[Elecraft] Why predistortion ?

[Ignacy]

Many factors influence how wide the signal is in SSB, not just IMD3 numbers.
These are:

1. Quality of ALC. Here K3 is excellent. FTxxxx in class A poor. 
2. Overdriving the amp. Operators choice or ignorance. 
3. Transmit bandwidth. Could be 300-2400 in contests. No adjustment in K3
except by crude EQ. 
4. Amount of speech processing. 
5. Equalization. 

Following W2XJ, the future is in the amp containing the complete TX stream.
Perhaps only 3 stages, with DAC following by LNA directly driving the LDMOS 
finals, with bandpass and final filters.  All what K4 (or K5 ) does, it to
send relevant info to TX via Ethernet. Even better, have all in one box
(K5_1500X).  

Probably the hardware cost is minimal. Nearly all the cost is in software
dev't.

Ignacy, NO9E



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