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KX3 power reverts from 10W back to 5W

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Arno Dienhart

KX3 power reverts from 10W back to 5W

So I had set up in the park, with a charged 12V 17Ah battery connected. It
was a hot day but I was in the shade.

Every time I set power level to 10W and keyed the TX, it reverted back to 5W
instantly. Why?

The Volt meter showed 12.3 V at RX and dropped to 11.7V at TX. Was that the
reason (getting below 12V)?

Was the PA getting too hot? It never went below 5W.

Thanks for any tips,

73,

Arno

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wayne burdick

Re: KX3 power reverts from 10W back to 5W

Administrator

Hi Arno,

The KX3 requires 11.0 volts minimum on key-down for power output levels of greater than 5 W. We do this to ensure low IMD in SSB transmit mode, but it's good practice in general because most 12-V batteries can be damaged quickly if you let the voltage go much below 11.0 with a heavy load applied.

When you measured the voltage on key-down, were you using a voltmeter at the battery, or the one in the radio? You could have been dropping some voltage across the power supply wires (+ and - leads probably about the same), or in the KX3's DC input circuitry (reverse-polarity diode, current sense resistor, etc.). So even if you read 11.7 V, it's possible that you briefly dipped below that 11.0 threshold.

Try running it into a dummy load, using the same battery. What is the voltage on key-down? (Make sure to bypass the ATU or tune it into the dummy load for this test.)

73,
Wayne
N6KR

On Aug 5, 2013, at 2:49 PM, Arno Dienhart <[hidden email]> wrote:

> So I had set up in the park, with a charged 12V 17Ah battery connected. It
> was a hot day but I was in the shade.
>
>
>
> Every time I set power level to 10W and keyed the TX, it reverted back to 5W
> instantly. Why?
>
>
>
> The Volt meter showed 12.3 V at RX and dropped to 11.7V at TX. Was that the
> reason (getting below 12V)?
>
> Was the PA getting too hot? It never went below 5W.
>
>
>
> Thanks for any tips,
>
>
>
> 73,
>
>
>
> Arno
>
> ______________________________________________________________
> 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

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Arno Dienhart

Re: KX3 power reverts from 10W back to 5W

Hi Wayne,

I measured with the built-in meter. Sorry, I don't have a dummy load, so I
cannot test that. Next time I will connect two of the same sealed lead acid
batteries in parallel and see if something changes. No problem to use two.

Thank you for the explanation. At least I can be sure that nothing is wrong
with my KX3.

73,
Arno

-----Original Message-----
From: Wayne Burdick [mailto:[hidden email]]
Sent: Monday, August 05, 2013 17:02
To: Arno Dienhart
Cc: [hidden email]
Subject: Re: [Elecraft] KX3 power reverts from 10W back to 5W

Hi Arno,

The KX3 requires 11.0 volts minimum on key-down for power output levels of
greater than 5 W. We do this to ensure low IMD in SSB transmit mode, but
it's good practice in general because most 12-V batteries can be damaged
quickly if you let the voltage go much below 11.0 with a heavy load applied.

When you measured the voltage on key-down, were you using a voltmeter at the
battery, or the one in the radio? You could have been dropping some voltage
across the power supply wires (+ and - leads probably about the same), or
in the KX3's DC input circuitry (reverse-polarity diode, current sense
resistor, etc.). So even if you read 11.7 V, it's possible that you briefly
dipped below that 11.0 threshold.

Try running it into a dummy load, using the same battery. What is the
voltage on key-down? (Make sure to bypass the ATU or tune it into the dummy
load for this test.)

73,
Wayne
N6KR

On Aug 5, 2013, at 2:49 PM, Arno Dienhart <[hidden email]> wrote:

> So I had set up in the park, with a charged 12V 17Ah battery
> connected. It was a hot day but I was in the shade.
>
>
>
> Every time I set power level to 10W and keyed the TX, it reverted back
> to 5W instantly. Why?
>
>
>
> The Volt meter showed 12.3 V at RX and dropped to 11.7V at TX. Was
> that the reason (getting below 12V)?
>
> Was the PA getting too hot? It never went below 5W.
>
>
>
> Thanks for any tips,
>
>
>
> 73,
>
>
>
> Arno
>
> ______________________________________________________________
> 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

wayne burdick

Re: KX3 power reverts from 10W back to 5W

Administrator

Most likely your antenna load Z was on the low side, increasing TX current drain. Either excess TX current or supply voltage below 11 V can cause power to revert to 5 watts.

