[1000mp] Mark V Class A operation

[Rob Atkinson, K5UJ]

I looked through the ft1000 yahoo group for the
post about class a operation and could not find it.
maybe someone else can explain
why when in class a, the pa runs cooler with more power
rather than less.  I just remember this engineer saying that
but i could not begin to repeat why.  anyway, i think if
that is true, there are class a failures because hams don't
understand or realize that, and when it gets hot they crank
down to power thinking it will run cooler and make things worse
instead.

73,
rob/k5uj



----- Original Message -----
From: "Rob Atkinson, K5UJ" <k5uj at mc.net>
To: "All about Yaesu 1000mp" <1000mp at mailman.qth.net>
Sent: Sunday, August 29, 2004 8:41 PM
Subject: Re: [1000mp] Mark V Class A operation


> I am not an expert.  I have heard of people frying the pa in class a
> operation.
> A friend of mine and I tried class a and the heat sink got hotter than we
> felt
> comfortable with so we abandoned it.  I have heard of people blowing the
pa
> when cranking the collector current pot (power pot on the front panel) all
> the way
> clockwise and yacking away in class ab.  I have always run mine a little
> below that.
>
> Now you know where I was a few weeks ago.  I (or maybe it was someone
else)
> asked
> something related to this on the yahoo group for yaesu and a guy who
seemed
> to be
> very knowledgable about RF design said that in class A, you actually do
more
> damage
> running at low power, and you stand a bigger chance of frying
> the pa if you dial back the watts in class A, which was what we had done,
> thinking less
> watts, less heat.  We noticed that running the rig in class A at 30 watts
or
> so didn't make a
> difference; it still got real hot.  Besides, for me, that would not help
> because my amp needs
> at least 75 w. to be driven as it is not one of these ceramic tube screen
> driven amps.
>
> he seemed to think it should be run at 75 watts.  i did not understand
> it and it is a paradox of class A I guess, and decided to stay with AB to
be
> safe.
> if I can find his explanation I will try to send it.
>
> rob/k5uj
>
>
>
>
> ----- Original Message -----
> From: "Jim" <pywacker at fuse.net>
> To: <1000mp at mailman.qth.net>
> Sent: Saturday, August 28, 2004 12:28 PM
> Subject: [1000mp] Mark V Class A operation
>
>
> > I have heard some hams on the air (just a few) along with some limited
> > posting on some boards about the use of the class A feature of the Mark
V
> > contributing to the loss of finals in these rigs. Any real truth to this
> > statement?
> >
> >
> >
> > Thanks, Jim
> >
> >
> >
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> >
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