I am very often surprised that most amps on the market are allowed to be
sold at all. In a compact box used in your private home, you have dangerous
voltages that are isolated from your family and yourself only by a, very
often, tiny underrated anode-to- pi-filter coupling capacitor. If your
protection rfc is kaputt, your 2-4 kilovolts are avaiable to your antenna(s)
and the people near them. With the hams technical knowledge going down, as
it has the last 30 years, its surprising that so little accidents have
occured. As the components are severely underrated from a safety point of
view. The day when amps have to be inspected and tested by some official
safety inspector, that day very few amps will be sold at all, I am sure.
Yes , yesterdays amps were much better. Used much better and bigger
components- even stronger than to-days amps with double the power than
yesterdays.
Maybe they had also less tendency to oscillate at higher frequencies simply
( maybe - this is only a guess, please ) because tube gain was lower at
higher frequencies??? Did not EIMAC make several changes to the original
3-500Z with graphite anode that led to higher gain at higher frequencies?
When you insert a modern 3-500Z into an older amp, you maybe will get
parasitics because your amp was not designed for this modern tube? TL 922
??? Now, get me right, this is only a theory - I really have no definite
proofs. Only am guessing.
How come , by the way, that so many hams and their families survived their
high come-and- hit-me-lightning towers standing out from nearby high
objects? Is it not strange that so few direct lightning hits have happened?
Many secondary effects of course, but direct hits?
?????? de Hans SM5KI
>Från: "Phil Clements" <philk5pc@tyler.net>
>Till: <AMPS@contesting.com>, "Mark S Graalman" <wb8jkr@juno.com>
>Ämne: Re: [AMPS] Misc. Oscillations
>Datum: sön 5 mar 2000 16.57
>
>
>> 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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>
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