Elecraft

Fwd: Re: K3-P3 SSB spectrum

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k6dgw

Fwd: Re: K3-P3 SSB spectrum

I think understand this but then of course I thought I understood
Economics 101 in college which turned out to be seriously untrue ...

Turning the MIC GAIN way up on say an HT-37 increased the drive to the
PA and eventually saturated it, creating havoc on the band.

The K3 does not control power with the MIC GAIN. The PWR control sets a
"requested" power output. The internal power control loop then measures
the power level of the RF being made and adjusts it to meet the
requested level.

On SSB [and AFSK/DATA A] the MIC GAIN needs to be high enough so that
the power control loop can meet its target power, That's the first 4
bars of the ALC meter. Anything higher than that just lowers the system
gain til the target power is met. Or something like that [while waving
arms]...

I would imagine that turning the MIC GAIN way up would get a lot of
extraneous room noise onto your signal. I don't get on SSB all that
often, but mine is set for 4 bars with the 5th just flickering on peaks,
and 10 dB compression on peaks. Other people seem to like it when I
talk to them.

73,

Fred K6DGW
- Northern California Contest Club
- CU in the 50th Running of the Cal QSO Party 3-4 Oct 2015
- www.cqp.org

PS: There was never any doubt that I did *not* understand O'chem.

On 6/8/2015 10:56 AM, Richard Fjeld wrote:

> Just a comment somewhat related to this thread. Not long ago, a ham
> with an SDR set-up was comparing signals in a round-table for proper
> bandwidth.
>
> He said my signal was very clean and asked me to crank up my Mic gain
> to the max which I reluctantly did for a short transmission. He said
> it stayed clean with no splatter. Can that be? I thought any radio
> would splatter if over-driven.
>
> For me, seeing is believing. Dick, n0ce
>
>> Date: Sun, 7 Jun 2015 16:58:26 -0400 From: [hidden email] To:
>> [hidden email] Subject: Re: [Elecraft] K3-P3 SSB
>> spectrum
>>
>>
>> The TX Monitor is a time domain display - not a frequency domain
>> display. If you want to see the frequency domain display of your
>> own signal, temporarily disconnect the RS-232 cable between the two
>> (or connect another SDR to a directional coupler in the antenna
>> line).
>>
>> 73,
>>
>> ... Joe, W4TV

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Joe Subich, W4TV-4

Re: Fwd: Re: K3-P3 SSB spectrum

> The internal power control loop then measures the power level of the
> RF being made and adjusts it to meet the requested level.

There is *no "power control loop"* in the K3 - that is the difference
between the K3/K3S and traditional (YaeComWoood) transceivers. When
you (or the factory) performs the TX Gain calibration, the rig learns
how much (digital) gain is required in the DSP stage to drive the LPA
(5W setting) and the KPA3 (50W setting) to reach the desired power
level.

Since the transmit chain of the K3/K3S is linear (unlike YaeComWood),
when you request 100W instead of 50W the controller knows to increase
the voltage output of the DSP by a factor of 4 (3dB) while if you
request 20W the output of the DSP will be reduced by 4 dB (20/50 W =
-3.98 dB).

Because there is no "power control loop" the K3/K3S does not suffer
from overshoot, ALC induced distortions, IF clipping, PA over-drive,
etc. that plague traditional solid state transceivers.

73,

... Joe, W4TV

On 2015-06-08 5:16 PM, Fred Jensen wrote:

