Re: KPA-1500 Efficiency As A Function of Input Power

Posted by Wes Stewart-2 on Aug 17, 2018; 6:20pm
URL: http://elecraft.85.s1.nabble.com/KPA-1500-Efficiency-As-A-Function-of-Input-Power-tp7644445p7644459.html

Do they?

I have a KPA500, not a '1500 but I run mine full tilt on RTTY.

Something to bear in mind in this discussion is that we run our equipment in
ICAS, not CCS.  Even in a contest situation we probably only transmit half the
time.  During the off (RX) time the amp isn't drawing any plate, collector or
drain current, nor is it drawing much current on CW, key up or SSB between
syllables. RTTY is a "continuous" mode without the syllabic breather, but it's
still intermittent.

Wes

On 8/17/2018 6:43 AM, [hidden email] wrote:

> So why do most RTTY users run their amps at reduced power?
>
> John KK9A
>
>
> From: Charlie K3ICH
> Date: Fri Aug 17 09:24:18 EDT 2018
>
>
> I really do NOT understand why this data is so surprising.
> It all seems to me to be perfectly normal with the amplifier's highest
> efficiency occurring at near max output.
> Which curiously, I would assume,  is the way the amp was designed.
>
> Think zero output with zero drive = zero efficiency.
> Apply some drive, read some output and the efficiency goes up from there.
>
> 73, Charlie k3ICH
>
>
>
>
> -----Original Message-----
> From: elecraft-bounces at mailman.qth.net <elecraft-bounces at
> mailman.qth.net> On
> Behalf Of john at kk9a.com
> Sent: Friday, August 17, 2018 8:57 AM
> To: elecraft at mailman.qth.net
> Cc: charles at k5ua.com
> Subject: [Elecraft] KPA-1500 Efficiency As A Function of Input Power
>
> Interesting data, Charles.  I assumed that running the KPA1500 (or KPA500)
> at lower power would keep the fan from running as much. I knew that
> efficiency changed with output power but I did not expect that it was this
> significant. If your data is correct there is 1000++ watts of heat to
> dissipate no matter what power level you use.
>
> John KK9A
>
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