[Elecraft] P3 Feature Request - Transmit sampling

[Edward R Cole]

This moving to OT but interesting to a long-term JT65 user like me.

JT65 was designed for weak-signal communication, so the situations on 
HF where strong signals are received might be a problem.  I would 
like to hear what Joe Taylor (K1JT) would say regarding this.  I have 
not used JT9 or many of the variants of JT65; no use of it on HF.  So 
have no experience with strong JT signals.  On eme a strong signal is 
-15 or higher.

You may be correct about JT9 coding.

With the K3 or KX3 the important point is to set up modulation the 
proper way using the ALC meter (four dashes with the fifth 
flickering).  I really like the way Elecraft makes it simple to set 
up digital mode levels correctly and easily.  Previous use of JT44 
and then JT65 was with a FT-847 and one had to just find the point 
where level started compression and back of a tad.  The DATA jack on 
the FT-847 was nice since Rx audio was low-level at constant 
amplitude and modulation was separated from the mic.  But I think one 
still had to adjust mic gain and turn off mic compression for data 
modes (Not a preset mode like on Elecraft radios).

73, Ed - KL7UW
---------------
From: "Sverre Holm (LA3ZA)" <LA3ZA at nrrl.no>
To: elecraft at mailman.qth.net
Subject: Re: [Elecraft] P3 Feature Request - Transmit sampling
Message-ID: <1380125612061-7579228.post at n2.nabble.com>
Content-Type: text/plain; charset=us-ascii

As your post indicates, the splattering of JT65 signals has most likely
nothing to do with your transmitter and setup. It is more likely to be due
to the specifics of the JT65 display/decoding algorithm than anything else.
I have done spectral estimation for some 30+ years and it reminds me very
much of the phenomenon called sidelobe leakage. I have commented on that in
my blog:
Overmodulated JT65 on HF?
<http://la3za.blogspot.no/2013/04/overmodulated-jt65-on-hf.html>

WB4SON wrote
 > Yesterday I received an email from a ham a few thousand miles away asking
 > me to clean up my signal -- I was running JT65 at the time, and he saw my
 > signal decode on his rig in a half-dozen spots across the waterfall.
 > ....
 > Later that night a nearby ham was nice
 > enough to run a spectral analysis on my signal and found it looked clean
 > as
 > well.

73, Ed - KL7UW
http://www.kl7uw.com
dubususa at gmail.com
"Kits made by KL7UW"