[Elecraft] KXPA Power Output

[Mark, KE6BB]

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 <kevin.stover at mediacombb.net> 
Date: 04/17/2016  4:18 PM  (GMT-08:00) 
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?

On 4/17/2016 4:19 PM, Walter Underwood wrote:
>> On Apr 17, 2016, at 11:44 AM, Art Nienhouse <ka9zap at gmail.com> 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)


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



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