[Milsurplus] [Boatanchors] FMing Prog. Oscillators (was GE Portamobil)

[Michael Clarson]

Dave: Perhaps this will help. Phase modulation looks easier than 2
oscillators. http://www.scomcontrollers.com/downloads/lcphasemod.pdf

Not sure if you can get at any of the circuitry in the programmable
oscillator, but a varicap across the crystal should give you nice FM.  Good
luck. --Mike, WV2ZOW

On Tue, Feb 26, 2019 at 10:30 AM Glen Zook via Boatanchors <
boatanchors at mailman.qth.net> wrote:

> You can always phase modulate the signal.  Remember, most of the old
> tube-type "FM" units sold by Motorola, General Electric, etc., were
> actually phase modulated (PM) instead of being frequency modulated (FM).
> Using PM would probably be easier to accomplish than other systems trying
> to FM the signal.
>  Glen, K9STH
> Website: http://k9sth.net
>
>       From: David Stinson <arc5 at ix.netcom.com>
>  To: mrca at mailman.qth.net; boatanchors at mailman.qth.net;
> milsurplus at mailman.qth.net
>  Sent: Tuesday, February 26, 2019 8:15 AM
>  Subject: [Boatanchors] FMing Prog. Oscillators (was GE Portamobil)
>
> (Copied to other lists for general interest:)
>
> I've been working on a concept.
>
> Can't FM a programmable oscillator, but:
> Say you have a rig that requires Fo/18 crystal.
> So 146.52 would be 8140 KC.
> And you have another crystal laying around, doesn't
> matter the freq since we can order any freq prog. osc,
> as long as the crystal's a fundamental.
> Assume a common Color Burst crystal of 3.5795 Mc.
>
> We order a 4560.5 KC oscillator.
> With two transistors and a couple of diodes,
> we can sample mic audio through an adjustable
> audio amplifier, then apply it to an oscillator
> with the 3579.5 crystal, say in the Emitter lead.
> This crystal oscillator WILL FM at the audio rate.
> Output this and the prog. oscillator to a couple
> of diodes as a non-linear mixer.
> One of the products will
> be 8140 KC, FMing at the audio rate.
> Don't need much of the mic audio since we'd
> only need to swing the Color crystal about 300
> cycles, since it will be multiplied by 18.
>
>
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