At 22:42 12/01/2003 +0100, you wrote:
guess many of you built the G0MRF-Quarter-Kilowatt-Amplifier.
I did. the PSU is not finished yet.
got some trouble with the phase of the 137kHz sines
(es triangular and rectangular) measured at the gates of the MOSFETs.
there is a diff btwn the two channels of estimated 10degr.
that means parasitic oscillation if operating the PA, doesn`t it.
Assuming this is G0MRF's linear PA, the circuit is completely symmetrical.
So if there is any phase shift in the drive circuit, the drive waveforms
will be phase shifted by the same amount by the time they reach the gates
of each MOSFETs. So the drive waveforms should always be 180degrees out of
phase unless one of the components on one side of the circuit is different
from it's counterpart on the other side. I would start by checking that all
components on the input side of the circuit are correct.
Another possibility is that the circuit is OK, but the scope is not
triggering correctly - this sometimes happens if the scope is set to
"mixed" trigger, if it has this setting.
Cheers, Jim Moritz
73 de M0BMU