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K3--Too much ALC creates energy on opposite sideband?

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Bob McGraw - K4TAX

Re: K3--Too much ALC creates energy on opposite sideband?

I find a lot of the opposite sideband splatter is originated from
mis-tuned amplifiers or amplifiers which are driven too hard. If it
isn't "linear" it is a splatter generator. And linear means just
that, linear. For an amp to be linear, it must amplify all signal
levels the same amount. Most amplifiers begin to show some degree of
signal compression at the upper power rating limits. Pushing one past
these limits even the slightest amount, generate significant amounts of
opposite sideband splatter.

73

Bob, K4TAX

On 8/28/2019 4:27 PM, Jim Brown wrote:

> On 8/28/2019 1:50 PM, Wes wrote:
>
> Yes. I regularly see signals from SSB ragchewers with splatter in the
> suppressed sideband only 10-15 dB below signal in the intentional
> sideband. The data in the link I posted was with a P3 on my second K3,
> with the K3 being measured into a dummy load.
>
> I've alerted guys on 6M about this, suggesting they turn down drive to
> their amplifier, and they said they didn't have an amplifier. When I
> asked what rig, it was one of the low-cost do-everything rigs from one
> of the big JA mfrs. When I posted this at the time, W4TV described the
> mechanism (I think I remember that it was a shortcominBefore Elecraft
> rigs took over Field Day, These cheap rigs (and even some much more
> expensive ones) have long been considered the scourge of Field Day.
>
> 73, Jim K9YC
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David Gilbert

Re: K3--Too much ALC creates energy on opposite sideband?

In reply to this post by Bob McGraw - K4TAX

So very true. I'm about as far removed from being an AM/audiophile type
of ham as you could imagine, but I've heard guys getting "great audio"
reports when they sounded like trash with lots of clipping. It's really
sad, and I tend to err on the conservative side because I'd rather give
up a bit of "punch" than be one of them.

73,
Dave AB7E

On 8/28/2019 7:46 PM, Bob McGraw K4TAX wrote:
> In looking at my P3 and SSB signals on the bands, there are lots and
> lots of really bad signals. Yet I most often hear "great signal"
> given as a report.
>
> 73
>
> Bob, K4TAX

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Conrad PA5Y

Re: K3--Too much ALC creates energy on opposite sideband?

In reply to this post by Michael Walker

I have measured the TX IMD performance of my and 2 other K3S transceivers. In my opinion it is not possible to have anything other than mediocre TX IMD performance from a K3S or a K3 at ANY power level. I am so disappointed with this aspect of the K3S. The mass market and cheap IC-7300 is better, especially on 6m. In all other respects I am very impressed with the K3S.

The transverter output on 10m when set to 0.5mW has incredibly good IMD performance so the problem is with the 2 PA modules. I have contacted Elecraft and so far they have not offered me a satisfactory solution. I think that I am going to go to the inconvenience of using an external PA on 6m.

The K3S has excellent TX composite noise all ruined by poor TX IMD. I can easily see 19th and 21st order IMD components on 6m in the 90dB dynamic range of my E4406A spectrum analyser - this rather negates the advantage to my neighbours when I'm on SSB. For CW and Digimodes then the K3S is superb. If I was contemplating the purchase of a K4 I would be asking Elecraft about TX IMD from the hopefully new and improved TX amplifier chain.

Not a happy message but it's the truth. Yes I have the latest FW, yes I have tried to reduce the gain from the driver using the settings in the FW yes I maintain the correct voltage on the PA, yes I have late (not the latest) revisions of the driver and final PA. I am using the 2 tone facility so there is no question of external or maladjusted audio non linearity. The fact is that it is poor. I also know what I'm doing.

Poor show Elecraft!

73

Conrad PA5Y

________________________________
From: [hidden email] <[hidden email]> on behalf of Michael Walker <[hidden email]>
Sent: 29 August 2019 04:02
To: [hidden email] <[hidden email]>
Subject: Re: [Elecraft] K3--Too much ALC creates energy on opposite sideband?

Hi Fred (Skip)

Sadly, many of those are splattering so wide that you can hear them on the
opposite sideband. Unfortunately, a report of great audio does not mean
great IMD performance.

Don't take this the wrong way, I am not saying you have bad IMD it just
that you can't relate the 2 has being an indicator.