73,
Wayne
N6KR

----
http://www.elecraft.com

On Aug 5, 2013, at 5:46 PM, "Arno Dienhart" <[hidden email]> wrote:

> Hi Wayne,
>
> I measured with the built-in meter. Sorry, I don't have a dummy load, so I
> cannot test that. Next time I will connect two of the same sealed lead acid
> batteries in parallel and see if something changes. No problem to use two.
>
> Thank you for the explanation. At least I can be sure that nothing is wrong
> with my KX3.
>
> 73,
> Arno
>
> -----Original Message-----
> From: Wayne Burdick [mailto:[hidden email]]
> Sent: Monday, August 05, 2013 17:02
> To: Arno Dienhart
> Cc: [hidden email]
> Subject: Re: [Elecraft] KX3 power reverts from 10W back to 5W
>
> Hi Arno,
>
> The KX3 requires 11.0 volts minimum on key-down for power output levels of
> greater than 5 W. We do this to ensure low IMD in SSB transmit mode, but
> it's good practice in general because most 12-V batteries can be damaged
> quickly if you let the voltage go much below 11.0 with a heavy load applied.
>
> When you measured the voltage on key-down, were you using a voltmeter at the
> battery, or the one in the radio? You could have been dropping some voltage
> across the power supply wires (+ and - leads probably about the same), or
> in the KX3's DC input circuitry (reverse-polarity diode, current sense
> resistor, etc.). So even if you read 11.7 V, it's possible that you briefly
> dipped below that 11.0 threshold.
>
> Try running it into a dummy load, using the same battery. What is the
> voltage on key-down? (Make sure to bypass the ATU or tune it into the dummy
> load for this test.)
>
> 73,
> Wayne
> N6KR
>
>
>
> On Aug 5, 2013, at 2:49 PM, Arno Dienhart <[hidden email]> wrote:
>
>> So I had set up in the park, with a charged 12V 17Ah battery
>> connected. It was a hot day but I was in the shade.
>>
>>
>>
>> Every time I set power level to 10W and keyed the TX, it reverted back
>> to 5W instantly. Why?
>>
>>
>>
>> The Volt meter showed 12.3 V at RX and dropped to 11.7V at TX. Was
>> that the reason (getting below 12V)?
>>
>> Was the PA getting too hot? It never went below 5W.
>>
>>
>>
>> Thanks for any tips,
>>
>>
>>
>> 73,
>>
>>
>>
>> Arno
>>
>> ______________________________________________________________
>> 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
>
>
>
>
> ______________________________________________________________
> 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

Dominic Baines-3

Re: KX3 power reverts from 10W back to 5W

In reply to this post by Arno Dienhart

Arno,

Sure someone from Elecraft will respond with a technical
explanation...sounds a bit like default behaviour to me and also shows
there is a difference in the battery and the internal PA voltage and you
are maybe close to the fold back voltage.

If the supply voltage drops below 12V (I use 7AH SLA batteries so see
this often) then it can be lower at the PA internally (c11V + a bit)
when it is the KX3 folds back to 5W, no real warning it just does it. I
found it a bit annoying when I knew mine was running hot but then the
KX3 was designed with battery /P operation in mind (I assume). The KX3
does the same thing to protect the KX3 if the PA gets too hot (you could
try this, not sure it will damage the KX3 so be warned, I did this when
I fitted a heatsink to reduce the issue... set power out to 10W, key
down or send dah dah constantly with a keyer for a few minutes into a
dummy load (not on air!) to make it fun do this in bright sun and watch
the PA temp rise and rise and the rear metal panel gets hot, eventually
the temperature will exceed what is 'safe' and the power will reduce,
same thing happens for excess current say if a PA transistor is failing
or an antenna impedance/VSWR changes there are multiple reasons and a
few other situations all are designed to protect the KX3.

You could monitor the KX3 reported PA temperature and the KX3 reported
voltage and see when it happens so you know when to adjust the power out
level yourself or know when it is likely to happen.

I have a really nice light weight /P switch mode mains power supply it
provides 12.2V (was for a CCTV camera) the KX3 will never exceed 8W out
with it on CW, if you set 10W it folds back immediately to 5W.

72

Dom
M1KTA
On 05/08/13 22:49, Arno Dienhart wrote:

Stephen G4SJP

Re: KX3 power reverts from 10W back to 5W

I have found that with even a freshly charged 7Ah battery that the power
folds back, on some bands especially, even if the internal atu has found a
good match. However, in almost all cases setting the power output to 8W
rather than initially 10W it doesn't happen as much, at least not until the
battery voltage has fallen well below 12V.

73 Stephen G4SJP

On Tuesday, 6 August 2013, Dominic Baines wrote:

