Hello again Friends,
The single FET amp which Steve lent me has been working fine, but if you
remember, during tuning the antenna system would come up with some weird
wave shapes. The amp uses an air core output coil. The antenna loading
coil , its matching coil and both coils in the transmitter's Low Pass Filter
are air core as well. So there is no iron in the working system.
Remember that when the antenna was tuned, one suggestion was to place a
matching transformer with TV Horizontal Ferrite core in the circuit. When
that was done, the waveform on the scope turned to garbage. (high in odd
order harmonics)
Today, the two FET amp which Scott lent me was put on the air. It has a
ferrite TV output core which I wound and even though it was placed at the
exact length of coax from the antenna which Steve's amp had been, it 's
output waveform is badly distorted.
It is important that I run the station at the maximum allowed IERP for the
sake of proving non-interference.
On Scott's amp, the current and voltage waveforms are identical and in
phase, the amp runs very stable at over 300 Watts input, but the waveforms
look awful. I have decided to switch back to Steve's transmitter and
revisit both the output of Scott's amp and the antenna system. I am
considering winding a air core transformer for it, but am unconvinced doing
so will solve the real problem.
I have a scopematch, and scope, an rf source capable of 18 kHz and up.
Any ideas on how to approach this waveform problem?
J.
|