With a good radio and a good waterfall you can see it plain as day. There
are a few locals (aka here in ve3 land) that I 'watch' routinely with their
top end Yaesu's (5000's) and they sound awesome, but they have the absolute
worst splatter you have ever seen. One guy on 80M was absolutely
understandable when I listened to him on USB.

Nate, glad you got it figured out. I'm sure we have all been there (me
included).

73 all, Mike va3mw

On Wed, Aug 28, 2019 at 9:43 PM Nate Bargmann <[hidden email]> wrote:

> I think I better take a mea culpa on this one. One reply in a private
> email asked if I was using and amp and whether I was driving it too
> hard. Well, some mornings this week I have depending on static levels
> and I operated the KS QSO Party this past weekend and ran 100W. I
> normally run the amp (ALS-600) with the power setting at 70W.
>
> This is probably just a, "D'oh!" moment. Yes, the K3 was still set for
> 100W.
>
> Incidentally, My COMP runs about 2-3 bars on voice peaks and the ALC
> meter is in the 5-7 bars range on peaks as well.
>
> It's a PEBCAK3 issue. ;-)
>
> --
>
> "The optimist proclaims that we live in the best of all
> possible worlds. The pessimist fears this is true."
>
> Web: https://www.n0nb.us
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>
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Wes Stewart-2

Re: K3--Too much ALC creates energy on opposite sideband?

In reply to this post by k6dgw

This thread instigated some experiments here. In analyzing TX IMD in both my K3
and K3S, I've made probably hundreds of two-tone measurements using the built-in
two-tone generator. But in all of these measurements I never questioned what
the audio level was, since it's not adjustable, except for balancing the levels
of the tones. So I set up a measurement and went to transmit and then using the
K3 utility used the get "BG" command to read the ALC bar graph. The answer was
zero bars. I found this interesting.

To explore further, as a proxy audio signal generator, I opened WSJT-X, FT-8
mode and used the "Test" button to generate an audio tone. I used both the K3S
internal sound card and the built-in card in a Lenovo Think Pad as a double
check against generator distortion. I saw similar results with both.

And what are those results you ask.

Using a spectrum analyzer and looking at the K3S output on 14 MHz in this case,
using a low tone (500+ Hz) I noted that at any audio level that drove the ALC
indicator to four bars (even flickering), there was low level garbage that
appeared in the TX passband. It took reducing the level to three bars to clean
it up and in my radio there are either three bars or none, no one or two, when
reducing the gain. The "BG" command confirmed this. Above four bars, things
only got worse. Understand this was low-level stuff down in the weeds and not
the dreaded audio harmonics that WSJT-X "split" is supposed to prevent.

I've never been one of those handwringers worrying about using ALC, as I believe
just like AGC in receivers that we all use, properly designed it should work
well for its intended purpose. Now, I'm not so sure, perhaps I've been wrong or
I'm saved by the "properly designed" clause.

Wes N7WS

On 8/28/2019 2:22 PM, Fred Jensen wrote:

> Yes, I know what the manual says. However the IMD on my K3 goes up when I set
> the mic gain to flicker bar 7 on voice peaks so I run it with almost no ALC.
> I also set the TX EQ using the "K9YC Method," and regularly get unsolicited
> "great audio" comments so I'm a fairly happy ham.
>
> I'm not on SSB often, but when I do get on such as NAQP SSB, I'm always a bit
> surprised at how many signals have all the sideband energy crammed right up
> against the suppressed carrier. Not too many fill up their BW. For those of
> us with compromised hearing, it makes copy difficult ... one of the several
> reasons I don't get on phone very often. All that low frequency energy
> contributes almost nothing to intelligibility.
>
> 73,
> Fred ["Skip"] K6DGW
> Sparks NV DM09dn
> Washoe County
>

Wes Stewart-2

Re: K3--Too much ALC creates energy on opposite sideband?

In reply to this post by Conrad PA5Y

Conrad and I have corresponded about this in the past.

He is absolutely correct in worrying about the IMD performance of the K4. I
bought my K3S after being disappointed with the K3 TX IMD and thinking that the
FETs would be better. How wrong I was. IMD was no improvement and reliability
was awful. At 50 VDC, they no doubt would be better but as long as Elecraft
clings to "12-volt" radios, I'm afraid this will persist.

