[Elecraft] Data mode and filters

[Joe Subich, W4TV]

 > 50W gets a legal limit amp to full power.

Only with some solid state a and ceramic tube amplifiers.  Many of
the glass tube amplifiers need every one of the 100Wto reach 1500W
PEP output.

> Given that the vast majority of PSK31 ops work below 50W and that 50W
> to a power amp will get you to 1500W, your concerns simply do not
> make sense in the real world.

You are extrapolating the behavior of the K3 with its open loop ALC
and reasonably behaved KPA3 to other rigs.  The results would be
very different if you were pushing a "12V" Icom, Kenwood, or Yaesu
rig.  All of this still requires the user understand the concept
of "crest factor" and use a wattmeter that properly indicates peak
power.

73,

   ... Joe, W4TV


On 2015-05-18 3:26 AM, Jim Brown wrote:
> On Sun,5/17/2015 7:29 PM, Joe Subich, W4TV wrote:
>> Yes, you were probably over driving the K3 (KPA3).  You can estimate
>> the amount of overdrive by using the the LP-100A Peak to Average
>> function.  With PSK31 "idle", the LP-100A shows the following:
>
> Perhaps, BUT -- look at the data for 100W, 93W, 50W. and 29W. The 100W
> and 93W data clearly shows IMD at levels corresponding to 2-tone data,
> the difference between 100W and 93W is 4 dB, and at 50W almost no IMD is
> visible (there are sidebands +/- 360 Hz 60 dB down). 50W gets a legal
> limit amp to full power. At 30W, which gets the KPA500 to full power,
> sidebands at about +/- 50 Hz are barely visible, there are -63 dBc
> sidebands at about +/- 360 Hz.
>
> But let's return to the real world issue -- QRM as the result of
> excessive occupied bandwidth. The K3 I measured is 105 Hz wide at -40
> dBC at 29W, 110 Hz at 50W. At -60 dBC, it's 340 Hz at 29W and 720 Hz at
> 50W.
>
> Given that the vast majority of PSK31 ops work below 50W and that 50W to
> a power amp will get you to 1500W, your concerns simply do not make
> sense in the real world.
>
> 73, Jim K9YC
>
>
>
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