Minimising stray RF ouput from the modulator.
Inline Low Pass Filtering before feeding the amplifier.
Ensuring a clean signal reaches the PA input.
Digitally derived output signals can be full of other signals and harmonics, that need to be minimised if we wish to operate within ACMA required guidelines. It is also courteous that we do not produce extraneous interference to other users in the band or nearby bands, whether amateur or commercial users.
Mark from Mini-Kits offers a 7th order Chebychev low pass filter that is ideal for this band and at a great price. I have bought, built and used one in my setup, to clean the output of my modulator and used as a 70cm pre-filter into my PA. See link below for kit details.