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January 29th 05, 07:25 PM

On 29 Jan 2005 01:51:32 -0800, wrote:

'Scuse the silly nit-picking here

Ah!! Something that I can join in with....

but those unlicensed old open-cabinet
induction heat-sealing machines operated around 27 Mhz back when
licensed hams also operated on those freqs. If I recall it right
problem was that 11M was a shared band and us licensed types had no
legal bitch on heat-sealing machine RFI, it was live with it or go play
on some other ham band.

But eventually the FCC lowered the boom on the heat-sealing machines.

The major problem with the old-style heat sealers was the harmonics
which were generated - the fundamental frequency swept upwards as
the plasitic melted and the fifth harmonics fell in the aviation band.

Upon complaint from the FAA backed up by FCC field measurments, the
local FCC Engineer in Charge (now called District Director) has the
legal authority to issue a Cease and Desist Order closing down not
only the machine in question but the entire site until the site was
certified harmonic-free and so verified by an overflight of the
FAA's (notorious) instrumentation plane, usually piloted by a
someone we called - with sufficient reason - "Vertical John". We
always declined to accompany him....

We didn't like to use that authority too often because it would result
in the unemployment of a lot of minimum-wage immigrant employees.

Then they tossed us out of the band and turned it over to the CBers.
Which at the time was (temporarily) another licensed service. Ah, the
webs "they" weave . . !

In reality, it came about when the ITU designated the band 27.12 +/-
160 kHz for "Industrial, Scientific, and Medical" and in came the
heat sealers, diathermy machines, and similar noise generators. That
resulted in 11 meters being turned into an electronic garbage can.
The CBers got it on the basis of "if you can use it for any local
communications through all the garbage, go ahead and do it".

The only reason that any communications can be conducted on that
band now is that all the shielding, bypassing, and grounding
necessary to comply with the harmonic elimination requirement also
keeps the fundamental from being radiated.

A ham for whom I was the "elmer" some 30+ years ago became the test
engineer at the Varian Tube division that manufactures the
wastebasket-sized tubes for ultra high power uses, and Ray swore
that someday he was going to design a test jig that would have all
the harmonic suppression but permit the unlimited field radiation
allowed for ISM devices on 27.12 MHz, thereby solving the "CB
problem" for about one-third of the US.

He never did.....

--
73 de K2ASP - Phil Kane

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