[Elecraft] KPA500 power output starts out low, then goes up

[Barthold Lichtenbelt]

Thanks all for all the suggestions!

Fred Cady privately suggested making sure my ALC and Mic gain are set correctly. I tuned that some more, and it is a lot better, but still doesn't immediately go to full power output. 

I will test without KPA500 next.

I have two antennas, so I can test with that too, to rule out antenna problems. 

As to answer your questions:

> Does the SWR also change?

Nope. Just power output. SWR graphs of my antenna are just fine (using a Rigexpert AA-600 antenna analyzer).

> Have you measured the output of the K3 with a separate watt meter?

I don't have one, but both the P3TXMON and the KPA power Leds show the effect.

> How are the three boxes connected? Are you using the AuxIO cable that comes with the KPA and KAT? 

Yes, using the 15pin cables from K3S to KPA500 and KAT500. No separate key line.  The P3 is connected with the RJ45 to dual serial connector cable.

> And lastly, might you have ALC enabled in the K3 menu? Anything you can tell me about the setup will be helpful.

Yes, TX ALC is ON (I never messed with that, had to look it up in the manual how to get it to show up even in the config).

ALC Threshold for the KPA500 is set to 210.

The K3S has these options: Second receiver, internal tuner (Set to bypass), frequency lock option, 4x 8 pole filters, DVR.

Again, thanks for the help and suggestions. Quite a friendly bunch of people here!

Barthold
AD0RM

-----Original Message-----
From: Elecraft [mailto:elecraft-bounces at mailman.qth.net] On Behalf Of ab2tc
Sent: Monday, November 14, 2016 6:22 PM
To: elecraft at mailman.qth.net
Subject: Re: [Elecraft] KPA500 power output starts out low, then goes up

Hi,

How about following Vic, 4X6GP's advice and test the K3 without the KPA500 in circuit? Your symptoms are exactly as if the K3 TX calibration is badly out of wack as he suggests. The fact that a band change makes it worse is a dead give-away. A band change makes the K3's ALC algorithm reset itself to defaults and these defaults are set by the TX gain calibration. Your situation seems a bit extreme, though, with only 20% initial power so there may be other problems. But please test this out without the KPA500 in circuit. And surely eliminate antenna problems by testing into a dummy load.

AB2TC - Knut

 


Bill Conkling wrote
> That hasn’t helped my KPA500.  I notice it particularly after a band 
> change.
> 
> …bill nr4c
> 
> 
>> On Nov 13, 2016, at 10:58 PM, Vic Rosenthal 4X6GP <

> k2vco.vic@

> > wrote:
>> 
>> Hi Barthold,
>> 
>> Maybe the K3S output is ramping up slowly. Do you notice this with 
>> the
>> KPA500 off? Running the TX Gain Calibration in the K3 Utility might 
>> help in that case.
>> 
>> 73,
>> Vic, 4X6GP
>> Rehovot, Israel
>> Formerly K2VCO
>> http://www.qsl.net/k2vco/
>> 
>> On 14 Nov 2016 00:51, Barthold Lichtenbelt via Elecraft wrote:
>>> Hi All,
>>> 
>>> 
>>> 
>>> Maybe you can help with something that is baffling me. My KPA500 
>>> doesn't go to full output until I have spoken my callsign (when 
>>> trying to get through a
>>> pileup) a few times. It starts off with 100 or so watts, and after a 
>>> few iterations rises to the full 500W output. I see this both on the 
>>> KPA500 LED bar, as well as on the P3 PEP output monitored by 
>>> P3TXMON.  My full setup is
>>> K3S+KPA500+KAT500+P3+P3TXMON. All devices run the latest released
>>> firmware.
>>> 
>>> 
>>> 
>>> Any thoughts much appreciated!
>>> 
>>> 
>>> 
>>> Barthold
>>> 
>>> AD0RM
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