Topband: Rig Comparisons

[James Wolf]

Rick,

I can see where the approach in the paper could be a solution to existing
transmitting systems.  Unless the semantics of pre-distortion have eluded
me, a closed loop which is integral to the design of the complete amplifier
is a much better solution; as it is hands-off.   In every case, whether or
not it is a calibrated lookup table or an active correction method, a sample
of the output is needed (at some point) to pre-distort the input to the
amplifier stages as much as possible.  Simple negative feedback that has
been used in tube and transistor circuits is really not much more than a
gain controller to stabilize the amplifier stage(s).   It doesn't know how
the input waveform has to be 'shaped' to cause a less undistorted output
signal.

Jim - KR9U


~~~~~~~
We can measure the characteristics of the amplifier by using the receiver of
our SDR to receive the
amplifier's output and then comparing the signals going into and coming out
of the amplifier. Note,
however, that receiving the amplifier's output signal requires a feedback
path to be established from
the amplifier output to the receiver input during the time that we are
transmitting. Clearly this must be
done with a directional coupler/attenuator or sampler/attenuator so as to
deliver ONLY the required
amount of power back into the receiver input.
~~~~~~~
-----Original Message-----
From: Richard (Rick) Karlquist [mailto:richard at karlquist.com] 
Sent: Saturday, August 02, 2014 11:11 PM
To: jbwolf at comcast.net; topband at contesting.com
Subject: Re: Topband: Rig Comparisons



On 8/2/2014 7:53 PM, James Wolf wrote:
> Rick,
>
> Is the report public? Do you have a link to it?
>
> Jim - KR9U
>

This is the report I read; it was at the top of the Google search results:

http://www.wavenode.com/PureSignal.pdf

Maybe I didn't read the right paper.
Like I said,  this paper is clearly
not on the same page with what Paul C. said.
Paul, can you point us to the correct paper to read?

Rick N6RK