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March 13th 04, 05:24 AM

In article ,
(Avery Fineman) writes, adding to a previous post:

In article , "Tam/WB2TT"
writes:

I don't know what you mean by ordinary crystal, but even.001% is not very
good. You may want to look at high accuracy temperature compensated
oscillators. Depending on where you live, you may actually be able to phase
lock your oscillator to the WWB carrier. You would have to use a phase
detector that does not pull you off to one side if you lose the signal.
Also, the ~3.58MHz color subcarrier on some TV stations is locked to a
cesium standard.

In the NTSC TV standards, the color sub-carrier reference frequency
of 3.579454545454545... MHz is related to the 5 MHz NIST standard
frequency by: (88 x Cs) / 63 = 5 MHz, were Cs is the sub-carrier f.
Integer dividers and multipliers can create one from the other.

The NTSC aural carrier frequency offset is exactly 4.5 MHz and that
can be found from the color sub-carrier frequency by: (44 Cs)/35 =
4.5 MHz.

Using a "3.58 MHz" color TV crystal, it's possible to use 17 flip-flops
in a set and reset depending on states of stages 4, 16, and 17 to
achieve a 60, 50, or 100 Hz precise output. That's done in the old
National Semiconductor MM5369 divider, a little 8-pin CMOS DIP
that runs on 5 to 15 VDC single supply, crystal oscillator active
circuitry on-board. If one can still find them, the following suffixes
will produce the following outputs with a colorburst crystal:

MM5369AA - 60 Hz
MM5369EYR - 100 Hz
MM5369EST - 50 Hz

Couldn't find the 20+ year old notes on the division presetting so all
I've got for those is a 1980 National MOS Databook (which doesn't
say squat about the divider chain's details). It's an interesting game
on paper with a calculator to figure out the exact division value. :-)

That little oscillator-divider was used in several Russian "Woodpecker"
(over the horizon radar) blanker add-ons for receiver two decades ago..
Some additional decade dividers coming off the output would get down
to the Woodpecker's impulse rate.

Len Anderson
retired (from regular hours) electronic engineer person