[Elecraft] Re: Displaying the keying waveshape on Spectrogram.

[Guy Olinger, K2AV]

I think I may have connected with Michael's thinking. We will see.

"MP" refers to the Yaesu FT-1000MP, a notorious click generator when
unmodified. It is very popular among contesters and a frequent driver
for QRO setups and monster antennas, and largely the evil responsible
for the current crusade to clean up clicks. It is a bit of a paradox
that rigs with the features and performance to endear themselves to
contesters are also the ones whose even slightest clickiness will be
paraded in front of the world. If the K2 didn't have such a superb
receiver in it, we might not be having this discussion on this
reflector.

The first thing to discuss is what kind of keying bandwidth trace am I
trying to build up with this setup, and what does it represent.

What it does NOT: It does not represent power, either summed over time
or summed at a frequency.

Clicks are a very "peaky" phenomenon and if nothing else, cause
trouble by just the instantaneous voltage they deliver, cranking up
the fast attack, slow decay AGC's and pushing down the weak station on
frequency. Or, blowing out dits of weak signals using fast attack,
fast delay AGC. Not sure which is worse.

Also, if you think about how you hear them, it's not the average power
of the clicks that is so annoying, it's how LOUD they are, for their
very short life. Our ears respond instantly to clicks

Therefore, I am creating a curve that represents the highest SINGLE
peak voltages measured at a series of sampling points, OVER A PERIOD
OF TIME, with continuing CW keying of the transmitter, with a slowly
varying keying speed from 10 to 50 wpm. The desired graph is created
in Spectrogram by turning on the PEAK HOLD function.

This is important, THE CURVE REPRESENTS THE COLLECTION OF EACH
FREQUENCY SPOT'S MAXIMUM PEAK "CLICK" OVER TIME AND VARYING KEYING,
NOT ANY *ONE* INSTANTANEOUS OCCURRENCE, OR ANY SUM UNDER THE CURVE, OR
ANY SINGLE NOISE POWER MEASUREMENT.

The varying of the keying speed will deliver the peak signal to each
point on the curve sooner or later. As you vary the keying speed, you
can see the curve "FILL UP" until varying the keying speed does not
change the curve any more.

After some experimentation, the only thing that happens if you widen
the sample time is that details of spiky artifacts get spread out. A
curve created in this way does not get WORSE by widening the
bandwidth, it gets less defined. The MP has spikey artifacts related
to capacitors fully charging between words, and what appears to be a
very short interval of transmission when circuits are doing their
TX/RX mode changes. They are better defined with short sample
intervals.

The curve that is generated means that Spectrogram, at a given
frequency, at one time or another, at one keying speed or another, has
measured that peak power.

If this curve dips below the noise between +/- 250 Hz line, given a
certain transmitter power, path loss and ambient noise, then you can
say for sure that the person using the adjacent channels will not hear
key clicks. If in these circumstances the line goes above the noise
into the next channel, then they will hear something. If the line is
WELL ABOVE the noise in the adjacent channel(s), then there will be
serious interference.

This is not an argument over how to figure the noise power given
bandwidth.

It is about curving a collection of "how bad can it be" points about a
transmitted signal. If you can get that kind of power in a single
Spectrogram 3 Hz sample point, it is able to interfere.

The measurements on an unmodified MP are consistent with reports and
complaints, and can be seen WAY outside the +/- 250 Hz limits. It does
seem to fully represent the

What is more important, everyone who follows the setup will generate
the same curve on the same signal.

I'm not sure what a proper name would be for the curve, but something
like "broad situation maximum of instantaneous samples by frequency"
would do. Maybe it already has a name from elsewhere?

In any event, anyone with an SSB receiver, PC, sound card, and
Spectrogram can produce consistent curves. Even if it doesn't relate
to some preexisting engineering standard, just having it reproducible
by ordinary means will make it valuable.

73, Guy.

.....

From: "George, W5YR" <w5yr@att.net>

> Michael, with all respect, I think you need to review the mechanics
of FFT
> processing. What you propose as a mechanism for Spectrogram
operation would
> result in a single data point for the energy integrated over the
entire FFT
> bin width which you would set equal to the receiver bandwidth..
>
> I don't know your background in this area, but evidently either
there is
> some considerable confusion or I am not understanding what it is
that you
> are trying to convey.

......

> From: "Masleid, Michael A." <Michael.Masleid@ispat.com>

> Hello Guy,
>
> I seem to have caused some confusion about what I
> am worried about.

.....


> >What we did with the wide SSB RX filter was to try and take the
> >receiver OUT OF PLAY. For moderate cases we succeeded quite
accurately
> >at handing the problem uncluttered to Spectrogram. From there on
it's
> >just math in a CPU.
>
> And finally, where I start to have trouble:  Is it possible that
> two filters with the same bandwidth will not respond to clicks the
> same way?  When I designed filters to correct for signal dispersion
> I used a time reversed conjugate match to the signal dispersion.
> I think there was something called a R.A.K.E. filter that was
> similar.  The implication is that a filter can be built to
> accent or attenuate the click, and still have the same apparent
> bandwidth.  A good job for a DSP no doubt.
>
> 73, Michael, AB9GV