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Kx3 power output

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Jim Dunstan

Kx3 power output

Hi

The KX3 specifications indicate a nominal 10 watts output. When
operating a mode such as PSK, which presents a continuous output,
what is the recommended power output? 10watts ? or something
less. given the normal amount of time between xmission and reception
in an average QSO?? Can the KX3 handle 10w output under these
conditions or should the power be reduced to a lower value?

Jim/VE3CI

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wayne burdick

Re: Kx3 power output

Administrator

Jim Dunstan wrote:

> The KX3 specifications indicate a nominal 10 watts output. When
> operating a mode such as PSK, which presents a continuous output,
> what is the recommended power output?

We recommend using 5 W for data modes and keeping transmissions
reasonably short. However, you can definitely use full power (up to 12
W) if the duty cycle is low, such as during hunt-and-pounce in a
contest. Of course as the duty cycle goes up, so will the PA and case
temperature, and eventually the KX3 may automatically roll back your
power output.

I just did a test using the built-in PSK-D mode, alternately
transmitting and receiving for 20 seconds each (simulating short
contest contacts). At 12 watts (20 meters), the temperature never got
high enough to roll back power during ten minutes of this.

I then tested the KX3's high-efficiency TX mode, which reduces current
drain by roughly 50% for a given power level. This mode kicks in at at
5.0 W or less in CW/FSK-D modes, and at 3.0 W or less in all other
modes. So I set power to 3.0 W in PSK-D mode, which is amazingly
effective given the S/N ratio of PSK31, and transmitted continuously.
After 5 minutes the PA temperature was still increasing slowly, but
I'm guessing I could have gone on for another 5-10 minutes.

The lesson, here, is to let the other station transmit once in awhile :)

Wayne
N6KR

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W7GJ, Lance

Re: Kx3 power output

Think it would work at 10 in JT65A mode? 48 seconds on and 72 seconds off, hour
after hour? VY 73, Lance

On 3/3/2012 12:17 AM, wayne burdick [via Elecraft] wrote:

> Jim Dunstan wrote:
>
> > The KX3 specifications indicate a nominal 10 watts output. When
> > operating a mode such as PSK, which presents a continuous output,
> > what is the recommended power output?
>
> We recommend using 5 W for data modes and keeping transmissions
> reasonably short. However, you can definitely use full power (up to 12
> W) if the duty cycle is low, such as during hunt-and-pounce in a
> contest. Of course as the duty cycle goes up, so will the PA and case
> temperature, and eventually the KX3 may automatically roll back your
> power output.
>
> I just did a test using the built-in PSK-D mode, alternately
> transmitting and receiving for 20 seconds each (simulating short
> contest contacts). At 12 watts (20 meters), the temperature never got
> high enough to roll back power during ten minutes of this.
>
> I then tested the KX3's high-efficiency TX mode, which reduces current
> drain by roughly 50% for a given power level. This mode kicks in at at
> 5.0 W or less in CW/FSK-D modes, and at 3.0 W or less in all other
> modes. So I set power to 3.0 W in PSK-D mode, which is amazingly
> effective given the S/N ratio of PSK31, and transmitted continuously.
> After 5 minutes the PA temperature was still increasing slowly, but
> I'm guessing I could have gone on for another 5-10 minutes.
>
> The lesson, here, is to let the other station transmit once in awhile :)
>
> Wayne
> N6KR
>
>
>
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Richard Ferch

Re: Kx3 power output

In reply to this post by Jim Dunstan

The question and response below only consider thermal limitations. There
are also signal quality limitations in some data modes, PSK31 in particular.

PSK31 is very intolerant of non-linearity. The "crest factor" of
PSK31 can be up to 2, i.e. the peak power can be twice the average
power. Since it is clipping of the peaks that causes splatter or IMD,
with most transmitters you need to keep the output power below one-half
the rated maximum in order to ensure linearity. Linearity is not nearly
as much of a problem in RTTY, but it matters in PSK31.

