[Elecraft] KXPA Power Output

Sun Apr 17 22:27:18 EDT 2016

As I said, that’s true if you occasionally drive high SWR loads. There’s no downside in normal operation. And with a supply like the Astron, if you accidentally overload it, all you need do is cycle the power switch. 

73 Ron AC7AC

From: Walter Underwood [mailto:wunder at wunderwood.org] 
Sent: Sunday, April 17, 2016 5:05 PM
To: Ron D'Eau Claire; Elecraft Reflector
Subject: Re: [Elecraft] KXPA Power Output

Glad that a 20 A supply works for you, but the specs say:

"12-15 Vdc (13.8 V nominal), at least 24 A peak capacity. About 1 mA parasitic drain current whenever dc power is connected.”

So for the least problems, make sure that your supply can deliver 24 A peak, not 20 A peak.

wunder
K6WRU

Walter Underwood
CM87wj

http://observer.wunderwood.org/ (my blog)

On Apr 17, 2016, at 4:47 PM, Ron D'Eau Claire <ron at cobi.biz> 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:elecraft-bounces at mailman.qth.net] On Behalf Of Kevin Stover
Sent: Sunday, April 17, 2016 4:19 PM
To: elecraft at mailman.qth.net
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?

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