VFO Output – Is This Right???


I built the VFO/Signal Generator kit with no problems, and it started up right away. However, the output waveforms and amplitudes are not what I expected; according to the manual, they should be square waves with an amplitude of 3.3V p-p. Taking the output from the CLK0 pad, what I see on my scope is sort of a square wave at 3.5 MHz with a lot of overshoot and undershoot, and as the frequency increases the waveform becomes more of a triangle and the amplitude steadily decreases, until it’s only 246 mV at 150 MHz, and the waveform is almost a sine wave. I don’t have any load on the output, and I attached the scope probes directly to the CLK0 pads. If I had to guess I’d say stray capacitance may be the culprit. So can someone tell me if I have a problem with my build? I’m attaching a few photos of the scope images.

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