Signal Generator as a VFO..

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Signal Generator as a VFO..

Postby N3LRX » Sun Feb 11, 2007 2:23 pm

I have a CONAR 281 Digital Signal Gen. (Solid State not the older drifty model 280)
I've been letting it sit there and burn while I monitor it's stability with a freq. counter and it's quite stable.

I am wondering of there is a way I could build a buffer amplifier and then use an op amp to create the two phases to feed a QIX 500. Or could I get away with something as simple as a buffer amp and an input transformer to drive the DEIC420s?

It looks allot cleaner than the bastard job I did at breadboarding the QIX VFO.
73 DE Randy N3LRX
You can't spell HAM without AM!
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Postby kf1z » Sun Feb 11, 2007 3:50 pm

I slapped together QIX's VFO...

Looks like a dogpile, but works well.



You can take any sinewave signal source, and turn it to square wave...

Look at the vfo schematic...(QIX)

There's a transistor there that taps off the vfo coil...
Basically a 'class e ' waveform at that point....

Which drives the J-K Flip-Flop fine.....

So, your biggest concern is terminating your signal source, and using the same scheme to drive the flip-flops
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Postby frank carcia » Sun Feb 11, 2007 8:49 pm

I use an old HP VHF signal generator as a source for my 160 meter Rig,
I let it warm up for a while and it is fine. I took an 11C90 divide by 10 prescaler into a 74AC74 to generate the two phases. The generator runs at X20 frequency.
an old Collins PTO makes a nice VFO. The one from a T195 tunes 1.5 to 3 MHz. It can easily be converted to solid state.
The trick in building a nice VFO is finding a high quality tuning cap.
I've collected a number of nice ones over the years with gear drives and well machined bearings. The best comes out of a BC221 .
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