Push-Push Jfet amplifier with parallel inputs and a Toroid output
transformer, no secondary along with a
simple filter using a 10 MHz series resonate crystal connected to one drain and
an adjustable capacitor connected
to the other would work fine. You connect the other ends of the two together
and a loading resistor to ground.
The capacitor is used to neutralize or null out the shunt capacitance of the
crystal so that a capacitive path
for the other frequencies , 5, 15, 20, etc is eliminated. Then follow up with
your linear class A amplifier.
The loading on the output of the crystal filter will determine it's Q and is
not real critical, but should be
perhaps around 10-100 times the series resistance of the crystal. Since most
readily available crystals
are not exactly on frequency a lower Q, higher R would be desired, but that
will not greatly affect the
5 MHz or undesired harmonic attenuation. Perhaps one or two kHz bandpass would
be just about right.
Just don't overdrive the crystal. Also, for the price of $1 or less you may
get 10 or so for further experimentation.
This combination of doubler and crystal filter should provide a very nice
sinewave output
73
Bill wa4lav
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