You're talking about two different problems. Many of the early TV sets had
an IF frequency near 21 MHz. This was fine until hams were allowed to use
the 15m band in 1952. The 15m ham signals got into the TV IF section due to
inadequate filtering and/or shielding. This was the fault of the TV design
and not the ham operators although it caused much grief and aggravation to
the hams.
Also, back in those days, ham transmitters used class C biased final amplifiers.
These were prolific generators of harmonics. If the ham transmitter was not
properly filtered and shielded and used a low pass filter on the output, these
harmonics could cause TVI if they fell on a local channel. This WAS the fault
of the ham's equipment.
Two completely separate issues.
73, Roger
On 7/7/2018 7:44 PM, Ed K0iL wrote:
Remember the old days when the old TV sets had no filtering and the ham
causing the interference had to cease operations during prime time TV hours
until the problem was resolved? Ever wonder why the FCC didn't force all
TVs to be properly filtered to not be susceptible to out-of-band RF signals?
Simple. It's money.
The cost to properly redesign and filtering all the TV sets would've cost
much more than adding individual high-pass filters only where needed making
that a much lower costs because not every TV set sits next to a ham station.
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