[sdiy] Black Magic oscillator cans

[Tim Ressel]

--- Magnus Danielson <cfmd at swipnet.se> wrote:
> From: Tim Ressel <madhun2001 at yahoo.com>
> Subject: Re: [sdiy] Black Magic oscillator cans
> Date: Sun, 20 Jul 2003 16:32:33 -0700 (PDT)
> 
> > Hey all,
> > 
> > Thanks for all the responses. What a group! Now
> that I
> > think about it, It's kinda hard to tune a crystal
> so
> > your gear is in tune with someone else's. Maybe
> its
> > time for an adjustable oscillator. Someone
> mentioned
> > an LC oscillator. I think I have an adjustable cap
> > somewhere.
> > 
> > Thanks all!
> 
> I think you should be able to make do by using a
> 4046 and a pair of dividers.
> 
> The 4046 (or at least any of its 74HC/HCT variants
> (4046, 7046 and 9046) is
> able to spit out the 2.00024 MHz you want. Now, you
> need two dividers to do
> the reference-frequency. If you take a 11 MHz
> crystal oscillator, divide it by
> 12500 and then have the output of the 4046 divided
> by 2273 and then toss these
> into the phase-detector of the 4046. The loop-filter
> should be a wide-bandwidth
> filter, but recall that the reference frequency is
> just 880 Hz.
> If you have a CPLD or FPGA in the neightborhood,
> then the frequency divider
> stuff is quickly done. If you do them in CMOS you
> might need to do some
> fiddling.
> 
> However, if you have a TOG on the output of this
> 4046 anyway, I suspect
> greatly that you get the 880 Hz output anyway, so
> that divider-chain is for
> free. And the 12500 is 5 * 5 * 5 * 10 * 10 so you
> should be able to use several
> small dividers of your choice in many different
> combinations.
> 
> Another method is to build a LC-based oscillator
> with a varicap diode. However,
> the same booring divider-setup is needed for the PLL
> if you intend to hit the
> same frequency.... LC-based oscillators isn't bad
> when you put them under
> frequency/phase-locking.
> 
> Cheers,
> Magnus


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