On 2020-09-14 7:29 AM, Charlie T wrote:
>
However, implementing the pre-distortion function IS probably a
better long-term solution.
Pre-distortion on a 12V rig only hides the problem. Any "home
station" rig should have 28/50 V finals *and* then one can make
it even cleaner with pre-distortion. If necessary, use 50V
capable finals at 50W maximum output for 12V operation and
150-200 W output when a 48V supply is available.
73,
... Joe, W4TV
On 2020-09-14 7:29 AM, Charlie T wrote:
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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