> In all this clatter about random parasitics, big bangs
> the like, I'd like to ask a question. I don't want to
> get into a piss 'in match or anything but all this talk
> seems to be centered on high power RF amps and
> it seems to me that this same so-called parasitic big
> bang problem should have been present in the
> tube exciters of old. The Drakes with the sweep tubes,
> the crappy old Swan's, Heathkit's, Hallicrafters,
> should have all had big bang problems except maybe
> with a smaller bang yet it seems these rigs got by with
> stanard design procedures in the final compartment.
> Just a thought......
> Mark WB8JKR
Allow me to suggest several factors that have exacerbated
the "big bang" problem over the years.
!. The scaling down problem. Sacrificing fair to good layouts
for a more compact product with less robust components.
2. Going from 5 bands to 8 or 9 in a very small box is a tremendous
feat in itself. This presents a very large invitation to disaster.
Components and their layout become many times more critical.
Going from 5 band Pi networks to 8-9 band Pi-L networks,
usually in the same space or less has created a great dumbing
down of design. One cannot blame manufacturers for this entirely.
The "modern" ham is demanding a legal-limit, all-band amp that
can be carried home under one arm, and God help the manufacturer
who provides a blower that is any louder than a field mouse
urinating on a cotton boll.
3. Ever-rising requirements for higher plate voltages in the newer
generation tubes now on the market, while still maintaining
cabinet size where 2000-2500 volts previously resided. Going
from 3000volts to 5000-6000 volts Ep is not a linear increase in
design criteria; it is exponential.
4. Starting with Drake et al, producing exciters with power over-shoot
at key-up, combined with QSK, VOX and the popularity of the
digital modes have created new means to punish amplifiers at
each mash of the key.
5. Although most hams may be willing to pay $40,000 for a new Ford
truck, they began to balk in the mid '80's about paying for tank coils
wound with big tubing, vacuum variable capacitors, power supplies
with one oil filter capacitor, tuned filter chokes, and 20 amp band
switches.
The amp problem is not unique in the U.S. market place. One law of
economics that still remains in place is that you usually get what you
pay for.
(((73)))
Phil, K5PC
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