Examining the cited test results was not intended to prove that the G2DAF
circuit was a good circuit or that the stated Eimac specifications could not
be improved. It was merely intended to question the broad statement that
the G2DAF circuit was bad because of the example cited of -22 db 3rd order
distortion.
Frankly, I am not smart enough to know whether the G2DAF circuit is "good"
or "bad" without reading something that convinces me or doing tests myself
and seeing the results. So, at this point, I must leave my mind open to
accept facts and not close the door to the results or reasoning of others.
The G2DAF has some interesting advantages - not requiring a regulated screen
voltage and dissipating zero power at idle. One disadvantage, however, is
that since the screen is driven, more driving power is required which means
that the load on the driver may change and that could increase the
distortion of the driver itself.
So, after removing my 75 meter quad and replacing it with a Moxon beam,
finishing restoration of an Alpha 77SX and my Cosmophone, perhaps I will
make a G2DAF amplifier and find out about them.
I have learned to question statements and often my results are quite
different than the accepted results. An example of this is the dreaded
"phase noise". I have a spectrum analyzer and decided to examine the phase
noise of a few devices around the shack. I examined a home built crystal
controlled oscillator, an old military analog signal generator and a 20 year
old Slant Fin Phase Lock Loop signal generator. My idea was to find out how
bad the Slant Fin was. To my surprise, the unit with the most phase noise
was the crystal oscillator. The next noisiest was the analog generator and
the cleanest was the Slant Fin using old technology. Upon further review, I
realized the crystal oscillator was noisy because it had a warping capacitor
in it. I remembered that when I built a low noise crystal oscillator for a
converter to receive signals off the moon I ended up 700 cycles from
calibration because I could not use a "rubbering" circuit. So, now, when
someone makes a blanket statement that the new rigs are bad because of phase
noise, I question it.
In fact, I question almost anything - except President Clinton and my wife.
Colin K7FM
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