Very impressive indeed. Pre-distortion will hopefully be made available as a option for the K3 in the future.
That would be a superb option if it does become available.
What these results however do confirm is that pre-distortrion is worth implimenting and that it does work very well.
The work by N1JEZ also confirms that current LDMOS amplifiers do not have acceptable levels of IMD performance, especially at higher powers.
In my opinion based on the IMD data by N1JEZ they are inherently very dirty. I have not seen a working example
of a LDMOS amplifier that I would consider clean when compared against even a pair of 3-500's. I have studied the NXP datasheets for these devices
and have found that LDMOS devices like the BLF574 can produce excellent IMD performance. The BLF574 according to the data sheet at 200 watts of ouput and 1200ma of idle current is capable of -40dbc 3rd order IMD performance. I have not seen data for the higher order products but this figure is good.
I have been working on a homebrew LDMOS solid state amplifier for my K3 and have not decided what devices I will use in the design. I do have a MRF150/EB104 amplifier that works very well and it has very good IMD performance. I would like to try these LDMOS designs. I wont however waste effort on a marginally poor IMD PA. Homebrewing is a lot of effort and I cant see the point of spending dollars and time on any project when it does not meet acceptable technical standards like IMD performance..
I wonder when we will see pre-distortion in a commercial ham radio tranceiver outside of the experimental devlopments like HPSDR. Is Elecraft working
on a pre-distortion implimentation?
73
Craig
"With bias, 12V transistors are class B or AB, not C.
See
http://flarc.net/eme-info/PDF/N1JEZ-2.pdf.
Ignacy, NO9E"
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