Subject:,Re: KPA3 for QRP

[Kenneth Christiansen]

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

To:
Robert Tellefsen <[hidden email]>, G4ILO <[hidden email]>,
[hidden email]
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



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[n6wg]

Hi Kenneth
A couple of people have measured their K3s
without the KPA3 and again with it.
The difference seems to be as follows.
In receive, no difference with or without
as far as current drain goes.
When transmitting at QRP levels with the
KPA3 in bypass mode, the TX current
drain is approx 600 mA more than if the
KPA3 were not installed.

So, for a base station with an ac power
supply, no big deal.  However, for a Field
Day rig, if you plan to run a QRP entry, those
extra 600 mA will all have to come from
your battery.  That either reduces the time
you can operate from that battery, or cause
you to change batteries sooner than you
would have to otherwise.

That seems to be the essential difference,
Kenneth.  I had hoped to use my K3 (still
to come) on FD, but I think I'll stick with
my K2 at 5W.  Much easier on my battery
and solar panels.

73, Bob N6WG

----- Original Message -----
From: "Kenneth A. Christiansen" <[hidden email]>
To: <[hidden email]>; <[hidden email]>;
<[hidden email]>
Sent: Tuesday, March 18, 2008 5:25 AM
Subject: Subject:,Re: [Elecraft] KPA3 for QRP

>
> Subject:
> Re: [Elecraft] KPA3 for QRP
> From:
> WILLIS COOKE <[hidden email]>
> Date:
> Mon, 17 Mar 2008 08:44:15 -0700 (PDT)
>
> To:
> Robert Tellefsen <[hidden email]>, G4ILO <[hidden email]>,
> [hidden email]
> 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
>
>
>

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Elecraft web page: http://www.elecraft.com