If you have the means to measure IMD of your transmitted PSK31 signal,
you can test this. A couple of years ago I did some tests using a
"PSKmeter" (a device that monitors a transmitted PSK31 signal and
reports the level of IMD products in the signal) observing the output of
my K3 in PSK31 with the K3 in DATA A mode. What I found was that IMD
levels were low at powers below 5 watts (KPA3 not in line) and at powers
above 12 watts but below 50 watts (KPA3 in line), but as the power was
increased above the 5 watt or 50 watt level, the measured IMD started to
increase quite rapidly. The reported IMD at full power (10 watts without
the KPA3 or 100 watts with the KPA3) was high - much higher than I would
consider acceptable.

I did not do similar tests in the K3's PSK D mode, but I have no reason
to believe they would be better. See W7AY's measurements of PSK31
quality in PSK D vs. DATA A (for power levels below 5W and 50W) at
<http://homepage.mac.com/chen/Technical/K3/Digital/digital.html>.

I would suggest to anyone who plans to transmit PSK31 at powers greater
than the recommended 5 watt (one-half full power) level that they should
monitor the quality of their transmitted signal to ensure that the
signal quality is acceptable. The simplest "low tech" way to do this is
to have another station report IMD figures for your signal at various
power levels. Note that the other station should be located such that
the signal they receive from you is neither too strong (a very strong
signal can produce IMD in the receiver) nor too weak (the signal must be
well above the noise level for the reported IMD measurement to be
meaningful).

In RTTY such precautions do not appear to be necessary. Qualitative
observations of the spectrum of my K3's RTTY signals in both FSK D and
AFSK A modes did not show a significant observable difference between
the signals at 50 watts and the signals at 100 watts.

73,
Rich VE3KI

Wayne Burdick wrote:

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Chip Stratton

Re: Kx3 power output

I think the usual preferred method for getting maximum PSK power
output is to set your transmitter for its maximum potential power
output, but adjust PSK modulation to a point below which ALC
activation (and hence signal peak clipping) is not occurring. As Rich
says, this typically will be at an average power output of one half
what the transmitter is capable of delivering in CW or RTTY mode. An
PSK IMD meter would be ideal, but using this method seems to work
fine. I do not have a K3, but with my IC-7000 I use this method,
though usually setting modulation levels such that average power
output is in the 20 to 40 watt range if I'm trying to reach a
difficult station.

Perhaps the adjustments on the K3 and KX3 are different if using
built-in PSK modulation?

Chip
AE5KA

On Fri, Mar 2, 2012 at 11:50 PM, Richard Ferch <[hidden email]> wrote:

