P3 Feature Request - Transmit sampling

[EricJ-2]

That clears up something that has bothered me on JT65. Many times
someone will complain about someone overdriving, but the signal appeared
to be OK to me. It happens frequently. Now I think the "complainer" is
probably receiving the station much more strongly than I am and it is
overdriving his JT65 software. The signal is weaker for me and my
software is not being overdriven. The transmitted signal is indeed clean.

Thanks for the insight.

Eric
KE6US

On 9/25/2013 9:13 AM, Sverre Holm (LA3ZA) wrote:

> 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.
>
>
>
>
> -----
> Sverre, LA3ZA
>
> K2 #2198, K3 #3391,
> LA3ZA Blog: http://la3za.blogspot.com,
> LA3ZA Unofficial Guide to K2 modifications: http://la3za.blogspot.com/p/la3za-unofficial-guide-to-elecraft-k2.html
> --
> View this message in context: http://elecraft.365791.n2.nabble.com/P3-Feature-Request-Transmit-sampling-tp7579177p7579228.html
> Sent from the Elecraft mailing list archive at Nabble.com.
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>

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[WB4SON]

Well nothing would put the issue to bed better than a nice printout of a P3
screen that was sampling the RF signal over a bandwidth of about 6KHz.
 That's why I would LOVE for Elecraft to continue developing the P3 and
expanding its capability.

I don't mind the report, and I take it seriously, but I'd rather be able to
prove to myself that I'm clean rather than have a buddy stay up late at
night to run tests on my behalf.

And the other thing, of course, is the assumption that the decoding
algorithm is perfect and doesn't make mistakes, nor that a 6 KHz wide
bandwidth can be decoded with no artifacts on a Flex-3K -- these seem to be
suspect to me as well.

With so many accusations of bad modulation on what is essentially a weak
signal mode during a sun-spot maximum, being able to be 100% sure you are
clean seems like a very worthwhile goal.

I continue to run 5 watts and enjoy JT65, JT9 and PSK31 very much.

73, Bob, WB4SON



On Wed, Sep 25, 2013 at 12:19 PM, Rick Bates <[hidden email]>wrote:

> If your neighbor tells you it's clean (and s/he knows how to look) then
> it's likely the other station at fault.  Noise blanking, noise reduction,
> poor RX audio (over)driving are huge issues that can make any reception
> look bad.
>
> Bottom line: don't sweat it if your local stations tell you you're clean.
>
> whiners >> /dev/null
>
> 73,
> Rick wa6nhc
>
> Tiny iPhone 5 keypad, typos are inevitable
>
> > On Sep 25, 2013, at 9:13 AM, "Sverre Holm (LA3ZA)" <[hidden email]>
> wrote:
> >
> > 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.
> >
> >
> >
> >
> >
> > -----
> > Sverre, LA3ZA
> >
> > K2 #2198, K3 #3391,
> > LA3ZA Blog: http://la3za.blogspot.com,
> > LA3ZA Unofficial Guide to K2 modifications:
> http://la3za.blogspot.com/p/la3za-unofficial-guide-to-elecraft-k2.html
> > --
> > View this message in context:
> http://elecraft.365791.n2.nabble.com/P3-Feature-Request-Transmit-sampling-tp7579177p7579228.html
> > Sent from the Elecraft mailing list archive at Nabble.com.
> > ______________________________________________________________
> > Elecraft mailing list
> > Home: http://mailman.qth.net/mailman/listinfo/elecraft
> > Help: http://mailman.qth.net/mmfaq.htm
> > Post: mailto:[hidden email]
> >
> > This list hosted by: http://www.qsl.net
> > Please help support this email list: http://www.qsl.net/donate.html
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>

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[WB4SON]

Yep, that is 100% correct.

If the station that is offended would simply reduce their RF gain control,
in most cases they will see the signal clean right up.  Then the real issue
is that they want to copy a weak signal that is in a chunk of spectrum that
is full of strong signals (most likely due to excellent propagation).
 Somehow they think it is their right to complain to folks to lower their
power.  Imagine doing that in a contest!!  ("Hey Mr Strong station, I can
work that weak guy 100 Hz away from you.  Would you please lower your
power?"  -- not that we might not wish it, but we would never say it over
the air)

So I try to avoid the flak by running 5 watts and making sure my signal is
clean.  A P3 that RF sampled would take care of the second part.  But even
5 watts can be "too much" -- I worked Australia on 30 meters with 0.5 watts
and received a signal report of -10.  That wasn't me, that was all
propagation.

73, Bob, WB4SON
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[Bill Frantz]

My normal technique with sound card modes (mostly PSK31) is to
look at the audio AtoD overload indicator in my software and
reduce the RF gain so it indicates no overload. This procedure
uses the minimum necessary gain through most of the radio/AtoD
etc, limiting local distortion products. It works very well.

Most of the time I still see band noise on the waterfall, so I'm
not missing any weak signals. Sometimes the band noise goes away
and I wish I had better dynamic range.

Cheers - Bill, AE6JV

On 9/25/13 at 10:21 AM, [hidden email] (Bob) wrote:

>If the station that is offended would simply reduce their RF gain control,
>in most cases they will see the signal clean right up.

---------------------------------------------------------------------------
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up the
408-356-8506       | intelligence.  There's a knob called
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[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)" <[hidden email]>
To: [hidden email]
Subject: Re: [Elecraft] P3 Feature Request - Transmit sampling
Message-ID: <[hidden email]>
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
[hidden email]
"Kits made by KL7UW"

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