Wes N7WS

On 8/29/2019 5:04 AM, Conrad PA5Y wrote:

> I have measured the TX IMD performance of my and 2 other K3S transceivers. In my opinion it is not possible to have anything other than mediocre TX IMD performance from a K3S or a K3 at ANY power level. I am so disappointed with this aspect of the K3S. The mass market and cheap IC-7300 is better, especially on 6m. In all other respects I am very impressed with the K3S.
>
>
> The transverter output on 10m when set to 0.5mW has incredibly good IMD performance so the problem is with the 2 PA modules. I have contacted Elecraft and so far they have not offered me a satisfactory solution. I think that I am going to go to the inconvenience of using an external PA on 6m.
>
>
> The K3S has excellent TX composite noise all ruined by poor TX IMD. I can easily see 19th and 21st order IMD components on 6m in the 90dB dynamic range of my E4406A spectrum analyser - this rather negates the advantage to my neighbours when I'm on SSB. For CW and Digimodes then the K3S is superb. If I was contemplating the purchase of a K4 I would be asking Elecraft about TX IMD from the hopefully new and improved TX amplifier chain.
>
>
> Not a happy message but it's the truth. Yes I have the latest FW, yes I have tried to reduce the gain from the driver using the settings in the FW yes I maintain the correct voltage on the PA, yes I have late (not the latest) revisions of the driver and final PA. I am using the 2 tone facility so there is no question of external or maladjusted audio non linearity. The fact is that it is poor. I also know what I'm doing.
>
>
> Poor show Elecraft!
>
>
> 73
>
>
> Conrad PA5Y
>

K8TE

Re: K3--Too much ALC creates energy on opposite sideband?

In reply to this post by Michael Walker

There is a big difference between "energy on opposite sideband" and hearing
the opposite sideband. If you switch to the opposite sideband and can
clearly copy the intelligence, then the issue is sideband suppression. If
you hear unintelligible audio from the offending signal, that is splatter
with many possible causes, one of which is IMD in the exciter, amplifier, or
both.

ALC is frequently abused with the offending op receiving great audio
reports. I find many who never monitor ALC while operating SSB. Few ops
give accurate audio quality reports today, much less pay attention to TX
bandwidth when providing reports in spite of the proliferation of SDR's and
panadapters. Most don't know the difference between RFI in the TX audio
chain and an over-driven signal. We need to mentor our brethren to help
guide them in the right direction.

While some might consider this nitpicking, ours is a service based on
science and facts. However, science and facts are too often ignored. I use
screen captures from my P3 when pointing out broad signals. Half of the
offending ops don't have an e-mail on QRZ.com. Half of those who do are
surprised to learn of their transmitter bandwidth "abuse." A significant
portion of those don't care and are offended. Fortunately, that is rarely
the case here.

73, Bill, K8TE

"Sadly, many of those are splattering so wide that you can hear them on the
opposite sideband. Unfortunately, a report of great audio does not mean
great IMD performance."

--
Sent from: http://elecraft.365791.n2.nabble.com/
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Bob McGraw - K4TAX

Re: K3--Too much ALC creates energy on opposite sideband?

In reply to this post by Wes Stewart-2

Has anyone collected IMD data on the different version of KPA3A amps?
I seem to recall measuring IMD when I first got my K3S, s/n 10163.
Since that time I' have experienced 2 failures of the KPA3A in my
radio.   Elecraft replaced the last one with a newer "more stable"
version.   I do run my radio with 14.2 volts at the radio in transmit at
100 watts output CW key closed.   In RX the voltage is 14.5.    The 0.3
volt difference is the IR drop in the DC power cable and connector.

Guess I need to measure that one. But hey, it too pretty and very
comfortable outside.   I'll save that for another lousy weather day.

73

Bob, K4TAX

On 8/29/2019 12:09 PM, Wes wrote:

