Hello Peter,
:From: Peter Sundberg <sm2cew@telia.com>
:Gents,
:It seems to me that no matter what anyone say's or present
:about a DAF amp it is constantly being contested by the wise guys.
This wise guy contested the signal I heard on 40 meters an
adequate distance away, where I shouldn't have heard him.
The typical round table with this gent had 8 other people, most
running big amplifiers. I didn't hear much of anyone else. I moved
down another few KHz and he still hosed up my conversation.
It's fortunate that the operator is a really nice guy (and longtime
friend) and took the amplifier off line when I brought it to his
attention. A later conversation with him got me a copy of the
screen control circuit he used. Maybe you guys would like to
see it on the sonic server later this next week..? His heart is in
the right place, his signal was not.
:On the other hand, Rich can say that he once heard a "DAF"
:amp that sounded bad and everyone is then certain that this
:is the truth, un-contested. No matter the guy who ran this
:so called "DAF" amp turns out to have his own "Dude-circuit"
:to produce the doo-doo.
Twas I who mentioned Norms amplifier, both Rich and I had
many a conversation with Norm about the circuit. Rich convinced
him to retrofit his circuit with something more conventional.
Since I know what he used, let me tell you what was involved.
A portion of the drive signal was used to control the screen
current potential. His notes to me were for a dual 4cx250 amp.
The circuit details show most of the work done with solid state
devices although a tube equivalent was available.
I'm under the impression one daf circuit actually uses rectified rf
for the applied screen potential. This seems a rather odd arrangement
to me as a portion of the actual rectified drive supplies the screen
power. Norms circuit was a pair of hv transistors used to control
the screen potential from a power supply. The circuit is a much higher
z load on the drive source vs the daf circuit I've seen on the web site.
Would this change the end result..? The dynamic screen potential is
the tell-all. Both designs would probably place lots of "el torro
poo-poo"
in my receiver from 4KHz away. Norms did from Southern California to
my QTH near Sacramento... a few hundred mile distance. The
local HF CB'er's do it from 3 blocks away.
:Running a DAF amp for a couple of years now I can say that it is good
:design and I get NO complaints for splattering or sounding bad. (Using a
:similar tube as in SM3BDZ amp, a QBL5-3500)
If your blowing holes in the band, others might think you just
another contest operator. If I heard you on the bands, I'd say
something quick. Reference "The Emperors New Cloths" for
a similar example. (Han Christian Anderson) Sorry, I had to
say that at least once in my life...
:Lars, SM3BDZ and Petter, SM3PXO has proven the linearity of the amp by
:presenting plots on the Lars's webpage. We have used our amps on the air
:for years without complaints. Can't you guys accept that... ??
Plots didn't hold water for Norms circuit when we told him what everyone
was hearing <4KHz away. Other than a few amateur circuits, why hasn't
the daf circuit caught on in the market place..?
:I think the DAF amp will be the Amp of The Millenium.
:/Peter SM2CEW
"Read my lips, no new taxes!"
skipp
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