"Keyboard In The Noise" wrote in message
news:n%2yc.34114$tI2.12543@fed1read07...
Can any one point me to a good expalnation of why PSK31 should be operated
at low power ???

PSK-31, more so than most modes, requires that amateurs respect each other's
need to communicate. It is a very narrow band mode, and requires
astonishingly low power to be effective. PSK is even more narrow banded
than CW. The narrower the bandwidth, the less power you need to make it
above the noise. Furthermore, on PSK, the DSP algorithms are good enough
that you only need to be barely above the noise for 100% copy. Once you
have achieved 100% copy there is nothing to gain by having a stronger
signal.

Most amateurs use SSB rigs on PSK. Unlike CW, where a sharp filter can keep
a strong station out of the passband (and out of the AGC), on PSK the entire
PSK band is one SSB signal wide. If there is one strong station, that
station is going to prevent everyone else on the band from hearing their own
QSOs. Running 100 watts on PSK is the very definition of a LID.

Have heard for a 100 Watt rig keep it throttled back to 35 Watts also
heard
50 Watts.

35 watts is probably tops for most conditions. A good operator will keep
his power well below that, and only crank it up to 35 or so when conditions
are truly horrid.

I think it has to do distortion if higher power is used

Most SSB rigs can't deliver full power continuously. They are rated for peak
power at a very low duty cycle. Many will toast their finals at 100 watts
continuous. Depending on the rig and how you make the measurements, many
cannot make more than half power without distortion, and distortion on PSK
is a very bad thing. But this should be a moot point anyway. Most of the
time you should be able to make the contact at a watt or so. Sometimes you
may need to crank it up to 5 or 10, but if you need a lot more than that,
something is very wrong. Most likely, some other LID on the band is running
100 watts.

Sadly, PSK seems to be experiencing the sort of power warfare that makes 20
phone such an awful place. A few years ago, it was rare to hear a station
running more than 2 or 3 watts. Now it seems like 20 is a lot more common.
Unfortunately, a lot of 20 watt stations means that other stations need to
run higher power, too.

I am speaking here of 14 MHz and up. On the lower frequencies, especially
3.5 MHz, there is a need for a little more power. But at 14 MHz and up, the
only reason to need more than about a watt is because QRM from stations
running too much power are interfering with the receiving station.

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