ORIGINAL MESSAGE:
On Sat, 30 Jan 2010 15:42:21 +0000, Ron Youvan
<ka4inm@tampabay.rr.com> wrote:
>
> I've never related tuning with headroom and I don't get it. Tuning has
> always
>acted like and an adjustable attenuator to an amplifier's transfer
>charismatics.
REPLY:
Here's how it relates: If you tune up with a carrier of, let's say
1000 watts, and you tune for maximum power output, you will have a
perfect impedance match and greatest power efficiency. While this is
fine for CW, FM, RTTY or any full carrier mode, it is not the best for
SSB. If you are absolutely sure you will never drive it with anything
over 1000 watts, it will work for SSB too, but as soon as you go over,
even a small amount, you start splattering.
There are a couple of ways to ensure no splatter. The way I do it is
after tuning up, I back off the transmitter power a small amount. 2-5%
is adequate and will never be noticed at the receiving end.
The other way is, after tuning for max power, increase the loading a
bit until the output power drops off, again around 2-5%. Again, the
loss loss will never be noticed at the receiving end.
Inevitably, if you try to squeeze the last possible watt out of your
amp on SSB, you will splatter sooner or later.
73, Bill W6WRT
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