> Conrad and I have corresponded about this in the past.
>
> He is absolutely correct in worrying about the IMD performance of the
> K4. I bought my K3S after being disappointed with the K3 TX IMD and
> thinking that the FETs would be better. How wrong I was. IMD was no
> improvement and reliability was awful. At 50 VDC, they no doubt would
> be better but as long as Elecraft clings to "12-volt" radios, I'm
> afraid this will persist.
>
> Wes N7WS
>
>
> On 8/29/2019 5:04 AM, Conrad PA5Y wrote:
>> I have measured the TX IMD performance of my and 2 other K3S
>> transceivers. In my opinion it is not possible to have anything other
>> than mediocre TX IMD performance from a K3S or a K3 at ANY power
>> level. I am so disappointed with this aspect of the K3S. The mass
>> market and cheap IC-7300 is better, especially on 6m. In all other
>> respects I am very impressed with the K3S.
>>
>>
>> The transverter output on 10m when set to 0.5mW has incredibly good
>> IMD performance so the problem is with the 2 PA modules. I have
>> contacted Elecraft and so far they have not offered me a satisfactory
>> solution. I think that I am going to go to the inconvenience of using
>> an external PA on 6m.
>>
>>
>> The K3S has excellent TX composite noise all ruined by poor TX IMD. I
>> can easily see 19th and 21st order IMD components on 6m in the 90dB
>> dynamic range of my E4406A spectrum analyser - this rather negates
>> the advantage to my neighbours when I'm on SSB. For CW and Digimodes
>> then the K3S is superb. If I was contemplating the purchase of a K4 I
>> would be asking Elecraft about TX IMD from the hopefully new and
>> improved TX amplifier chain.
>>
>>
>> Not a happy message but it's the truth. Yes I have the latest FW, yes
>> I have tried to reduce the gain from the driver using the settings in
>> the FW yes I maintain the correct voltage on the PA, yes I have late
>> (not the latest) revisions of the driver and final PA. I am using the
>> 2 tone facility so there is no question of external or maladjusted
>> audio non linearity. The fact is that it is poor. I also know what
>> I'm doing.
>>
>>
>> Poor show Elecraft!
>>
>>
>> 73
>>
>>
>> Conrad PA5Y
>>
>
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Edward R Cole

Re: K3--Too much ALC creates energy on opposite sideband?

In reply to this post by Nate Bargmann

I assume the measurements with bare K3/K3S were using 100w internal
amp. I wonder how the 10w version of these radios Tx IMD perform?

On 6m, I run with the KXPA100 at 11w output (K3 at very low output)
to drive a 1000w Harris surplus TV linear (which is rated to 1600w
continuous duty). 1000w limit is due to the 50v-50A PS input
limit. On 2m+ I use the 1mw transverter interface output at 28-MHz
on my K3. My 2m 1500w and 23cm 600w LDMOS operate on 50v and I load
to 1-dB output compression point: 2m at 1200w, 23cm at 560w.

Any IMD analysis on the KXPA100?

73, Ed - KL7UW

From: Conrad PA5Y <[hidden email]>
To: Michael Walker <[hidden email]>, "[hidden email]"
<[hidden email]>
Subject: Re: [Elecraft] K3--Too much ALC creates energy on opposite
sideband?

I have measured the TX IMD performance of my and 2 other K3S
transceivers. In my opinion it is not possible to have anything other
than mediocre TX IMD performance from a K3S or a K3 at ANY power
level. I am so disappointed with this aspect of the K3S. The mass
market and cheap IC-7300 is better, especially on 6m. In all other
respects I am very impressed with the K3S.

73, Ed - KL7UW
http://www.kl7uw.com
Dubus-NA Business mail:
[hidden email]

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Peter Hall

Re: K3--Too much ALC creates energy on opposite sideband?

In reply to this post by Wes Stewart-2

Wes

Kenwood have delivered a very credible IMD performance from the new TS-890S and, indeed, even the TS-590s (especially the SG) are considerably better than the Elecraft offerings. All are 12 V radios, of course. I use a TS-890S with a KPA1500 and, while the combination is poorer in IMD terms than my 50-yo Collins S-line, it's a great deal better than many contemporary offerings. I don't anticipate parting with the TS-890S any time soon but, all things being equal, regard a K4 with good pre-distortion implementation as a deal maker in the not too distant future. Indeed, I might have waited for a K4 this time around, barring the shenanigans surrounding the K4 forum discussion and announcement.

Peter, VK6HP.

-----Original Message-----
From: [hidden email] <[hidden email]> On Behalf Of Wes
Sent: Friday, 30 August 2019 1:10 AM
To: [hidden email]
Subject: Re: [Elecraft] K3--Too much ALC creates energy on opposite sideband?

Conrad and I have corresponded about this in the past.

He is absolutely correct in worrying about the IMD performance of the K4. I bought my K3S after being disappointed with the K3 TX IMD and thinking that the FETs would be better. How wrong I was. IMD was no improvement and reliability was awful. At 50 VDC, they no doubt would be better but as long as Elecraft clings to "12-volt" radios, I'm afraid this will persist.

Wes N7WS

On 8/29/2019 5:04 AM, Conrad PA5Y wrote:

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