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KXPA Power Output

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Tom Field

KXPA Power Output

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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Bob N3MNT

Re: KXPA Power Output

Look at the actual voltage into the KXPA100 during transmit. This can happen if the voltage is below 13.8-14. I had to adjust my Astron 35 amp as at 13.5V I saw almost the same thing.

Nr4c

Re: KXPA Power Output

In reply to this post by Tom Field

You need to do the 70 watt cal with at lest 14 volts at amp power pole. And use biggest and shortest cable to minimize losses. Same power setup for operation.

Sent from my iPhone
...nr4c. bill

> On Apr 16, 2016, at 8:29 PM, Tom Field <[hidden email]> 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
> ______________________________________________________________
> 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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Tom Field

Re: KXPA Power Output

In reply to this post by Tom Field

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 <[hidden email]> wrote:

Arthur Nienhouse

Re: KXPA Power Output

*/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 <[hidden email]> 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
>>
> ______________________________________________________________
> 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]

David Orman

Re: KXPA Power Output

In reply to this post by Tom Field

Make sure the 3db attenuation switch on the back is set to out/auto, not
in. Had the same problem myself the other day.

David

On Sat, Apr 16, 2016 at 7:29 PM, Tom Field <[hidden email]> 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
> ______________________________________________________________
> 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]
>

Kevin Stover

Re: KXPA Power Output

In reply to this post by Arthur Nienhouse

WRU nailed it. I missed it in the original posting.
You're losing 1.7 volts in 8ft of that "#14 wire". That's about as bad
as it gets.
Why didn't you use the power cable supplied with the amp? I believe it's
#12.
What kind of power supply is running the amp? It has to be 25 amps peak
*minimum*, I'd say continuous. What else is being run on the same power
supply?

On 4/17/2016 4:19 PM, Walter Underwood wrote:

>> On Apr 17, 2016, at 11:44 AM, Art Nienhouse <[hidden email]> wrote:
>>
>> My rest voltage is 14.1 the key down voltage is 12.4 […]. 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.
> And there is your problem. The KXPA100 specs say "100 watts at 13.8 V”. It won’t produce 100W at 12.4V.
>
> A 1.7V drop under load is very large. The power supply and wiring cannot supply the required current without dropping the voltage.
>
> Eight feet of 14 gauge wire will have 0.9V drop at 24A. The electricity has to travel over both conductors of the 4 foot wire, which is why we use 8 feet.
>
> It looks like you have some additional problems beside the small power supply cable. Maybe there is resistance in the connectors (poor crimp? not seated?). Maybe the power supply won’t reliably supply 25A. Maybe the line voltage or house wiring has an issue.
>
> I would recommend at least 10 gauge wire and keeping the cables short. PowerWerx offers some useful pre-built cables at good prices.
>
> https://powerwerx.com/adapter-extension-cables
>
> wunder
> K6WRU
> Walter Underwood
> CM87wj
> http://observer.wunderwood.org/ (my blog)

Kevin Stover

Re: KXPA Power Output

I see your points. I'm just a little more conservative (paranoid) than
others.
I like a little headroom. I've got a pair of RS-35M's that are 24 and 20
years old. I can't kill em.

On 4/17/2016 6:47 PM, Ron D'Eau Claire wrote:

> A quality 20A peak supply is fine. For over a decade I've run a K3 and then a K3S and, when those aren't on a KX3/KXPA100 off of an Astron 20 without an issue as long as the finals see a decent SWR (current demand skyrockets as the SWR goes up). At low SWR's none of the rigs exceeds 18 to 19 amps, max.
>
> The 20 means 20A peak current - ICS rated (5 min on 5 min off). That Astron is rated at 16A continuous but Amateur stuff is almost never "continuous".
>
> Consider that 20A at 13.8VDC is 276 watts. As long as the rig is not way below 40% overall efficiency there will be no problem.
>
> That's using a quality linear supply. I'm not so casual about a switcher or a cheaper supply.
>
> I use the Elecraft supplied power cables on everything.
>
> 73, Ron AC7AC
>
> -----Original Message-----
> From: Elecraft [mailto:[hidden email]] On Behalf Of Kevin Stover
> Sent: Sunday, April 17, 2016 4:19 PM
> To: [hidden email]
> Subject: Re: [Elecraft] KXPA Power Output
>
> WRU nailed it. I missed it in the original posting.
> You're losing 1.7 volts in 8ft of that "#14 wire". That's about as bad as it gets.
> Why didn't you use the power cable supplied with the amp? I believe it's #12.
> What kind of power supply is running the amp? It has to be 25 amps peak *minimum*, I'd say continuous. What else is being run on the same power supply?
>
> ______________________________________________________________
> 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]
>

Elecraft mailing list

Re: KXPA Power Output

In reply to this post by Tom Field

Re: "WRU nailed it. I missed it in the original posting. You're losing 1.7 volts in 8ft of that "#14 wire"."

That's why Walter is known as "wunder"! <<grinning>>

I missed it, too :-(

Mark
ars: KE6BB

-------- Original message --------
From: Kevin Stover <[hidden email]>
Date: 04/17/2016 4:18 PM (GMT-08:00)
To: [hidden email]
Subject: Re: [Elecraft] KXPA Power Output

WRU nailed it. I missed it in the original posting.
You're losing 1.7 volts in 8ft of that "#14 wire". That's about as bad
as it gets.
Why didn't you use the power cable supplied with the amp? I believe it's
#12.
What kind of power supply is running the amp? It has to be 25 amps peak
*minimum*, I'd say continuous. What else is being run on the same power
supply?

On 4/17/2016 4:19 PM, Walter Underwood wrote:

--
R. Kevin Stover
AC0H
ARRL
FISTS #11993
SKCC #215
NAQCC #3441

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