Bill, W6WRT wrote:
> 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.
>
With full carrier and full output, you can also adjust the ALC so it
just becomes active. Then when talking keep the drive down to the point
where you are just under where the ALC becomes active, but don't use the
ALC to limit the output or it'll really splatter. This is particularly
important with SS amps.
It's also the way some commercial amps recommend you keep track of the
signal level.
73
Roger (K8RI)
> 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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