> >In that case, lower series resistance means higher Q in the
> >system.
>
> ** True, but high series resistance produces low parallel-equivalent
> resistance, which lowers amplification. [Ref. figures 12 and 18 on my
> Web site]
Sorry Rich, that is not true. I don't expect you will answer this point by
point, but it would be interesting if you could refrain from insults and
smoke screens and try responding point by point.
First, there are a few meanings of Rp that can confuse people, so I'll say
what is what when I use Rp to avoid confusing anyone.
You claim lower Rp means less VHF gain. Lower Rp (plate load resistance)
does NOT mean less VHF gain, because of shunting reactances.
I can give a very clear example of this, that will help people who want to
understand the system picture it better. Consider an audio amplifier with
very high Rp (plate load resistance). It is well known that such amplifiers
roll off at high audio frequencies. The cure to high frequency rolloff,
outside of adding intentional gain compensating feedback, is to reduce Rp
(plate load resistance). This is because the shunting reactances of wiring
and the tubes actually roll off an amplifier's gain. This has always been a
big problem with broadband amps with tubes, especially big tubes. This is
why tube-type television sets had to use peaking coils in video amplifiers,
and why virtually no one could build a broadband tube amplifier with high
gain and high power in a single stage!
What we really want in a PA is to prevent low-loss resonances at VHF, or to
simply move those resonances to a different spot than where the control grid
is resonant.
This is where the problem with your hairpin suppressors, or small one or two
turn suppressors, comes in. Those suppressors have a very low Rp (parallel
equivalent resistance). This parallel equivalent resistance is what the
parallel combination of R and L "look like". It is in SERIES with the
impedance of the rest of the anode system. When that Rp (parallel equiv
resistance) is low, it allows the leads in external connections to have HI
Q.
Let me give a clear example of where you talk in a circle, this is pretty
easy to follow.
The AL1500 has a specific brass material used in the anode lead, for the
entire length of that lead. If I measure Rp (parallel resistance of that
lead, it is very low.
You claim your suppressors are better because they have low Rp (low parallel
resistance), and the anode lead system in the AL1500 has even less Rp
(parallel resistance)....yet you are especially critical of it. Why is that?
Why is GOOD when your suppressor has less Rp and especially bad when another
system has the same? The lowest Rp suppressor would be a dead short, or no
suppressor at all.
To anyone who wonders, different systems require different cures. If the
entire anode system can have low Q (such as being from brass) and moved to a
different frequency than the grid and if the self-neutralizing frequency is
made high enough, a PA can be made unconditionally stable without any
"suppressor".
The problem I have is you claim you are "lowering Q" in long skinny anode
leads by REDUCING the added parallel equivalent resistance placed in series
with the anode lead, which means you have reduced losses. The fact is, in
most cases your suppressors do the exact opposite of what you claim. They
reduce HF Q, while increasing VHF Q over stock systems.
This is why you got into such a nasty name-calling fight with N7WS and
others on an open forum, because they pointed this all out.
That still does not mean your suppressors will ruin amplifiers, because most
amps...once the real problems are fixed....behave very well. In some cases,
like in an amplifier unstable at HF, your suppressors could actually help
because they add HF loss. But there are a hundred ways to solve the problems
without adding excessive loss or lowering tank system operating Q.
73 Tom
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