Mike wrote:
> I seem to remember reading someplace that the final Transistors used in most
> 100 watt rigs are do not give a very clean output at 10 watts or so, 25
> watts and up the output is clean, now this normally would not make any
> difference if you were just running 10 watts QRP because no one can hear
> you. But, when you amplify that 10 watts with an external amplifier then
> who knows how it may spatter across the band. Anyway just a thought, if you
> have a Scope it might be worth taking a look at the signal.
>
>
It's been quite a while since I was involved at that level, but I think
that would be dependent on the particular transistor(s) and the circuit.
The curves for the 2SC5125 transistor listed as the two finals in the
Icom 756 Pro III look to be fairly linear even in the low end. However
the impedance running 10 watts versus 100 watts out it's designed for
should change considerably with a fixed network. I'd think that would
create quite a mismatch. Those are rather impressive transistors rated
at 80 watts out each into an SWR as high as 8:1 at 175 MHz. So running
the Pro III at the full 100 watts gives a large safety factor. That
being the case, with the Pro series I'd not give a second though to
running the thing at full power.
OTOH I'm surprised to see transistors rated for such a high frequency
used as low as 1.8 MHz. In "the old days" VHF transistors didn't do
well at the low end of the HF spectrum. Of course back then we also put
a string of resistors and caps across a string of diodes, something no
longer needed.
73
Roger (K8RI)
> Mike
>
> -----Original Message-----
> From: amps-bounces@contesting.com [mailto:amps-bounces@contesting.com] On
> Behalf Of Ken Bills
>
>
> While RTTY contesting this weekend, I wondered, since my amp still was
> warmed up, if it made sense to run the Alpha at 100 watts output, versus
> pushing the exciter at it's 100 watt limit. It only required about 9-10
> watts output, to deliver the 100 watt contest limit.
>
>
>
> I am sure this doesn't help my carbon footprint, but it may save the finals
> in the Icom ProIII.
>
>
>
> Any thoughts?
>
>
>
>
>
>
>
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