> The question and response below only consider thermal limitations. There
> are also signal quality limitations in some data modes, PSK31 in particular.
>
> PSK31 is very intolerant of non-linearity. The "crest factor" of
> PSK31 can be up to 2, i.e. the peak power can be twice the average
> power. Since it is clipping of the peaks that causes splatter or IMD,
> with most transmitters you need to keep the output power below one-half
> the rated maximum in order to ensure linearity. Linearity is not nearly
> as much of a problem in RTTY, but it matters in PSK31.
>
> If you have the means to measure IMD of your transmitted PSK31 signal,
> you can test this. A couple of years ago I did some tests using a
> "PSKmeter" (a device that monitors a transmitted PSK31 signal and
> reports the level of IMD products in the signal) observing the output of
> my K3 in PSK31 with the K3 in DATA A mode. What I found was that IMD
> levels were low at powers below 5 watts (KPA3 not in line) and at powers
> above 12 watts but below 50 watts (KPA3 in line), but as the power was
> increased above the 5 watt or 50 watt level, the measured IMD started to
> increase quite rapidly. The reported IMD at full power (10 watts without
> the KPA3 or 100 watts with the KPA3) was high - much higher than I would
> consider acceptable.
>
> I did not do similar tests in the K3's PSK D mode, but I have no reason
> to believe they would be better. See W7AY's measurements of PSK31
> quality in PSK D vs. DATA A (for power levels below 5W and 50W) at
> <http://homepage.mac.com/chen/Technical/K3/Digital/digital.html>.
>
> I would suggest to anyone who plans to transmit PSK31 at powers greater
> than the recommended 5 watt (one-half full power) level that they should
> monitor the quality of their transmitted signal to ensure that the
> signal quality is acceptable. The simplest "low tech" way to do this is
> to have another station report IMD figures for your signal at various
> power levels. Note that the other station should be located such that
> the signal they receive from you is neither too strong (a very strong
> signal can produce IMD in the receiver) nor too weak (the signal must be
> well above the noise level for the reported IMD measurement to be
> meaningful).
>
> In RTTY such precautions do not appear to be necessary. Qualitative
> observations of the spectrum of my K3's RTTY signals in both FSK D and
> AFSK A modes did not show a significant observable difference between
> the signals at 50 watts and the signals at 100 watts.
>
> 73,
> Rich VE3KI
>
>
> Wayne Burdick wrote:
>
>> Jim Dunstan wrote:
>>
>>> The KX3 specifications indicate a nominal 10 watts output. When
>>> operating a mode such as PSK, which presents a continuous output,
>>> what is the recommended power output?
>>
>> We recommend using 5 W for data modes and keeping transmissions
>> reasonably short. However, you can definitely use full power (up to 12
>> W) if the duty cycle is low, such as during hunt-and-pounce in a
>> contest. Of course as the duty cycle goes up, so will the PA and case
>> temperature, and eventually the KX3 may automatically roll back your
>> power output.
>>
>> I just did a test using the built-in PSK-D mode, alternately
>> transmitting and receiving for 20 seconds each (simulating short
>> contest contacts). At 12 watts (20 meters), the temperature never got
>> high enough to roll back power during ten minutes of this.
>>
>> I then tested the KX3's high-efficiency TX mode, which reduces current
>> drain by roughly 50% for a given power level. This mode kicks in at at
>> 5.0 W or less in CW/FSK-D modes, and at 3.0 W or less in all other
>> modes. So I set power to 3.0 W in PSK-D mode, which is amazingly
>> effective given the S/N ratio of PSK31, and transmitted continuously.
>> After 5 minutes the PA temperature was still increasing slowly, but
>> I'm guessing I could have gone on for another 5-10 minutes.
>>
>> The lesson, here, is to let the other station transmit once in awhile :)
>>
>> Wayne
>> N6KR
>
> ______________________________________________________________
> Elecraft mailing list
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Richard Ferch

Re: Kx3 power output

In reply to this post by Jim Dunstan

Chip,

While this method of control for PSK31 (set power to maximum and use
audio drive controls to adjust output) works well with many rigs, it
does not work with the K3. If the ALC meter is showing fewer than 4
bars, output power will be unstable, and if the power control is set to
maximum, the K3 will do its best to achieve that power level, which is
not what you want.

With the K3 in DATA A (or AFSK A), the recommended procedure is to set
the audio drive at the level that results in 4-5 bars on the K3's ALC
meter, and then use the PWR control to adjust the output power. You can
think of the 4-5 bar point on the K3's ALC meter as the point where ALC
is just starting to activate.

With the K3 in PSK D mode, neither of these methods is possible. In PSK
D there is no audio drive to adjust; the only control available is the
PWR control.

73,
Rich VE3KI

Chip Stratton wrote:

> I think the usual preferred method for getting maximum PSK power
> output is to set your transmitter for its maximum potential power
> output, but adjust PSK modulation to a point below which ALC
> activation (and hence signal peak clipping) is not occurring. As Rich
> says, this typically will be at an average power output of one half
> what the transmitter is capable of delivering in CW or RTTY mode. An
> PSK IMD meter would be ideal, but using this method seems to work
> fine. I do not have a K3, but with my IC-7000 I use this method,
> though usually setting modulation levels such that average power
> output is in the 20 to 40 watt range if I'm trying to reach a
> difficult station.
>
> Perhaps the adjustments on the K3 and KX3 are different if using
> built-in PSK modulation?

Bruce Beford-2

Re: Kx3 power output

In reply to this post by Jim Dunstan

Rich is absolutely right on this. Also, since the original question was
regarding the KX3, I expect the KX3 to behave the same way. Set the drive
level for the appropriate ALC meter response, and then set the output power
level where you want it.

