Re: VFO Output – Is This Right???
James Daldry W4JED
First - what is the bandwidth of the scope you are using? To properly see a square wave the scope cutoff frequency has to be at least 5 times the fundamental frequency of the signal.
Next - how is the probe grounded to the source? If you are
looking at signals of more than a few megahertz the ground should
be a short wire wrapped around the ground ring on the probe and
soldered to the ground side of the output connector on the device.
Even a couple inches of wire is too much. It will add the
overshoots that you are looking at.
Next - are you using a X10 probe? While the cable into the scope is coaxial, it is not terminated with a 50 or 75 ohm resistor inside the scope unless it is specifically made for looking at 50 or 75 ohm systems. With a 50 ohm impedance at the input and a 1 megohm resistance inside the scope the cable will ring like a bell. Using a properly adjusted (!) X10 probe will disconnect the input capacitance of the scope from the signal generator and make the display truer. If you don't know how to calibrate the probe, read the manual.
On 6/21/19 2:40 PM, pietromartini2007@... wrote: