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Old September 19th 03, 05:24 AM
William Warren
Posts: n/a

"Mike Knudsen" wrote in message

Long ago, like early '70s, Popular Electronics mag had a short article on

to FM a 6m rig with a varicap diode across the oscillator tank. Very

parts list, and the most expensive item was probably the phone jack for

the mic

BTW, this article suggested FM as a way to reduce TVI -- not clear why it

be less messy on TV picture or sound than an AM signal. SSB was

rare on VHF back then. --Mike K.

I never understood it, but it seemed to work: those who tried FM reported
that TVI *was* reduced. Since TV audio is FM, albeit at 25 KHz deviation, I
would have thought it'd be *easier* to cause interference by using FM.

Of course, perhaps it was a "second order" effect: perhaps it prevented
*audible* interference, and therefore prevented anyone from identifying the
source. I'd think that previous complainents might simply assume that the
local ham whom they'd heard on their TV before was causing the picture to
roll, but then again, I remember assuring neighbors that "If it was me,
you'd hear me talking", so I might be wrong there ;-J.

If anyone out there has the authoritative answer, please pass it along: did
FM cause less interference, or did it simply prevent the interference from
being in the audio chain?

Enquiring minds want to know!

(Remove ".nouce" for direct replies.)