[ARC5] OK Smart People- FM Demodulator

[Ian Wilson]

Good morning David.

The 820uH inductor sees not only 100pF but also the 33pF coupling
capacitor in parallel. Add a few pF for strays and the input capacitance
of the mixer and you are down to about 470kHz, at least according to
the horrible calculator app that I am being forced to use at the moment.

73, ian K3IMW

On Fri, Jan 18, 2013 at 4:58 AM, David Stinson <arc5 at ix.netcom.com> wrote:

> Calling all "Smart People:"
>
> Doing some research on a "Borg Implant" FM Demodulator
> in the hopes of breathing life into many dust-gathering VHF sets.
>
> I found this interesting circuit:
>
> http://jaunty-electronics.com/**blog/2012/08/no-tune-ne602-**
> ne612-fm-demodulator/<http://jaunty-electronics.com/blog/2012/08/no-tune-ne602-ne612-fm-demodulator/>
>
> It's supposed to work between 420-500 KC.
> I'm hoping to "tweak" something like this for 15 MC,
> since the NE602 / NE612 will work well into UHF.
> What puzzles me is the tank circuit L1 / C5.
> 820 uH and 100 pF resonate at 555 KC.
> Is that right?  And if so, what resonant freq would
> one use to get the thing to work at 15 MC?
>
> 73 DE Dave AB5S
>
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