Hi Dave, Joe, and Jim
The GMSK to AM distortion across any 50 Hz bandwidth of a K3 filter would seem
to be minor. With an FT8 symbol rate of 6.25 symbols per second, would that not
create some relatively weak 6.25 Hz sidebands plus a bit of mush around those
lines due to the pseudorandom
Doppler caused "spreading" is readily identified ... the spreading is
generally in one direction (because airport "patterns" run in one
direction) and often manifests as a second signal offset by 60-80 Hz
(which can be independently decoded). IMD is generally in both
directions and can not be
On 7/23/2023 9:49 AM, Andy Durbin wrote:
It is my belief that many of the wide FT8 signals seen on 6 m FT8 are caused by
Doppler shifted aircraft reflections. It's very common here in the Phoenix
metro area and does not imply that the transmitted signal was in any way
abnormal.
YES! It's
"Clean FT8 spectra is badly needed, especially in metro areas at 10 meters and
above, where many poor quality FT8 signals abound and wipe out many of the
weaker stations that other stations are trying to receive. Yes, there are
suggestions that folks in the same area all transmit at the same
Hello Mike,
Thanks for sharing your data!! Help me understand something you said...
Are you saying that at 2 bars, (for your K4), all spurious signals, are
at least 80 dB down from carrier, while at 5 bars, all spurious signals
are running around 50 or 60 dB down from carrier?
73, and
Oh my goodness!
What Don, W3FPR wrote is 100% correct!
Whomever K3 user told you to EVER use the output control other than MAX at ALL
TIMES needs to go back to learning. They are NOT helping you. (NK7I)
I'd go back to what Elecraft says in their manual. (K9YC)
Again, READ THE K3 OWNERS
That the K3 and K4 are clean transmitters (for a 12V final) is awesome for
everyone on the air. Elecraft sets the bar again.
But the highly popular JT modes are not the only audio based digital modes used
these days. Others are more complex than one continuous phase shifted tone.
With that
I have been running tests on K3s and K4s to understand the conditions needed
to transmit clean FT8 signals. I have previously shared some of my findings
with Pete N4ZR and a couple of other folks. Their feedback has been very
valuable.
Joe Taylor, K1JT has shown the spectral purity of the FT4
"It will remain as clean as the audio, up to the point the ALC begins to kick
in; then it goes bad like any other radio. That’s the fault of ALC, not the
radio."
What goes bad? Nothing goes bad for a Kenwood TS-590S when drive level moves
into the ALC closed loop control range. Remember
Are you sure the "technically-qualified local ham" was not running his
tests in SSB instead of DATA A? There are more than a few "technically-
qualified" individuals who insist on using SSB instead of DATA_A with
WSJTX and that makes all the difference in the ALC display.
Again, READ THE K3
Pete,
I would suspect that the local ham didn’t account for you overdriving his
receiver (or test set) which would explain why an underdriven signal appeared
cleaner (no overload). Had he attenuated your 4 bar signal, it would have been
clean, I’m 100% certain.
A full audio supplied (just shy
Sorry, but I would want to see live spectrum displays of my own rig with
a known hardware setup instead of images of some other K3 with unknown
K3 settings and unknown test setup. Hundreds of us have been following
the just barely flickering 5 bar rule with excellent performance.
You know
I recommend finding someone with a P3 or other spectrum display and trying this
on *your* K3 rather than looking at pictures of “a K3”. Running with
insufficient audio drive, which is what you are doing, has known problems,
which you are experiencing.
I would be glad to do it with my KX3 and
OK guys - rather than reply individually, let me try to pull everything
together in one message.
In a previous effort at FT8 I followed the standard advice to set the
power slider in WSJT-X (on the lower RIGHT side) so that my K-3 showed 4
bars on the ALC meter, just below the threshold for
Hi Jim,
Maybe you’d feel better knowing that with WSJT-X at max; I had always adjusted
the OS driver level plus the rig levels, starting mid range on both. And from
midway, find the right blend to get the level to be proper with neither control
at (or near) max so nobody shouts and no one
On 7/20/2023 2:47 PM, Rick NK7I wrote:
s said MANY times, set the WSJT-X output to MAX, then IGNORE IT.
Hi Rick,
This is the only part of your excellent advice that I disagree with. The
reason is that the analog stages of computer gear tend to be poor, and
start generating increased
On 7/20/2023 2:16 PM, Pete Smith N4ZR wrote:
I've recently started operating FT8, and on advice from other K3 users,
have been adjusting the power slider in WSJT-X to a level just short of
or just into the first flickers of ALC. I did this because I was
advised that setting the slider for 4
, 20 Jul 2023 17:16:47 -0400
From: Pete Smith N4ZR mailto:pete.n...@gmail.com> >
To: Elecraft List mailto:elecraft@mailman.qth.net> >
Subject: [Elecraft] K3 Power-hunting on FT8
Message-ID: mailto:caff765b-c334-0990-072f-a2e7f1632...@gmail.com> >
Content-Type: text/plain; cha
Whomever K3 user told you to EVER use the output control other than MAX at ALL
TIMES needs to go back to learning. They are NOT helping you.
The WSJT-X output control is an AUDIO control, not an RF output control.
On any rig made since 1985, one wants to adjust the RF for RF and the audio for
Pete,
Set the audio level to make the first 4 bars of the ALC meter solid with
the 5th bar just flickering.
The K3 ALC onset is at the 5th bar, the bars below it are an aid to
adjusting the audio properly for digital modes.
Your advice from "other K3 users" is not correct. ALC starts at the
Pete:
The first 4 bars on the K3 ALC are just an audio level indication [i.e.
VU meter]. ALC action starts at the 5th bar, which you want to be just
flickering. Unless you have 4 solid bars, the K3 will keep trying to
adjust the TX gain to achieve the selected output power and it may not
By “first flickers of ALC” do you mean one bar flickering? If so, that will
cause power hunting.
Not sure who advised against setting it at the 4th bar, but that was probably
bad advice. That sounds like advice for non-Elecraft transmitters. I recommend
following the setup instructions on
Hi Peter,
Setting the ALC for FT8 is different than other transceivers due to the way the
K3 adjusts power.
You should adjust the slider to give four solid bars and the fifth flickering.
You find the outputvwull be ver stable then.
See you on the bands!
—-Paul AK1P
Sent from my iPhone
>
I've recently started operating FT8, and on advice from other K3 users,
have been adjusting the power slider in WSJT-X to a level just short of
or just into the first flickers of ALC. I did this because I was
advised that setting the slider for 4 or 5 bars of ALC generated junk in
the FT8
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