Why predistortion ?

[JHRichards]

        Mr. Wayne said --  "On the other hand, our transceivers are best
        in class in terms of transmitted keying bandwidth.  See paper by
        K9YC for example.  Perhaps that's what JR was thinking of."

        ------------------------------------

YES,  that is EXACTLY what I was thinking of!   Parenthetically, K9YC
created that particular document specifically in response to my request
on another reflector for quantification relative to unsubstantiated
claims contradicting what ARRL Lab guru Bob Alison, WB1GCM, told me.   I
believe it is the only piece that compiles the available data in a
single document.

THANK YOU for the enlightening reply, Mr. Wayne - I appreciate the leg
up.  One can learn a lot just by asking questions.   K8JHR
__________________________________



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[Jim Brown-10]

On 9/14/2020 5:21 PM, JR wrote:
> Parenthetically, K9YC created that particular document specifically in
> response to my request on another reflector for quantification relative
> to unsubstantiated claims contradicting what ARRL Lab guru Bob Alison,
> WB1GCM, told me.

That piece I compiled came from Bob's raw data. In essence, I plotted
data for that select list of products on the same graph, with the scale
large enough to compare each product. The plots were of running averages
of adjacent data points to smooth it, again to make it more readable.

73, Jim K9YC




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[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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