DC to DC is used in video and RF frequency, over 50 years I know of,all the
time to get away from 60hz and other design nonlinearities.
Retired NIST DC to 18GHz lab tech
AB7CE Roy
-----Original Message-----
From: Dr. William J. Schmidt
Sent: Monday, September 14, 2020 10:05 AM
To: elecraft@mailman.qth.net
Subject: Re: [Elecraft] Why predistortion ?
Always tradeoffs to be made. Boosting 12V volts to 50V means some sort of
converter that can add its own distortion products, plus expense and
additional complexity (read that "reliability") and efficiency. There's no
free lunch here.
Dr. William J. Schmidt - K9HZ J68HZ
email: b...@wjschmidt.com
-----Original Message-----
From: elecraft-boun...@mailman.qth.net
[mailto:elecraft-boun...@mailman.qth.net] On Behalf Of Charlie T
Sent: Monday, September 14, 2020 6:30 AM
To: elecraft@mailman.qth.net
Subject: Re: [Elecraft] Why predistortion ?
Maybe I'm missing something here, but it would seem to me that if an FET
linear amplifier running from 50 V or higher is considerably cleaner than
one running from 12 V, that, for a high end rig, a simple step-up switching
supply could solve the problem. But, that obviously adds to the cost so it
IS somewhat of a conundrum.
However, implementing the pre-distortion function IS probably a better
long-term solution.
73, Charlie k3ICH
-----Original Message-----
From: elecraft-boun...@mailman.qth.net <elecraft-boun...@mailman.qth.net> On
Behalf Of David Gilbert
Sent: Monday, September 14, 2020 12:43 AM
To: Elecraft Reflector <elecraft@mailman.qth.net>
Subject: Re: [Elecraft] Why predistortion ?
Of course, but that's a conscious choice by Elecraft and it does not result
in the "cleanest, purest signals around." I give Elecraft tons of credit
for the other measures they have take to produce good signals, which is why
I own and will keep my upgraded K3 probably forever, but K8JHR simply was
incorrect in his comment and it makes a difference when considering the
expanding focus by folks like Sherwood and others to clean up the bands.
When it comes to IMD, Elecraft is not one of the better players. The fact
that that's by choice doesn't change anything. I suspect that 95+% of K3
rigs are used in portable/emergency situations less than 5% of the time.
73,
Dave AB7E
On 9/13/2020 7:14 PM, Wayne Burdick wrote:
12 volts is a severe constraint for MOSFET PAs. But, like a lot of other
manufacturers, we accept this constraint so the equipment can be used in a
wide variety of portable/emergency power situations. As a result we have IMD
numbers in exactly the same range as other products that are subject to this
constraint.
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.
73,
Wayne
N6KR
On Sep 13, 2020, at 6:50 PM, David Gilbert <ab7e...@gmail.com> wrote:
I don't know where you got the idea that the K-Line produces the cleanest
signals. As several people have pointed out, because of the 12 volt finals
the transmit IMD performance of the existing K-line is relatively poor.
Dave AB7E
On 9/13/2020 2:32 PM, JR wrote:
Why are so many ops obsessed with predistortion?
The Elecraft K-Line already produces some of the cleanest, purest
transmit signals around. Do we need predistortion ? If so, why, and how
much better is it than what we already have? Should I wait to buy a new rig
until that is available?
Thanks and Happy Trails to all. K8JHR
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