Unfortunately that approach degrades the phase noise floor due to crystal dissipation limitations as well as degrading the phase noise in the flicker region due to the crystal itself,Not only is a clean (harmonic and subharmonic free) sine wave desirable so is low phase noise.Thermal drift of the crystal filter phase shift will also be problematic.Cascaded low Q filters suffer less from this than a single high Q filter. A low pass filter combined with series resonant shunt traps will have fewer issues with phase instability at 10MHz than using a 10MHz bandpass filter.
Bruce On Wednesday, 4 February 2015 9:53 AM, "Fuqua, Bill L" <wlfuq...@uky.edu> wrote: 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 _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.