Hi all,
I may be wrong (and please correct me if), but:
For the dependence of the anode current (variation) in respect
with the anode and grid voltages for a good SSB tetrode
(see data sheet), you will notice that these characteristics are
almost parallel with the anode voltage reference line, especially
for medium and higher anode voltages area.
It mean that, for a constant grid voltage, relatively large variations
of the anode voltage tend to small changes for the anode current
(so, the anode voltage have less influence for the anode current).
This is normal for very high gain tubes, as the amplification is
defined by the report of the anode and grid voltages variations
that produces the same variation of the anode current respectively.
Of course, we are not talking about extremely large anode voltage
drop that can tend to limiting and high screen current (and distortion)
and insufficient "working space" for the tube (as can be seen for
the lower anode voltage region).
This is why Rich is right.
The same is not true for low/medium gain triodes, for which the
anode voltage have a larger influence to the anode current,
and these tubes are not very good for linear amps also
(are not very "linear").
Compare the 4CX1500B or the 3CX800 (very "linear" and high
gain tubes) characteristics with the ones for the TB3,5/750 or
TB4/1250 (medium mu triodes, european made) for example,
and will notice the differences, especially for the higher anode
current area.
[Very "linear" is equivalent to low IMD].
73's,
Traian
Rich wrote:
> >Hi Rich,
> >
> >Interesting. This seems to go against what I'd intuitively suspect, but
> >then, my intuition is often in error. I certainly understand why a
> >regulated screen supply helps linearity, but why wouldn't a regulated B+
> >supply help, too?
>
> Because a tube's linearity does not change much even a 25% anode-V change.
>
> >Ideally, wouldn't we want everything to be regulated
> >(stiff as a board) for best linearity? Or, does a very stiff (regulated) B+
> >simply not help *enough* to be worth the hassle?
> >
> bingo
>
> >73,
> >
> >Kim
> >
> >At 08:17 PM 10/29/2002 -0800, you wrote:
> >
> >
> >> >I recently ran across an article in QEX that describes how to build a
> >> >regulated HV supply for large amplifiers. Aside from cost and complexity,
> >> >is there a good reason to avoid doing this? If so, what? It seems that
> >> >overall linearity would be enhanced in the supply were regulated (an
> >> >argument also made in the article).
> >>
> >>Regulated HV does nothing other than improve pep during berserko speech
> >>processing. Regulated anode supply V does not improve linearity.
> >>However, regulated screen V does. I built a regulated 6kV supply. It
> >>was as useful as teats on a BULL ELEPHANT.
> >>
> >>
> >> >...
> >>
> >>- Rich..., 805.386.3734, www.vcnet.com/measures.
> >>
> >>_______________________________________________
> >>Amps mailing list
> >>Amps@contesting.com
> >>http://lists.contesting.com/mailman/listinfo/amps
> >
> > Kim Elmore, Ph.D.
> > University of Oklahoma
> > Cooperative Institute for Mesoscale Meteorological Studies
> >"All of weather is divided into three parts: Yes, No, and Maybe. The
> >greatest of these is Maybe" The original Latin appears to be garbled.
> >
> >
>
> - Rich..., 805.386.3734, www.vcnet.com/measures.
>
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