling in the shortwave spectrum although a fourth is just above
the normal HF spectrum (47CFR,Part 18,Subpart C,§301). The
frequencies a

Frequency Tolerance
6.78 MHz ± 15.0 kHz
13.56 MHz ± 7.0 kHz
27.12 MHz ± 163.0 kHz
40.68 MHz ± 20.0 kHz

When operating on an ISM frequency, the emission standards for
unintentional radiation are considerably relaxed from those on other
frequencies. Thus it is frequent that SWL's hear signals on the ISM
bands. And for those considering pirate radio broadcasting on ISM
frequencies, the ISM rules prohibit the use of ISM frequencies
for communications. Unlicensed communication devices operating
within the shared ISM bands are governed by Part 15, Subpart B of
the FCC rules and regulations.

In one of my previous jobs, I was responsible for compliance testing
of several RF heaters. All but one operated on ISM bands; the one
that didn't required considerable care to keep it within emission
limits. It operated in the vicinity of 100 MHz at a power level of
15 kilowatts.

73, Dr. Barry L. Ornitz WA4VZQ