73,
Bruce, N1RX

> While this method of control for PSK31 (set power to maximum and use
> audio drive controls to adjust output) works well with many rigs, it
> does not work with the K3. If the ALC meter is showing fewer than 4
> bars, output power will be unstable, and if the power control is set to
> maximum, the K3 will do its best to achieve that power level, which is
> not what you want.

> With the K3 in DATA A (or AFSK A), the recommended procedure is to set
> the audio drive at the level that results in 4-5 bars on the K3's ALC
> meter, and then use the PWR control to adjust the output power. You can
> think of the 4-5 bar point on the K3's ALC meter as the point where ALC
> is just starting to activate.

> With the K3 in PSK D mode, neither of these methods is possible. In PSK
> D there is no audio drive to adjust; the only control available is the
> PWR control.

> 73,
> Rich VE3KI

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Don Wilhelm-4

Re: Kx3 power output

In reply to this post by Richard Ferch

I would like to amplify what Rich is saying:
With the K2, or K3 and I assume also the KX3, set the desired power
level with the power control and adjust the audio to fully drive the
radio just to the point of onset of ALC.

The proper audio level is determined by the ALC meter. With the K2,
increase the audio until you see 1 ALC bar and then back off until it
goes out.
With the K3 (and probably also the KX3) adjust for 4 ALC bars solid and
the 5th bar flickering.
The first 4 bars of the K3 ALC meter are not actually an indication of
ALC - they are more akin to a VU meter. The onset of ALC is at the 5th bar.

If you attempt to operate the K2 or K3 (and likely the KX3) using the
methods typically stated for other transceivers, they will "power hunt"
trying to produce the power set on the Power knob, but will be
"confused" because there is not enough audio to produce the requested
amount of power.

I cannot emphasize this point enough - the way the K2 and K3 control
power is different than that typically used by other transceivers.

73,
Don W3FPR

On 3/3/2012 9:52 AM, Richard Ferch wrote:

> Chip,
>
> While this method of control for PSK31 (set power to maximum and use
> audio drive controls to adjust output) works well with many rigs, it
> does not work with the K3. If the ALC meter is showing fewer than 4
> bars, output power will be unstable, and if the power control is set to
> maximum, the K3 will do its best to achieve that power level, which is
> not what you want.
>
> With the K3 in DATA A (or AFSK A), the recommended procedure is to set
> the audio drive at the level that results in 4-5 bars on the K3's ALC
> meter, and then use the PWR control to adjust the output power. You can
> think of the 4-5 bar point on the K3's ALC meter as the point where ALC
> is just starting to activate.
>
> With the K3 in PSK D mode, neither of these methods is possible. In PSK
> D there is no audio drive to adjust; the only control available is the
> PWR control.
>
> 73,
> Rich VE3KI
>
>
> Chip Stratton wrote:
>
>> I think the usual preferred method for getting maximum PSK power
>> output is to set your transmitter for its maximum potential power
>> output, but adjust PSK modulation to a point below which ALC
>> activation (and hence signal peak clipping) is not occurring. As Rich
>> says, this typically will be at an average power output of one half
>> what the transmitter is capable of delivering in CW or RTTY mode. An
>> PSK IMD meter would be ideal, but using this method seems to work
>> fine. I do not have a K3, but with my IC-7000 I use this method,
>> though usually setting modulation levels such that average power
>> output is in the 20 to 40 watt range if I'm trying to reach a
>> difficult station.
>>
>> Perhaps the adjustments on the K3 and KX3 are different if using
>> built-in PSK modulation?
> ______________________________________________________________
> Elecraft mailing list
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>

Joe Subich, W4TV-4

Re: Kx3 power output

In reply to this post by Bruce Beford-2

> Set the drive level for the appropriate ALC meter response, and then
> set the output power level where you want it.

But remember that PSK31 has an approximately 3 dB crest factor (peak
to average ratio). To prevent the K3 and presumably KX3 amplifiers
from saturating and generating a very wide signal, the maximum power
in PSK31 should be between 40 and 50% of the maximum available. With
the K3 power control set for 40 to 50 watts, instantaneous PEP output
will be 100 to 110 W even though the typical PEP reading wattmeter may
only show 45 W.

