On Thu, 2012-08-16 at 09:39 -0700, Harold Hallikainen wrote:
> I don't have datasheets on those specific parts, and they may be OEM part
> numbers. The ceramic filters I used were from Murata. You might check the=
m
> out.

I don't believe so, it seems to be some sort of industry standard
marking since I've seen many other boards with similar filters marked
similarly.

> A "ceramic discriminator" is just a ceramic resonator that is used in a
> discriminator (FM demodulator). It replaces a parallel LC filter used in =
a
> quadrature detector FM demodulator. As I recall, the IF is applied to the
> filter (whether ceramic or LC). As the frequency varies (as in FM), the
> phase between the voltage and current varies. This phase difference is
> used to determine the instantaneous frequency and demodulate it.

I'm sorry, but this is way over my head, do you have a pointer to
something that describes this sort of stuff from a more fundamental
point of view?

> So, good luck with your filters! The band pass and notch filters probably
> have an input, an output, and a ground terminal. They need to be driven
> and loaded with a specified resistance for them to work properly. The
> discriminator is probably a two terminal device that is designed to work
> with a specific chip (like the SA639 I mentioned before).

Ahh, see, as mentioned in my post, the 3 devices are 3 pin, so I don't
think it is a discriminator?

I've looked at another board I have. It contains a TDA9800 VIF-PLL
demodulator and FM-PLL detector chip.

I've traced the filters involved (they again look very similar to the
link) and referencing the typical circuit in the datasheet, it looks
like the one labeled T4.5C is a sound trap (so notch filter to rid the
4.5MHz sound carrier from the video side) and the other is labelled
F4.5E, labelled sound filter, so I assume that means it's a pass filter.

Still would love if someone could confirm/deny my suppositions here! :)

Thanks, TTYL

--=20
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