> Arno,
>
> Sure someone from Elecraft will respond with a technical
> explanation...sounds a bit like default behaviour to me and also shows
> there is a difference in the battery and the internal PA voltage and you
> are maybe close to the fold back voltage.
>
> If the supply voltage drops below 12V (I use 7AH SLA batteries so see this
> often) then it can be lower at the PA internally (c11V + a bit) when it is
> the KX3 folds back to 5W, no real warning it just does it. I found it a bit
> annoying when I knew mine was running hot but then the KX3 was designed
> with battery /P operation in mind (I assume). The KX3 does the same thing
> to protect the KX3 if the PA gets too hot (you could try this, not sure it
> will damage the KX3 so be warned, I did this when I fitted a heatsink to
> reduce the issue... set power out to 10W, key down or send dah dah
> constantly with a keyer for a few minutes into a dummy load (not on air!)
> to make it fun do this in bright sun and watch the PA temp rise and rise
> and the rear metal panel gets hot, eventually the temperature will exceed
> what is 'safe' and the power will reduce, same thing happens for excess
> current say if a PA transistor is failing or an antenna impedance/VSWR
> changes there are multiple reasons and a few other situations all are
> designed to protect the KX3.
>
> You could monitor the KX3 reported PA temperature and the KX3 reported
> voltage and see when it happens so you know when to adjust the power out
> level yourself or know when it is likely to happen.
>
> I have a really nice light weight /P switch mode mains power supply it
> provides 12.2V (was for a CCTV camera) the KX3 will never exceed 8W out
> with it on CW, if you set 10W it folds back immediately to 5W.
>
> 72
>
> Dom
> M1KTA
> On 05/08/13 22:49, Arno Dienhart wrote:
>
>> So I had set up in the park, with a charged 12V 17Ah battery connected. It
>> was a hot day but I was in the shade.
>>
>>
>> Every time I set power level to 10W and keyed the TX, it reverted back to
>> 5W
>> instantly. Why?
>>
>>
>> The Volt meter showed 12.3 V at RX and dropped to 11.7V at TX. Was that
>> the
>> reason (getting below 12V)?
>>
>> Was the PA getting too hot? It never went below 5W.
>>
>>
>> Thanks for any tips,
>>
>>
>> 73,
>>
>>
>> Arno
>>
>
> ______________________________**______________________________**__
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>
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>

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Arno Dienhart

Re: KX3 power reverts from 10W back to 5W

In reply to this post by wayne burdick

Wayne,

I can't confirm a low Z as I don't have an analyzer. If this helps to guess:
I was using the ZS6BKW version of the G5RV, with 70' of coax connected to
the window line from the doublet and no matching network between that
connection.

The ATU was able to achieve a 1.0:1 SWR. RX was exceptionally low-noise but
TX did not get a lot of contacts (may have been other factors).

73,
Arno

-----Original Message-----
From: Wayne Burdick [mailto:[hidden email]]
Sent: Monday, August 05, 2013 19:46
To: Arno Dienhart
Cc: <[hidden email]>
Subject: Re: [Elecraft] KX3 power reverts from 10W back to 5W

Most likely your antenna load Z was on the low side, increasing TX current
drain. Either excess TX current or supply voltage below 11 V can cause power
to revert to 5 watts.

73,
Wayne
N6KR

----
http://www.elecraft.com

On Aug 5, 2013, at 5:46 PM, "Arno Dienhart" <[hidden email]> wrote:

> Hi Wayne,
>
> I measured with the built-in meter. Sorry, I don't have a dummy load,
> so I cannot test that. Next time I will connect two of the same sealed
> lead acid batteries in parallel and see if something changes. No problem
to use two.

>
> Thank you for the explanation. At least I can be sure that nothing is
> wrong with my KX3.
>
> 73,
> Arno
>
> -----Original Message-----
> From: Wayne Burdick [mailto:[hidden email]]
> Sent: Monday, August 05, 2013 17:02
> To: Arno Dienhart
> Cc: [hidden email]
> Subject: Re: [Elecraft] KX3 power reverts from 10W back to 5W
>
> Hi Arno,
>
> The KX3 requires 11.0 volts minimum on key-down for power output
> levels of greater than 5 W. We do this to ensure low IMD in SSB
> transmit mode, but it's good practice in general because most 12-V
> batteries can be damaged quickly if you let the voltage go much below 11.0

with a heavy load applied.

>
> When you measured the voltage on key-down, were you using a voltmeter
> at the battery, or the one in the radio? You could have been dropping
> some voltage across the power supply wires (+ and - leads probably
> about the same), or in the KX3's DC input circuitry (reverse-polarity
> diode, current sense resistor, etc.). So even if you read 11.7 V, it's
> possible that you briefly dipped below that 11.0 threshold.
>
> Try running it into a dummy load, using the same battery. What is the
> voltage on key-down? (Make sure to bypass the ATU or tune it into the
> dummy load for this test.)
>
> 73,
> Wayne
> N6KR
>
>
>
> On Aug 5, 2013, at 2:49 PM, Arno Dienhart <[hidden email]> wrote:
>
>> So I had set up in the park, with a charged 12V 17Ah battery
>> connected. It was a hot day but I was in the shade.
>>
>>
>>
>> Every time I set power level to 10W and keyed the TX, it reverted
>> back to 5W instantly. Why?
>>
>>
>>
>> The Volt meter showed 12.3 V at RX and dropped to 11.7V at TX. Was
>> that the reason (getting below 12V)?
>>
>> Was the PA getting too hot? It never went below 5W.
>>
>>
>>
>> Thanks for any tips,
>>
>>
>>
>> 73,
>>
>>
>>
>> Arno
>>
>> ______________________________________________________________
>> 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
>
>
>
>
> ______________________________________________________________
> 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