[Elecraft] QRO/QRP (WAS: Tube Linear Amp design for basic K2)

[Ron D'Eau Claire]

Robert G3RCE wrote:
I was surprised that you mention using 400w on PSK31

I've never seen anyone mention using more than about 70w on PSK31 as  
high powers are not supposed to be necessary?

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Truth be told, one can work the world using 5 watts (or less) on CW too, but
what percentage of our fraternity do that? 

Why use QRO? Because it's there! It needs no further justification by most.
And, on occasion, it'll pull through copy where copy isn't possible at lower
power. 

Whether QRO is really "needed" or not is a whole different issue that
changes from moment to moment. For better or worse, virtually every Ham I've
met runs max power almost all the time. The only exception are some with
kilowatt amps they do occasionally turn off. Still, how often do you hear
someone say, "PSE QRO" or, if sig reports run 599, "PSE QRP"?? 

Actually I'm a bit of a stealth QRP operator. If I get a 599 report, I'm
very likely to turn the power down by half, no matter what I'm running. Then
I'll just ask if my signal is still FB. If so, I might cut it by half again.
Each halving is about 1/2 S-unit so if I do it twice my signal is down an
S-unit on  most receivers. Most of the time that's barely noticeable. It
works the same if the initial power is a kilowatt, 100 watts or 10 watts.
One of the interesting operating gambits many QRPers enjoy is to QRP
together during a QSO so see "how low they can go". The results are often
astounding, getting down  into the milliwatt range with perfect copy. 

One of the issues with PSK is that most software includes an AGC function to
keep the audio levels in the soundcard under control. A really loud signal
will then suppress the gain and mask others since most PSK operators use
wide-open I.F. bandwidths so they can see all the nearby frequencies on the
waterfall display. 

That's how some of us like to operate CW using wide bandwidths and letting
our ears to do the filtering. And we've learned that one can't run AGC doing
that if there's a very strong signal in the passband. More and more PSK
operators are discovering the same thing, whether it's a 5 watt signal from
next door or the kilowatt farther away. 

As more QRO shows up on PSK, PSK techniques will have to change too: either
filter out all but the one signal being received in the I.F. or by using
limiting or some similar process like those of us who like wide-bandwidth on
CW use. 

Ron AC7AC