Friday, December 26, 2014

XOR gate mixer, vu2dev

The XOR gate pre-mixed oscillator mixer,
There are many mixer available for radio amateurs RF work i.e common diode mixers, transistor, IC, DBM, some specialized IC, they have their own advantage and dis-advantage. Sometimes you just need a single frequency devied out of two crystals...... a pre-mixed oscillator...                 
VU2DEV, (Dev Rama Prabhu) recently published this circuit by taming the nasty little XOR gates. He reasoned that PLL has xor gate why not try it as a mixer. He made it. I likes so requested for the circuit diagram. After two days, provided me a handdrawn schematic with a remark that he wanted to test it at least 2 - 3 times, so its repeatability, consistent results, characteristics can be predicted. (26dec2014)


Here on veroboard has two IC sockets. He tried it with two different set of xtals before giving me the ckt to test the repeatability. Only one IC is used for one mixer. LM7805 is used for voltage regulations. (A must.)
We need to put a tuned amplifier to filter out the  harmonics and unwanted spurious frequency products. Remember it is still a digital ckt (squar waves reach with harmonics). @2dev has put a LC tuned class-a amplifier. Not shown in the ckt diagram. See the second picture, the transistor Amplifier is on the copper plane.
My friend Om Jishnu has also made this ckt with success. I have to try this out. This digital gates will save me from ,using the hard to find little obselotte TA7358 mixer ic. see my previous post on this ta7358 mixer. They are good, but if you can do more with less component, in a simple way, why not give it a try... You will sure to love the result. Build process and other data will be updated later on....
When time permits, build it & update my own pictures giving my own twist...... till then ENJOY ( the wheel is running ,re-invented by 2dev)

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