[Elecraft] KRX3 vs APF on weak signals ??

Guy Olinger K2AV olinger at bellsouth.net
Wed Jul 13 05:52:51 EDT 2011


You insist on making this an either/or kind of choice, and it simply
is not.  APF does not make a result in your brain, it simply listens
to slower CW with a very narrow bandwidth. It seems to have times when
it will pull something out of noise, and other times not, by use of
the narrowness.

Diversity does not narrow what you hear.  The randomness of noise
causes it to spread around the audio "compass" while discrete signals
will appear to come from a single direction, and signals going through
fades will do a "rotation" at the bottom without actually losing copy.
 The spreading around of the noise is sometimes worth 10/15 dB of
"separation" with whisper level signals in the clear, and undetectable
in the monophonic, even with APF.  With different kinds of noise, only
the APF seems to work to pull out a signal.

This and APF are not an either/or thing.  I use one or the other, and
rarely, both at the same time.

If you can get a chance to listen to a K3 on diversity, you will
understand.  IF for some very silly reason I was forced to chose
between APF and diversity, I would chose diversity, because of all the
other uses of the excellent second RX.

Go hear one.

73, Guy.

On Tue, Jul 12, 2011 at 10:39 PM, callen1155 <callen1155 at yahoo.com> wrote:
> Thanks for the responses but I'm at a loss as to why the question is
> confusing. I'm trying to determine the most efficient method to hear
> weak/fading cw signals.
>
> I have read on here many times where folks brag on the 2nd receivers'
> ability to overcome fading band conditions via diversity receive using
> complementing antennas. I have read and experienced the benefit of APF under
> those same band conditions as well.
>
> I understand diversity receive and APF go about it two totally different
> ways but the end result is an improved ability to hear weak/fading signals.
>
> My question is simply, under weak/fading band conditions when you're
> straining to copy the cw sig (assuming you have both APF and diversity
> receive to choose from), which would you choose to improve your copy and
> make the contact?
>
> thanks again.
> chuck
>
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