Rev 1.01
6
5. Ultimate3S configuration
This section applies if you are using the full 5W HF PA kit assembly, including the raised cosine
envelope shaping.
The Ultimate3S requires at least firmware version v3.12.
There is a configuration screen as follows:
Shaping {ms Max}
05 115
The first parameter is the rise/fall time of the raised
cosine envelope that will be generated. In this
example it is 5ms. Rise/fall times of around 5 to
10ms are common in commercial amateur radio
CW transceivers.
The second parameter is the maximum value to
send to the DAC. A safe value would be 115 for a
12V supply or 140 for a 13.8V supply. Please refer
to the PA Assembly instructions, section 5.3, for an
explanation of this value and for values that suit
other PA supply voltages. If you have an
oscilloscope you can experiment with different
values.
The ‘scope screenshot (right) is a perfect raised cosine 12wpm CW dit with 20ms rise and fall times.
If the “Max” value is too high (above left), then there will be clipping (a sharp corner) at the start and
finish of the transmission, and there will be a delay from key-up to the decline of the RF envelope. On
the other
hand if the “Max” value is too low (above right) then the envelope will have a nice raised
cosine shape but will have a reduced amplitude (power output).