> I think understand this but then of course I thought I understood
> Economics 101 in college which turned out to be seriously untrue ...
>
> Turning the MIC GAIN way up on say an HT-37 increased the drive to the
> PA and eventually saturated it, creating havoc on the band.
>
> The K3 does not control power with the MIC GAIN. The PWR control sets a
> "requested" power output. The internal power control loop then measures
> the power level of the RF being made and adjusts it to meet the
> requested level.
>
> On SSB [and AFSK/DATA A] the MIC GAIN needs to be high enough so that
> the power control loop can meet its target power, That's the first 4
> bars of the ALC meter. Anything higher than that just lowers the system
> gain til the target power is met. Or something like that [while waving
> arms]...
>
> I would imagine that turning the MIC GAIN way up would get a lot of
> extraneous room noise onto your signal. I don't get on SSB all that
> often, but mine is set for 4 bars with the 5th just flickering on peaks,
> and 10 dB compression on peaks. Other people seem to like it when I
> talk to them.
>
> 73,
>
> Fred K6DGW
> - Northern California Contest Club
> - CU in the 50th Running of the Cal QSO Party 3-4 Oct 2015
> - www.cqp.org
>
> PS: There was never any doubt that I did *not* understand O'chem.
>
>
> On 6/8/2015 10:56 AM, Richard Fjeld wrote:
>> Just a comment somewhat related to this thread. Not long ago, a ham
>> with an SDR set-up was comparing signals in a round-table for proper
>> bandwidth.
>>
>> He said my signal was very clean and asked me to crank up my Mic gain
>> to the max which I reluctantly did for a short transmission. He said
>> it stayed clean with no splatter. Can that be? I thought any radio
>> would splatter if over-driven.
>>
>> For me, seeing is believing. Dick, n0ce
>>
>>> Date: Sun, 7 Jun 2015 16:58:26 -0400 From: [hidden email] To:
>>> [hidden email] Subject: Re: [Elecraft] K3-P3 SSB
>>> spectrum
>>>
>>>
>>> The TX Monitor is a time domain display - not a frequency domain
>>> display. If you want to see the frequency domain display of your
>>> own signal, temporarily disconnect the RS-232 cable between the two
>>> (or connect another SDR to a directional coupler in the antenna
>>> line).
>>>
>>> 73,
>>>
>>> ... Joe, W4TV
>
> ______________________________________________________________
> 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
> Message delivered to [hidden email]
>

Don Wilhelm-4

Re: Fwd: Re: K3-P3 SSB spectrum

Joe,

I disagree with you, but it may be only in semantics - there *must* be a
control loop to obtain proper power control. How that is implemented is
different in the K2, K3, and KX3 as compared with other transceivers
which only provide a knob to control the drive level and then depend on
"ALC" which in their definition is detection of overload to reduce the
drive level.

The K2, K3, KX3 does use a *closed* control loop for power control. The
actual power output is compared with the power requested by the Power
Knob, and the drive is adjusted by the MCU to make the two match. The
loop damping is set to minimize overshoot while also minimizing the
oscillation of the control loop. Ideally, that power control loop will
be 'critically damped' which will result in no overshoot and no loop
oscillation. The K3 achieves that critically damped condition in all
tests that I have done.

Yes, this enters into control loop theory, and the way the K2, K3, KX3
control power is unlike that seen in other amateur transceivers. Other
transceivers depend on detecting an overload condition (ALC) and as a
result reduce the drive level. The Elecraft transceivers do it differently.
The K2, K3, KX3 start at a lower power level (after a band change or
power level change) and ramp up to the requested level until they are equal.
The "downside" is that it takes some RF (a dit time or two, or a few SSB
sylables) for the K3 to come up to the requested power. The 'upside' is
that it is done with no overshoot and does not depend on detection that
some stage is being overdriven.
The actual output power is detected by the wattmeter which is right at
the output. That information is fed back to the MCU where it is
compared with the requested power and the MCU alters the drive as
required to make the two match.

That is why some operators have trouble with not providing adequate
audio drive for digital modes. If the audio level is too low, the drive
will be ramped up to (hopefully) provide the requested power output, and
that can result in "power hunting". The "conventional" wisdom given on
the internet for soundcard digital modes which is to run the power
control of the transceiver at max and use the audio drive to control the
power output does not work with Elecraft transceivers. One must first
set the audio level correctly (and then leave it alone) and adjust the
power level with the power request knob. Leave that "conventional"
wisdom to other transceivers (where it does work well), but do not use
it with your Elecraft gear.

73,
Don W3FPR

On 6/8/2015 7:44 PM, Joe Subich, W4TV wrote:

>
>> The internal power control loop then measures the power level of the
>> RF being made and adjusts it to meet the requested level.
>
> There is *no "power control loop"* in the K3 - that is the difference
> between the K3/K3S and traditional (YaeComWoood) transceivers. When
> you (or the factory) performs the TX Gain calibration, the rig learns
> how much (digital) gain is required in the DSP stage to drive the LPA
> (5W setting) and the KPA3 (50W setting) to reach the desired power
> level.
>
> Since the transmit chain of the K3/K3S is linear (unlike YaeComWood),
> when you request 100W instead of 50W the controller knows to increase
> the voltage output of the DSP by a factor of 4 (3dB) while if you
> request 20W the output of the DSP will be reduced by 4 dB (20/50 W =
> -3.98 dB).
>
> Because there is no "power control loop" the K3/K3S does not suffer
> from overshoot, ALC induced distortions, IF clipping, PA over-drive,
> etc. that plague traditional solid state transceivers.
>
> 73,
>
> ... Joe, W4TV