[Elecraft] PA with predistortion

[Ignacy]

Predistorsion properties are impressive. The following presentation

http://users.burlingtontelecom.net/~n1jez@burlingtontelecom.net/images/Eastern_VHF_UHF_Conf_2014.pdf

gives some information what is possible. In LDMOS amp with bias almost
reduced to 0, IMD3/5 change from -22/-28db to -55/-63db. Also a crappy 13.8V
CB amp with IMD3/5 of -18/-28 becomes -47/-53 after predistortion.

Class AB amps have an efficiency of around 50%. B class amps (also in
drivers) perhaps can raise it to 70%. 40% less input current and 55% less
dissipation, all at excellent IMD. All for nothing, oops, for lots of
programming if DSP is powerful enough.

Perhaps in 10 years nearly all new rigs will have predistortion implemented. 

Probably K3/KX3 do not have powerful enough DSP to do it. For example, the
biggest limit in KX3 on SSB is speech processor that is currently just a
treble boost.  6db lost. The fact that it is not done means that it cannot
be done easily. 

Ignacy, NO9E





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