Tuesday, May 31, 2016

DDS Buffer

In order to see if I could get better readings on the antenna analyzer, I built this DDS buffer circuit from here.

First go of this I forgot the output cap, and when I hooked it up to my 50 ohm dummy load, I was getting 6 volts peak-to-peak.  I blinked a few times, confused, then checked the transistors.  HOT!

After the cap was added, it gave a more reasonable 3 volts p-p.  Not the prettiest output in the world - the first harmonic was pretty strong - but amplified.

I tried hooking this up to my antenna analyzer circuit and measured the result on the dummy load.

Hard to really see what is going on here, but it is DDS->Amp->Analyzer->Dummy load.  I'm still not seeing what I expect, though - the readings actually look worse.  I guess it could be that strong harmonic, not sure.

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