Interpretation of P3 display

[Harold V]

I have a question for the group regarding interpretation of the P3 display of
SSB signals.

Primarily I use it to spot stations on quiet bands or spot openings on busy
bands.  But I am trying to gain a better understanding of what it is showing me
regarding the quality of signals as well.

I have my P3 set up to show the band width as a column and the span set to +/-
25.  I have noticed that most SSB signals will remain within the bounds of the
column.  However, some SSB signals will exceed the width of the column and will
resemble a pyramid, occupying several kilohertz above and below the column on
voice peaks.  The proximity of the station does not appear to matter as these
observations apply to distant stations as well as local stations.

Is this what is known as "splatter"?  Is the station overdriving their
transmitter or linear?  Is their ALC or compression too high?  Is the frequency
response of their microphone too wide?

A good friend of mine has a K3/P3 and we have discussed this at length and come
to the conclusion that we really don't understand what we are seeing.  Anyone on
the list have comments as to what they have observed or an explanation of what
we are seeing?

Any relevant comments would be appreciated.

Thanks
Van
K0HCV
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[Jim Brown-10]

On 6/8/2012 11:45 AM, Harold V wrote:

> Is this what is known as "splatter"?

The triangular shape is most likely phase noise.

> Is the station overdriving their transmitter or linear?

The most likely causes are phase noise produced by inferior transceiver
designs, and distortion products in transmitters and power amps.

>   Is their ALC or compression too high?

That can also be a cause, and also overdriving audio.  These products
would vary in strength with modulation, and most prominent on audio peaks.

>   Is the frequency response of their microphone too wide?

No -- transmitted bandwidth is limited by the transmitting filters in
the transceiver. Virtually all mics have response from at least 50 Hz to
at least 10 kHz, although the degree of uniformity can vary widely from
one mic to another.

73, Jim K9YC
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[vk4tux]

Are you using the waterfall ? Seems like you are just using the scope, with
no combo waterfall display beneath.
The waterfall shows splatter very well.

Adrian ... vk4tux

-----Original Message-----
From: [hidden email]
[mailto:[hidden email]] On Behalf Of Harold V
Sent: Saturday, 9 June 2012 4:46 AM
To: [hidden email]
Subject: [Elecraft] Interpretation of P3 display

I have a question for the group regarding interpretation of the P3 display
of SSB signals.

Primarily I use it to spot stations on quiet bands or spot openings on busy
bands.  But I am trying to gain a better understanding of what it is showing
me regarding the quality of signals as well.

I have my P3 set up to show the band width as a column and the span set to
+/- 25.  I have noticed that most SSB signals will remain within the bounds
of the column.  However, some SSB signals will exceed the width of the
column and will resemble a pyramid, occupying several kilohertz above and
below the column on voice peaks.  The proximity of the station does not
appear to matter as these observations apply to distant stations as well as
local stations.

Is this what is known as "splatter"?  Is the station overdriving their
transmitter or linear?  Is their ALC or compression too high?  Is the
frequency response of their microphone too wide?

A good friend of mine has a K3/P3 and we have discussed this at length and
come to the conclusion that we really don't understand what we are seeing.
Anyone on the list have comments as to what they have observed or an
explanation of what we are seeing?

Any relevant comments would be appreciated.

Thanks
Van
K0HCV
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[k6dgw]

On 6/8/2012 11:45 AM, Harold V wrote:
> I have a question for the group regarding interpretation of the P3 display of
> SSB signals.
>
> Primarily I use it to spot stations on quiet bands or spot openings on busy
> bands.  But I am trying to gain a better understanding of what it is showing me
> regarding the quality of signals as well.

I run mine at spans of 20 or 40 KHz [I have the PF keys set for those]
when operating in contests or when I want to see the immediate band
around me.  I use fixed-track all the time, so sometimes it's not "all
around me," just on one side.  If I want to look at someone's signal
spectrum, I go to a span of 6.  If he's really wide, I'll look at it at
a span of 10 KHz.

> Is this what is known as "splatter"?  Is the station overdriving their
> transmitter or linear?  Is their ALC or compression too high?  Is the frequency
> response of their microphone too wide?

OK Van, multiple questions.  What most folks call splatter is caused by
driving the last amplifier stage into saturation [i.e. it can't produce
any more power so it clips off the peaks].  It doesn't really involve
compression, they're just driving their amplifier into saturation, it
clips the peaks [a very non-linear occurrence], and all sorts of IMD is
generated around their signal.  The cure is, "Don't drive your amplifier
into saturation."  This is sometimes called flat-topping.

