R: R: [AMPS] You gotta read this....

[Maurizio Panicara]

(see below)

-----Messaggio Originale-----
Da: Jeff Wolf <da_kang@hotmail.com>
A: <i4jmy@iol.it>
Cc: <amps@contesting.com>
Data invio: giovedì 14 ottobre 1999 21.04
Oggetto: Re: R: [AMPS] You gotta read this....


> >>>The output power doesn't matter as to whether the maximum output is
> >>>carrier level or PEP.  1Kw is one Kw, and when you are doing 1Kw CW,
you
> >>>are also doing 1Kw PEP.

Really ?
Can you explain us how can we measure peak power instead of the carrier with
an RMS power meter ?


> Often, the real curves of the tubes differ consitently from those
deductable
> by the graphic of constant current ones on data sheets, and a single tone
> power is a different story than a carrier level.
>
> >>>Technobabble.  Let's get on with the story.

Are you sure ?
Have you ever tried to draw static curves in a zero bias tube like a
3CX15000 varying catode voltage and
measuring Ip ?

> You would fall into that category on this subject.  You may know GREAT
> design for RF, and you may be able to build a large amplifier, but you
know
> NOTHING about the "Controlled Destruction" that the average 11 meter US
> operator subjects his equipment to.


Then I'm happy to be ignorant in that.
I never found a job or some aspect in amateur radio where I was asked to
design or check something voted to
self destruction.

>
>
> In other modes like FM, a wattmeter wouldn't read ever 36Kw of carrier
power
> because that level is well over the tube capability and (reasonable) gain
> already went away at much lower carrier output.
>
>
> >>>Your saying that a 4CX15,000 wouldn't produce 36Kw of carrier power on
an
> >>>FM signal when being hit with 14 Kilovolts on the anode, and far
> >>>exceeding the grid current rating grid driven?
>
> I think you better go back to electronics 101 if that is the case.

Grid driven ?
A 3 x 8877 PA to grid drive ?
Can you explain ?

>
> Let's suppose reasonable a 10 dB gain to have 15 kW for each tube, the
> required drive power would be 1.5 Kw and the claimed 3 x 8877 could
largely
> meet requirements for 30Kw (two tubes).
>
>
> Never, (even overdriving a lot) is possible to get twice that output
(60Kw)
> in term of carrier power with that configuration and those tubes.
>
>
> >>>BS.  It is done all the time in the Ghostrider and Bluegill amplifiers.
>

Did you ever try yourself them or do you report someone else points ?

.
>
> And, we don't use three tubes, we use two.  The 3 tube amplifier is an
8877
> box.  Personally, I don't like the 8877, but that was the particular tube
> that was used in this amp...  I am partial to the 3CX1200 myself.

What's wrong in the 8877 ??

>
> Another point, a tetrode operated in GG doesn't differ substantially from
a
> triode in term of efficiency
>
> >>>And what is your point here?

Like "Paganini", I dont' repeat again it's written.

>
> and 3 x 8877 would be a total nonsense in a grid driven amplifier.
>
>
> >>>You really think so?


If nothing changed in the last days, grid driven is an approximation of a
voltage drive.
Can you explain how do you calculate the needed driving power in a common
cathode amp ?


> All the story looks as the fishermans' story (the real fish is much
smaller)
> or as something developed by someone with electronic bases but following
> conventional behaves
>
>
> >>>I don't deal in the conventional...  I deal in the real and
experienced.
>

Me too.

>
> and the readings of data sheets rather than a mere report of real facts.
>

For me and many others, this is often in contrast with the previous
sentence.

>
>
> >>>Well, next time you are stateside, I would like to take you to a
> >>>"keydown" event.

I think I'll be there for Dayton 2000, for the Hamvention.

>
> And that goes for anyone on this reflector....  Interested or not, it is
> fun, and for the stuffed shirt types, it can be eye-opening.
>
> Concerning the reported corona effects, they may happen at nearly any
power
> depending by used antennas and enviromental conditions.
>
>
> >>>Yes, and the world is flat, right?


No, the world it's a three dimensional object but for a number of reasons
any other shape might is good time to time.

A short but loaded antenna can behave as an autotransformer. The antenna
edge can spark in the air because of an high voltage and the voltage depends
by the impedance. Not necessarily the voltage creating a corona effect is
due to an abnormal power.
Do you want to bet on it ?

73,
Mauri I4JMY







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