[Elecraft] Question on PSK Power Level

[Don Wilhelm]

Parker,

The real concern is for the junction temperature of the output transistors.
The K2 will safely do 10 watts or more intermittent duty - but with digital
modes, the maximum power out must be derated since these are continuous duty
modes.  Cutting the power by 1/2 is a usual 'rule of thumb'.

It really makes little difference whether you reduce the power by reducing
the soundcard levels as you seem to be doing or by reducing the RF level by
backing down on the K2 power control and driving the soundcard outputs a bit
higher- it all accomplishes the same thing, but your method could result in
lower IMD because of the lower levels in the audio/modulating chain.

There is a 'mental' danger that if the power output is set for 10 watts,
some folks seem to want to see 10 watts on the wattmeter.  It sounds like
you 'have your head on straight' and are doing things properly by looking
for only 5 watts out.

73,
Don W3FPR

----- Original Message ----- 

> The (QRP) K2 manual instructs us to set the power level at 5
> watts or less for digital modes.  The few times I've had the
> rig on PSK, I set the power control to 10 watts and adjust
> the actual power output using the sound card output level.
> My question is regarding the 5 watt value.  If I put the rig
> in transmit using the Pause/Break function key (Digipan
> software) , I get the two warbling tones.  If I adjust to 5
> watts in this mode, I'll see an average of 5 watts out while
> transmitting.  If I use the tune function in Digipan that
> generates a single tone, however, I get a solid 10 watts
> out.  This seems to fit the admonishment that digital modes
> result in almost 100% duty cycle.  In other words, my 5
> watts while warbling away is equivalent to a continuous 10
> watt duty cycle, right?  Or, should I adjust for only 5
> watts with the single tone, resulting in seeing only 2-3
> watts out while actually transmitting?  Wattmeter is
> standard WM-2.
>
>