Subject:,Re: [Elecraft] KPA3 for QRP

[Kenneth A. Christiansen]

Subject:
Re: [Elecraft] KPA3 for QRP
From:
WILLIS COOKE <wrcooke at flash.net>
Date:
Mon, 17 Mar 2008 08:44:15 -0700 (PDT)

To:
Robert Tellefsen <n6wg at comcast.net>, G4ILO <julian.g4ilo at gmail.com>, 
elecraft at mailman.qth.net
CC:


People talk about the extra current drain.  How much
is it?  I don't have my K3 yet to make any tests and I
seldom run QRP (only when the other station wants 2
way QRP), but it would be of interest to us all if
anyone had measured the current draw of the K3 at
receive with and without the KPA3, transmit at 5 watts
without the KPA3 installed and transmit at 5 watts
with the KPA3 installed. I am sure that Elecraft has
the information, but I don' recall seeing it
published.  My guess is that the KPA3 does not require
much if any current when it is switched out.  Anybody
do any tests to know for sure?
+++++++++++++++++++++++++++++++++++++++++++++
I measured my currents at the 12 watt part of my build 
and again when the K3 was finished.
on 14.05 MHZ I measured TX 2.73 amps as a 12 watt K3
On 14.05 MHZ I measured TX 2.93 amps as a 120 watt K3
The receive current is 0.9 Amps either way.
The receive current can jump as high as 1.1 amps if the
fans are running.

The extra 0.2 amps is only taken in transmit mode.
If the XMIT button is hit it takes the extra 0.2 once
the 120 watt amp is installed. If full break in is 
used than the extra 0.2 amps is only used when the key
is down. If you did a field day using S and P and full
break in the extra current would be about an extra 
half amp hour. If you were calling CQ at 50 percent
transmit and full break in it would be about an extra
two amp hours. If you hit XMIT each time it would 
add about an extra 0.5 amp hourto the two amp hours. 
The K3-100 in receive for a 24 hours field day
will use about 24 amp hours plus 5 to 24 extra amp
hours in transmit depending on duty cycle. That makes
a total of 29 to 47 amp hours for a full 24 hour field
day.

A K2 can do the same field day in about 12 to 26 amp
hours. I find the K3 to have so much better receiver
and I operate S and P so it will plan to spend the
extra 17 to 18 amp hours for my field day.

73
Ken W0CZ