Another problem could be phase noise.  This is generated inherently in
the transmitter part of your radio, and is essentially unwanted random
FM modulation of your signal caused by jitter in the frequency.  Phase
noise on a signal will be essentially independent of the strength of the
signal, within reason, although the guy down the block with 1.5 KW and
lots of phase noise can easily take out the entire band for you when he
taps his paddle.
>
> A good friend of mine has a K3/P3 and we have discussed this at length and come
> to the conclusion that we really don't understand what we are seeing.  Anyone on
> the list have comments as to what they have observed or an explanation of what
> we are seeing?

There are a whole lot of other causes.  Getting an amplifier and
saturating the core in your balun can wreak havoc on the ham bands, and
on your neighbor's TV's if they're receiving over the air.  Same effect
as driving your amplifier to saturation.

Highly compressed audio can lead to unintelligibility on SSB.  It tends
to be a bit wider, but the real problem is it totally fills the
bandwidth with no dynamic range, something we depend on in our heads to
understand speech.  ESSB signals will be broader, as will AM.

I've been watching WWV on 10 MHz.  I'm working on a project for my wife
and I need to get the little PIC to keep time reasonably well.  At 4 KHz
span, I'm surprised by the spectrum.  It *IS* WWV, I'm sure there's
nothing wrong, but I still can't explain what I see.

Your P3 opens a whole different view of the radio spectrum.  It's worth
exploring.

73,

Fred K6DGW
- Northern California Contest Club
- CU in the 2012 Cal QSO Party 6-7 Oct 2012
- www.cqp.org

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[Geoffrey Mackenzie-Kennedy-3]

Fred and Van,

Some comment follows.

On June 09, 2012 at 7:03 AM, Fred Jensen K6DGW wrote:

<snip>


> OK Van, multiple questions.  What most folks call splatter is caused by
> driving the last amplifier stage into saturation [i.e. it can't produce
> any more power so it clips off the peaks].  It doesn't really involve
> compression, they're just driving their amplifier into saturation, it
> clips the peaks [a very non-linear occurrence], and all sorts of IMD is
> generated around their signal.  The cure is, "Don't drive your amplifier
> into saturation."  This is sometimes called flat-topping.

Fred, although IMHO your advice is sound, please don't forget that prime law
of physics which states that "Garbage in will result in Garbage out".
Overdriving any amplifier in an exciter used to drive an amplifier (with
some exeptions e.g. most pre-filter amplifiers) will result in splatter
being transmitted, even if the final amplifier is squeaky clean and linear
at any output power level.

My intention for saying this is that the typical ALC arrangement is often
incorrectly used as a means to control the level of power output from the
exciter and/or amplifier to some chosen level, rather than as a protective
device, and can be responsible for splatter.

Van, the reason why a typical ALC can be responsible for splatter is because
these ALC systems sample the output of an amplifier and/or exciter, and due
to time delays cannot "throttle back" the drive power immediately. As a
result a burst of excess drive power can be produced, especially during
voice peaks, which can result in some amplifier(s) in the transmitter chain
being overdriven and creating splatter. There are types of ALC system used
which do not create this problem, but that's another subject.

73,

Geoff
LX2AO











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[Jim Brown-10]

On 6/9/2012 5:14 AM, Geoffrey Mackenzie-Kennedy wrote:
> the reason why a typical ALC can be responsible for splatter is because
> these ALC systems sample the output of an amplifier and/or exciter, and due
> to time delays cannot "throttle back" the drive power immediately.

The ONLY proper ways to set power output are 1) to turn down the
transceiver's output power by turning down the power control on the
transceiver; or 2) using a resistive attenuator (voltage divider)
between the transceiver and the amplifier.  W8JI, who has designed a lot
of power amps, and, as part of that design work, has studied the
behaviour of lots of ham transceivers, has written an excellent and
detailed tutorial on this matter, and on how some ham transceiver ALC
systems badly misbehave, and NEED to use option 2.  The K3 (and the
FT1000MP)  do not have this problem, and work fine with option 1.

ALC from the power amp to the transceiver should NEVER be used to set
transmit power, for the reasons you've noted. It is provided for on most
ham products because many hams think they need it.  If used at all,
transceiver output level should be set so that ALC ONLY protects the
amplifier by backing off the drive when something in the antenna system
breaks, creating a load that the power amp is unhappy with.

Note also that this advice is NOT new, and applies equally to old power
amps.  I first saw this advice in the manual for my 35 year old Ten Tec
power amps.

