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walter renner

KPA500

I have KPA500 #429, and I really love the amp, but have been confused by the ALC threshold settings.

Maybe someone on this list can help me with a question I have concerning what it operation.

The ALC settings are from 0 to 210, and I find that it has no effect on power out regardless of where I set ALC.
The power out remains the same whatever the settings. Nothing changes from 0 to 210 on power out. Any ideas setting has the least effect on
power out or what setting has the most effect.

Kurt K0ARO
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Don Wilhelm-4

Re: KPA500

Kurt,

Have you set the drive power level as indicated on page 9 of the KPA500
manual?
After setting the drive power level, run the KPA500 at full power output
and then adjust the ALC Threshold as indicated on page 10 of the manual.

If you are not driving the KPA500 to full output, you should see no
change when adjusting the ALC Threshold. Remember that the ALC signal
is communicated back to the driving transceiver telling it to reduce its
power output. If you are using an early K3, has the mod for handling
negative going ALC been installed? Have you set the K3 EXT ALC menu
parameter as indicated on page 27 of the K3 manual?

It is best to make those adjustments into a dummy load capable of
handling 500 watts or more. If you do not have a suitable dummy load,
use whichever antenna provides you with a low SWR - the closer to SWR=1
the better the results of your settings.

73,
Don W3FPR

On 10/29/2011 11:23 AM, walter renner wrote:

> I have KPA500 #429, and I really love the amp, but have been confused by the ALC threshold settings.
>
> Maybe someone on this list can help me with a question I have concerning what it operation.
>
> The ALC settings are from 0 to 210, and I find that it has no effect on power out regardless of where I set ALC.
> The power out remains the same whatever the settings. Nothing changes from 0 to 210 on power out. Any ideas setting has the least effect on
> power out or what setting has the most effect.
>
>
> Kurt K0ARO
> ______________________________________________________________
> 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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Jack Brindle-2

Re: KPA500

In reply to this post by walter renner

Walter;

You don't mention what radio you are using with the KPA500. If it is the K3, do you have ALC turned on in the K3? And, do you have the KPA500's ALC output connected to the radio's ALC input pin? Also remember that the ALC setting does not affect KPA500 power, but rather radio output power. We do not recommend its use with the K3.

The ALC setting corresponds to a threshold value. When the exciter's output exceeds the threshold, the KPA500's ALC output will decrease (it goes from 0 to -12V) in order to reduce transmitter power. At a setting of 210 the transmitter's power level pretty much will not be affected, while at 0 the transmitter will not be putting out any power.

Having said all this, I will also add that the use of ALC with ham amplifiers is very argumentative. Proper adjustment of the transmitter will eliminate the need. With the K3's power settings for the KPA500 along with its design, you should never need it.

Jack Brindle, W6FB

On Oct 29, 2011, at 8:23 AM, walter renner wrote: