[Elecraft] KXPA Power Output

Sun Apr 17 14:44:21 EDT 2016

*/I have found that to get a correct (calibration) done using the 
utility and to correct a issue with my K3
KPA500 that developed 2 years after I built it .......... I needed to 
use this dummy load for calibration.
https://www.rfparts.com/dummy-loads/dummy-50/m1426.html

All my other dummy loads would not let the Utility Calibrate correctly 
.........that said.

After loading the Bata firmware on my KX3 mcu2.32 dsp 1.32 I'm seeing 
issues with power out.
I had a issue with the original first design kit I built had very low 
out put I called customer service was sent a new RF deck which I 
installed my ATU on and tested all bands were 100 or 110 watts except 
the 40 meter band which is where I spend 99 % of my operating on cw.

On 40 the power out was around 85 w and occasionally as high as 89 watts 
but now I see a totally different story.

Watching the operation tab in the utility while running a rag chew full 
QSK I see the input power bouncing from 2.6 watts to 3.1 watts on key 
down it maintains 3.1 watt input Forward power is 82.5 watts out 
reflected is .2 swr is 1.0

I'm thinking something is software has changed the behavior of the amp 
it is advertised as a 100 watt amp it should have no issue getting to 
100 watts

My rest voltage is 14.1 the key down voltage is 12.4  the power supply 
is set to max which is 14.1 the 14 gauge zip power cable is what comes 
with a 100watt Icom the length is 4 foot there is no loss here that I 
can see to cause this low power output.
If I were to install this amp in the car on the battery it would do 60 
watts.

I'm thinking a bit of tweaking to the firmware is necessary to set the 
drive power a bit higher might solve the low power issue.
It's advertized as a 100 watt amp it should do 100 
watts..................in a car at 12 volts even.

And I should not need welding cable to supply the amp it voltage from 4 
ft away.

Art
ka9zap

/*
On 4/16/2016 11:33 PM, Tom Field wrote:
> Thanks for the replies.
> I have gone through the procedure again.
> I used the calibration procedure outlined on the Elecraft Website.
>
>
> Some observations. With no load I have 14.63 volts coming into the KXPA
> 100.
> With the radio and amplifier on and resting, the current is approx 0.3 Amps
>
> Steps
> Set the radio in the 160 meter band
> Set P Cal
> Closed the menu
> Set Pwr to CAL 75
> Confirmed the KXPA 100 Is in bypass
> Pressed Tune( I assume this is the button that says transmit)
> Current rose to .9 Amps
> If I took the pressure off the button, the current stayed up until I
> pressed it again
> The display showed 2 numbers  On top 1.1  Below 5.0
> Pressed the button again
> Normal Display returned
> Moved on to 80 meter band
> Same behaviour and findings
> Moved to 60 meter band
> Same
> 40 meters, 30 meters, 20 meters same with approximately same current
> 17 meters, Current went up to 1.21 Amps
> 15 meters 1.24 Amps
> 12 meters 1.45 Amps
> 10 meters 1.45 Amps
> 6 meters
> Display showed 3 instead of 5 and 1.68 amps
>
> Opened the menue and turned the PA to on
>
> Set the PA back to auto
>
> set power at 75 Watts
> Using the KXPA Utility
>                              Input Power                  Forward Power
> 160 m                         0.8                                48
> 80 m                           1.0                                50
> 60 m                           1.2                                52
> 40 m                           1.2                                51.4
> 30 m                           1.1                                56.8
> 20 m                           1.6                                59.2
> 17 m                           1.6                                82
> 15 m                           1.2                                51
> 12 m                           1.0                                49.5
> 10 m                           1.2                                50.3
> 6 m                             2.0                                60.6
>
> The only band that came close was 17 meters. I wonder if there is something
> about the calibration process. Accd to the notes from the Elecraft website
> "Press TUNE. The KX3 will transmit for a short while then stop. During this
> transmission, the KX3 and KXPA100 will determine what drive level is needed
> to get to 75 watts"
>
> I found if I pushed and held TUNE, it started transmitting and did not stop
> transmitting until I let off and pushed it again.
>
> Advice, suggestions welcome.
>
> Tom
> KN6DR
>
>
> On Sat, Apr 16, 2016 at 5:29 PM, Tom Field <docwatt at gmail.com> wrote:
>
>> I'm having difficulty getting more than about 70 to 80 watts out of the
>> KXPA 100. I have it connected to a KX3 with the Elecraft cable and have
>> gone through the calibration procedure as outlined in the owners manual and
>> in Fred Cady's excellent book.
>>
>> For Example if I go through the calibration procedure on 40 meters,
>> It appears to show a drive level of 5 watts to achieve 75 watt output.
>> If I transmit into a dummy load, with the power setting at 100 watts,
>> I have a drive power of about 2.6 watts and an output power of about 70
>> watts as shown in the KXPA Utility.
>>
>> Am I missing something?
>>
>> Tom
>> KN6DR
>>
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