73,

... Joe, W4TV

On 3/3/2012 9:58 AM, Bruce Beford wrote:

> Rich is absolutely right on this. Also, since the original question was
> regarding the KX3, I expect the KX3 to behave the same way. Set the drive
> level for the appropriate ALC meter response, and then set the output power
> level where you want it.
>
> 73,
> Bruce, N1RX
>
>> While this method of control for PSK31 (set power to maximum and use
>> audio drive controls to adjust output) works well with many rigs, it
>> does not work with the K3. If the ALC meter is showing fewer than 4
>> bars, output power will be unstable, and if the power control is set to
>> maximum, the K3 will do its best to achieve that power level, which is
>> not what you want.
>
>> With the K3 in DATA A (or AFSK A), the recommended procedure is to set
>> the audio drive at the level that results in 4-5 bars on the K3's ALC
>> meter, and then use the PWR control to adjust the output power. You can
>> think of the 4-5 bar point on the K3's ALC meter as the point where ALC
>> is just starting to activate.
>
>> With the K3 in PSK D mode, neither of these methods is possible. In PSK
>> D there is no audio drive to adjust; the only control available is the
>> PWR control.
>
>> 73,
>> Rich VE3KI
>
>
>
>
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Jim Dunstan

Re: Kx3 power output

In reply to this post by Richard Ferch

At 12:50 AM 3/3/2012, you wrote:

Hi Rich,

A very thoughtful response. PSK31 is one of my favourite modes. I
have used several different xcvrs ... at the moment I am using a
Kenwood TS-50 and I have setup another xcvr (an old Ten Tec) as a
monitor. As you point out the signal must be kept below S9 in the
monitor rcvr in order to get an accurate read on the IMD of the
transmitted signal. I did the tests into a dummy load. The TS-50 is
primarily designed as a mobile SSB xcvr ... however I find it
provides excellent IMD (in the -30db area) when I set it for full
power and set the PSK31 audio level that produces 15 watts RF
output. Beyond the level the IMD figures drop rapidly. I generally
operate in the 10-15 Watt output level and I seem to be able to work
anyone I hear ... including a lot of DX (with my rotatable dipole at
16M height).

I expect the KX3 will work vy well at 5 watts output. When the KXPA3
comes out I would expect to be able to generate a clean signal in
that 15-20 watt range..

