Mike Knudsen ) writes:
In article , --exray-- writes:
I once had an Ameco VFO (VFO-621?) that had a simple little varicap
modulator circuit built in. It sounded great. I bet you could find
such mods in some of the older magazines.
Long ago, like early '70s, Popular Electronics mag had a short article on how
to FM a 6m rig with a varicap diode across the oscillator tank. Very short
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 would
be less messy on TV picture or sound than an AM signal. SSB was blissfully
rare on VHF back then. --Mike K.
They were certainly running such articles in the early sixties, if not
earlier. FM was promoted from time to time as an antidote to interference
since at least it wasn't something that would be demodulated. If strong
enough, it would bias something wrong, but the modulation would not be
But that early, the assumption was that the ham at the other end would
be using an AM receiver, and would slope-detect the FM signal.
As someone pointed out, there were a number of commercial VFOs
in the sixties that had a jack for a microphone so you could FM it.
You'd feed it into the matching Communicator.
By the late sixties or early seventies, of course, the point shifted
so people wanted to FM their VFOs in order to get in on that newfangled
FM and repeater thing. There were various articles about converting
those old Communicators and Cleggs to FM, but this time around, not
only would they add FM to the transmitter through various schemes,
but they'd throw in an actual FM detector.