73, Jim K9YC
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[vk4tux]

What have these last few posts got to do with interpretation of the P3
display?

-----Original Message-----
From: [hidden email]
[mailto:[hidden email]] On Behalf Of Geoffrey
Mackenzie-Kennedy
Sent: Saturday, 9 June 2012 10:14 PM
To: Elecraft Discussion List
Subject: Re: [Elecraft] Interpretation of P3 display

Fred and Van,

Some comment follows.

On June 09, 2012 at 7:03 AM, Fred Jensen K6DGW wrote:

<snip>


> OK Van, multiple questions.  What most folks call splatter is caused
> by driving the last amplifier stage into saturation [i.e. it can't
> produce any more power so it clips off the peaks].  It doesn't really
> involve compression, they're just driving their amplifier into
> saturation, it clips the peaks [a very non-linear occurrence], and all
> sorts of IMD is generated around their signal.  The cure is, "Don't
> drive your amplifier into saturation."  This is sometimes called
flat-topping.

Fred, although IMHO your advice is sound, please don't forget that prime law
of physics which states that "Garbage in will result in Garbage out".
Overdriving any amplifier in an exciter used to drive an amplifier (with
some exeptions e.g. most pre-filter amplifiers) will result in splatter
being transmitted, even if the final amplifier is squeaky clean and linear
at any output power level.

My intention for saying this is that the typical ALC arrangement is often
incorrectly used as a means to control the level of power output from the
exciter and/or amplifier to some chosen level, rather than as a protective
device, and can be responsible for splatter.

Van, the reason why a typical ALC can be responsible for splatter is because
these ALC systems sample the output of an amplifier and/or exciter, and due
to time delays cannot "throttle back" the drive power immediately. As a
result a burst of excess drive power can be produced, especially during
voice peaks, which can result in some amplifier(s) in the transmitter chain
being overdriven and creating splatter. There are types of ALC system used
which do not create this problem, but that's another subject.

73,

Geoff
LX2AO











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[Geoffrey Mackenzie-Kennedy-3]

Van did ask , and I quote:

"Is this what is known as "splatter"?  Is the station overdriving their
transmitter or linear?  Is their ALC or compression too high?  Is the
frequency
response of their microphone too wide?"

73,
Geoff
LX2AO



On June 09, 2012 at 4:19 PM, "Adrian" <[hidden email]> wrote:


> What have these last few posts got to do with interpretation of the P3
> display?

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[Ken G Kopp]

The replies directly answer the initial poster's question about
the cause of what his P3's display was likely showing.

73!

Ken - K0PP
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[David Gilbert]

Anything that represents a transmit non-linearity can cause splatter,
and a very quick change in gain represents a non-linearity.

My ICOM 756Pro was one of those offenders that used an internal ALC to
set the power level.  The internal delay in the ALC caused nasty power
spikes at the beginning of transmissions that kept tripping the
overdrive protection on my TenTec ALS-500 solid state amp.  It was a
stupid system and I don't know if ICOM ever addressed it with their
later rigs.  Amplifiers that use screen grid tubes like the GU-74B also
do not those fast leading edge power spikes, making me grateful for the
way the K3 handles things.

73,
Dave   AB7E


On 6/9/2012 7:03 AM, Jim Brown wrote:

> On 6/9/2012 5:14 AM, Geoffrey Mackenzie-Kennedy wrote:
>> the reason why a typical ALC can be responsible for splatter is because
>> these ALC systems sample the output of an amplifier and/or exciter, and due
>> to time delays cannot "throttle back" the drive power immediately.
> The ONLY proper ways to set power output are 1) to turn down the
> transceiver's output power by turning down the power control on the
> transceiver; or 2) using a resistive attenuator (voltage divider)
> between the transceiver and the amplifier.  W8JI, who has designed a lot
> of power amps, and, as part of that design work, has studied the
> behaviour of lots of ham transceivers, has written an excellent and
> detailed tutorial on this matter, and on how some ham transceiver ALC
> systems badly misbehave, and NEED to use option 2.  The K3 (and the
> FT1000MP)  do not have this problem, and work fine with option 1.
>
>
> 73, Jim K9YC
>

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[Roy Morris-6]

David, what are you saying?  Do the GU74bs dislike or do they tolerate the
spike?  You left out an important word in your previous statement.  Thanks,
Roy  W4WFB

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[David Gilbert]

Sorry ...

