[Elecraft] KX3 power reverts from 10W back to 5W

[Arno Dienhart]

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:n6kr at elecraft.com] 
Sent: Monday, August 05, 2013 19:46
To: Arno Dienhart
Cc: <elecraft at mailman.qth.net>
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" <ad at broadweave.net> 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:n6kr at elecraft.com]
> Sent: Monday, August 05, 2013 17:02
> To: Arno Dienhart
> Cc: elecraft at mailman.qth.net
> 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 <ad at broadweave.net> 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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