Jim, VE3CI

>The question and response below only consider thermal limitations. There
>are also signal quality limitations in some data modes, PSK31 in particular.
>
>PSK31 is very intolerant of non-linearity. The "crest factor" of
>PSK31 can be up to 2, i.e. the peak power can be twice the average
>power. Since it is clipping of the peaks that causes splatter or IMD,
>with most transmitters you need to keep the output power below one-half
>the rated maximum in order to ensure linearity. Linearity is not nearly
>as much of a problem in RTTY, but it matters in PSK31.
>
>If you have the means to measure IMD of your transmitted PSK31 signal,
>you can test this. A couple of years ago I did some tests using a
>"PSKmeter" (a device that monitors a transmitted PSK31 signal and
>reports the level of IMD products in the signal) observing the output of
>my K3 in PSK31 with the K3 in DATA A mode. What I found was that IMD
>levels were low at powers below 5 watts (KPA3 not in line) and at powers
>above 12 watts but below 50 watts (KPA3 in line), but as the power was
>increased above the 5 watt or 50 watt level, the measured IMD started to
>increase quite rapidly. The reported IMD at full power (10 watts without
>the KPA3 or 100 watts with the KPA3) was high - much higher than I would
>consider acceptable.
>
>I did not do similar tests in the K3's PSK D mode, but I have no reason
>to believe they would be better. See W7AY's measurements of PSK31
>quality in PSK D vs. DATA A (for power levels below 5W and 50W) at
><http://homepage.mac.com/chen/Technical/K3/Digital/digital.html>.
>
>I would suggest to anyone who plans to transmit PSK31 at powers greater
>than the recommended 5 watt (one-half full power) level that they should
>monitor the quality of their transmitted signal to ensure that the
>signal quality is acceptable. The simplest "low tech" way to do this is
>to have another station report IMD figures for your signal at various
>power levels. Note that the other station should be located such that
>the signal they receive from you is neither too strong (a very strong
>signal can produce IMD in the receiver) nor too weak (the signal must be
>well above the noise level for the reported IMD measurement to be
>meaningful).
>
>In RTTY such precautions do not appear to be necessary. Qualitative
>observations of the spectrum of my K3's RTTY signals in both FSK D and
>AFSK A modes did not show a significant observable difference between
>the signals at 50 watts and the signals at 100 watts.
>
>73,
>Rich VE3KI
>
>
>Wayne Burdick wrote:
>
> > Jim Dunstan wrote:
> >
> >> The KX3 specifications indicate a nominal 10 watts output. When
> >> operating a mode such as PSK, which presents a continuous output,
> >> what is the recommended power output?
> >
> > We recommend using 5 W for data modes and keeping transmissions
> > reasonably short. However, you can definitely use full power (up to 12
> > W) if the duty cycle is low, such as during hunt-and-pounce in a
> > contest. Of course as the duty cycle goes up, so will the PA and case
> > temperature, and eventually the KX3 may automatically roll back your
> > power output.
> >
> > I just did a test using the built-in PSK-D mode, alternately
> > transmitting and receiving for 20 seconds each (simulating short
> > contest contacts). At 12 watts (20 meters), the temperature never got
> > high enough to roll back power during ten minutes of this.
> >
> > I then tested the KX3's high-efficiency TX mode, which reduces current
> > drain by roughly 50% for a given power level. This mode kicks in at at
> > 5.0 W or less in CW/FSK-D modes, and at 3.0 W or less in all other
> > modes. So I set power to 3.0 W in PSK-D mode, which is amazingly
> > effective given the S/N ratio of PSK31, and transmitted continuously.
> > After 5 minutes the PA temperature was still increasing slowly, but
> > I'm guessing I could have gone on for another 5-10 minutes.
> >
> > The lesson, here, is to let the other station transmit once in awhile :)
> >
> > Wayne
> > N6KR
>
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Jim Dunstan

Re: Kx3 power output

In reply to this post by Bruce Beford-2

At 09:58 AM 3/3/2012, you wrote:
>Rich is absolutely right on this. Also, since the original question was
>regarding the KX3, I expect the KX3 to behave the same way. Set the drive
>level for the appropriate ALC meter response, and then set the output power
>level where you want it.
>
>73,
>Bruce, N1RX

Hi Bruce,

I expect you are correct ... a different method of setting the
output. The strategy described by chip is the method I use with my
old Kenwood TS-50. But since the TS-50 has no ALC indication I used
the monitoring method to determine the amount of drive that initiates
a drop in IMD. The TS-50 is rated at 100W PEP output on SSB ...
however careful monitoring indicates the IMD drops dramatically
beyond 15W output! I operate between 10 and 15 watts and get great
reports. I will have to get used to KX3 method of controlling power output.

Jim, VE3CI

> > While this method of control for PSK31 (set power to maximum and use
> > audio drive controls to adjust output) works well with many rigs, it
> > does not work with the K3. If the ALC meter is showing fewer than 4
> > bars, output power will be unstable, and if the power control is set to
> > maximum, the K3 will do its best to achieve that power level, which is
> > not what you want.
>
> > With the K3 in DATA A (or AFSK A), the recommended procedure is to set
> > the audio drive at the level that results in 4-5 bars on the K3's ALC
> > meter, and then use the PWR control to adjust the output power. You can
> > think of the 4-5 bar point on the K3's ALC meter as the point where ALC
> > is just starting to activate.
>
> > With the K3 in PSK D mode, neither of these methods is possible. In PSK
> > D there is no audio drive to adjust; the only control available is the
> > PWR control.
>
> > 73,
> > Rich VE3KI
>
>
>
>
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