Amplifiers with a pair of GU-74Bs typically want to be driven at less
than 50 watts for full legal power, and from what I understand (I'm not
an expert) their screen grids can be damaged with excess drive levels.  
Those amplifiers almost always have pretty sophisticated drive limiting
and protection circuitry, but repetitive spikes of overdrive (like from
an ALC controlled transceiver) could still be harmful to them ... at
least as I understand things.  Maybe somebody who truly knows can
clarify here.

In any case, those spikes of power above 50 watts (like from my old
756Pro) certainly could push the amplifier into flat topping and create
pulses of splatter.

73,
Dave   AB7E



On 6/9/2012 12:41 PM, Roy Morris wrote:
> David, what are you saying?  Do the GU74bs dislike or do they tolerate the
> spike?  You left out an important word in your previous statement.  Thanks,
> Roy  W4WFB
>
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[Tom Azlin N4ZPT-2]

Hi Harold,

On 6/8/2012 2:45 PM, Harold V wrote:

> I have a question for the group regarding interpretation of the P3 display of
> SSB signals.
>
> Primarily I use it to spot stations on quiet bands or spot openings on busy
> bands.  But I am trying to gain a better understanding of what it is showing me
> regarding the quality of signals as well.
>
> I have my P3 set up to show the band width as a column and the span set to +/-
> 25.  I have noticed that most SSB signals will remain within the bounds of the
> column.  However, some SSB signals will exceed the width of the column and will
> resemble a pyramid, occupying several kilohertz above and below the column on
> voice peaks.  The proximity of the station does not appear to matter as these
> observations apply to distant stations as well as local stations.
>
> Is this what is known as "splatter"?  Is the station overdriving their
> transmitter or linear?  Is their ALC or compression too high?  Is the frequency
> response of their microphone too wide?

Send a captured snapshot using the P3 utility. On the water fall I see
stations there their signal goes well past other signals.

Yes, I see similar and I would call it splatter.  Especially when it is
clear other stations are not doing this. Over driving something past
their SSB filters. On a local net where the are mixtures of vintage and
modern the vintage ones ( on this net) tend to be much broader and for
sure they are not over driving.

73, tom n4zpt

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[Val-12]

Of course it dislikes the spike as every other tube or transistor does.
However some of the GU74B amplifiers have sophisticated protection circuits
that every spike trips , while an unprotected tube amplifier wouldn't notice
it.

73, Val LZ1VB


> David, what are you saying?  Do the GU74bs dislike or do they tolerate the
> spike?  You left out an important word in your previous statement.
> Thanks,
> Roy  W4WFB

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[Guy, K2AV]

Gu74B, aka 4CX800A, is a tetrode, a pair used in Alpha manual tune amps
since the 91B, replaced recently with 4CX1000A's in the Alpha 8410.  The
4CX1000A's have the same protection needs.  The same protection needs exist
for the 4CX150A's in my ancient Tokyo Hy-Power HL-1K, but it's not there
and if you spike 'em, you can blow 'em.

*** Spikes are bad with tetrodes. ***  Need a minor bit of theory to
explain.  Oversimplifying  just a little...

Some amps can tolerate spikes, but nearly all screen grid tubes commonly
used in ham amplifiers depend on running with VERY small control grid
current, single figure milliamps. The control grids for these tubes run
with negative bias that exceeds the normal positive going peak RF drive
signal value.  Therefore any level of signal whose positive peak exceeds
the negative grid bias will go into non-linearity and excessive current.
 Alpha's and other amps consider this a fault condition in and of itself,
REGARDLESS OF DURATION.  This fall-off-the-cliff point in drive voltage is
most UN-like the zero-bias triodes in grounded grid amps which always have
significant grid current under normal drive and loading, and get to
over-drive in a far more "gradual" way as you increase drive power.

SINCE most ham amp tetrode transmitting tubes are designed to work in that
no-grid-current zone (look up AB1 in the tube operation section of the ARRL
handbook), they do NOT have the huge clunky grid structure of a 3CX1200A7
or 3-1000Z.  Tetrodes have very fine control grid wires, JUST BECAUSE they
supposedly don't need to carry anything except very low current.  There are
some very useful engineering advantages to these fine wires which I won't
get into.

Amps with Gu74B's and like tubes in a grounded cathode configuration (as in
the 8410) will require a 50 ohm power absorbing circuit (aka swamping)  in
the input circuitry, in parallel with the control grids, so that the
transceiver does not see the very high natural resistance of the biased
control grids themselves.  Normal drive to full power output in these amps
does NOT require drive voltage that exceeds the grid voltage.  A pair of
4CX1000A with drive power right at the grid bias is hardly legal in this
country.  Pair of GU74B also illegal this way, though not so blantant.

If you look at the front panel of an 8410, you will note there is no way to
measure grid current.  Just a green light and a red light.  The green light
just barely flickers under correct operation.  Solid green means you are
pushing it a little, and there is a certain amount of capacitive current in
the grid.  Red means you are creeping up to the fault level and you need to
back off.  All of these conditions are tiny single digit milliampere
currents that can occur without going past the control grid bias level.

The full scale value for grid current on my HL-1K is THREE milliamperes,
where you are never supposed to be.  Little kicks on the meter below ONE
milliampere on the scale are what you want.

Now back to the spikes...

The spikes look just like fault conditions to the amp.  To a protection
circuit that depends on sensing what would be destructive continuous
overdrive in microseconds and then engaging in a few milliseconds, the
spike looks exactly the same as driving the grid with a continuous PEP the
same as the spike peak power.

Whether a single un-faulted spike could DESTROY the grid in it's time is a
kind of Russian roulette question.  If the spike was on the leading edge of
every single CW baud in a contest, you have your answer.  Kind of like if
someone in a bullet proof vest was shot over and over, how long would he
last?

Absolutely, when the spike-ee is a pair of now very expensive 4CX1000A or
4CX800A, you start fault detection proceedings the microsecond after the
input goes over the engineered threshold.  Meaning a spikey rig simply
could NOT be used with an Alpha 91B through 8410.  You could reduce power
output so the spike was the normal PEP for full power drive.  But on the
output, on average it would look like you were running 1/2 or 1/3 power.
 Zounds.  Who would put up with that?

Hams should be loudly, blatantly, zealously, continuously,
in-their-face-nasty, heavy-push-back, we-won't-put-up-with-your-crap
against rigs with spike problems.  Kind of like cars that lose wheels at
highway speeds.  Just simply not permitted, ever.  Do it and somebody goes
to jail for negligence.  And anyone making spikes by how they use their ALC
should be buried under a pile of rotten cabbage heads and tomatoes.
 Spiking things up should have roughly the same social value as repeatedly
loudly passing wind at Christmas dinner.

 Should I tell you now what I really think?  I guess I have an attitude
about that  :>)

73, Guy.

On Sat, Jun 9, 2012 at 3:41 PM, Roy Morris <[hidden email]> wrote:

> David, what are you saying?  Do the GU74bs dislike or do they tolerate the
> spike?  You left out an important word in your previous statement.  Thanks,
> Roy  W4WFB
>
>
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[Bruce Beford-2]

A very good indication of an overdriven amplifier or otherwise distorted
signal is when you see energy on the wrong side of the (suppressed) carrier
of an SSB signal, as well as the expected sideband energy. This is obvious
on the P3, and has a completely different appearance than a signal that has
an intentionally wide transmitted audio bandwidth, but is otherwise "clean".

73,
Bruce, N1RX


> It is not unusual to see a wide variation in SSB signal bandwidths having
> nothing to do with improper operation or distortion products.




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[vk4tux]

Van , It seems you weren't interested in answering whether you use the P3
waterfall display or not,
however a clean signal regardless of audio bandwidth will have clean
straight sides on the column,
whereas a signal containing excessive IMD products will show horizontal
spikes protruding from what
should be straight sides.

Using the marker to the end of these spikes each side will indicate the
signal width including the short
 order splatter.

-----Original Message-----
From: [hidden email]
[mailto:[hidden email]] On Behalf Of Harold V
Sent: Saturday, 9 June 2012 4:46 AM
To: [hidden email]
Subject: [Elecraft] Interpretation of P3 display

I have a question for the group regarding interpretation of the P3 display
of SSB signals.

Primarily I use it to spot stations on quiet bands or spot openings on busy
bands.  But I am trying to gain a better understanding of what it is showing
me regarding the quality of signals as well.

I have my P3 set up to show the band width as a column and the span set to
+/- 25.  I have noticed that most SSB signals will remain within the bounds
of the column.  However, some SSB signals will exceed the width of the
column and will resemble a pyramid, occupying several kilohertz above and
below the column on voice peaks.  The proximity of the station does not
appear to matter as these observations apply to distant stations as well as
local stations.

Is this what is known as "splatter"?  Is the station overdriving their
transmitter or linear?  Is their ALC or compression too high?  Is the
frequency response of their microphone too wide?

A good friend of mine has a K3/P3 and we have discussed this at length and
come to the conclusion that we really don't understand what we are seeing.
Anyone on the list have comments as to what they have observed or an
explanation of what we are seeing?

Any relevant comments would be appreciated.

Thanks
Van
K0HCV
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