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Date: Mon, 22 Apr 2002 15:25:01 -0700
From: Eric Swartz WA6HHQ - Elecraft <eric at elecraft.com>
Organization: Elecraft
To: elecraft at mailman.qth.net
Subject: Re: [Elecraft] K2 in Overdrive Mode: 20 watts ?

Hi Jim,

We emphatically do not recommend trying to run the K2 above 15W, especially in
SSB operation. In SSB operation you will see seriously degraded IMD distortion,
especially on the bands above 20M, if you run well over 15W. 

While on CW you can tolerate some flat topping when operating above 15W (the low
pass filter takes out the 3rd order harmonic), you will be removing the cw
shaping circuitry, built in power dissipation headroom, over current and SWR
protection that makes the K2's PAs so rugged. Also, you will be exceeding the
design level for our PA heatsink. Not a good idea.

Stay tuned - The K2/100 will be shipping by Dayton (May 19th).

73, Eric  WA6HHQ
Elecraft
==============

> ----- Original Message -----
> From: JimWMiller at aol.com
> Sent: Monday, April 22, 2002 3:10 PM
> Subject: [Elecraft] K2 in Overdrive Mode: 20 watts ?
> 
> It is my understanding that the K2 is capable of about 20 watts output on the
> lower bands if the power supply is run at 15 volts and the high voltage 
> output protection  circuit is defeated.
> 
> Is anyone getting 20+ watts in this "over-drive" mode?
> 
> I realized that this is pushing the rig to the max but I enjoy "life in the fast lane".
> 73,
> Jim Miller, WA2UMP

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Date: Mon, 22 Apr 2002 13:42:35 -0700
From: Vic Rosenthal <rakefet at rakefet.com>
Organization: Transparent Software
To: Elecraft <elecraft at mailman.qth.net>
Subject: Re: [Elecraft] K2 in Overdrive Mode: 20 watts ?

JimWMiller at aol.com wrote:

> If you're getting the 20 watts please share your experience.
> - What power supply are you using and how much current does it pull?
> - How hot does the final and drive get during transmission?
> - Any problems?

I tried this for a while because I wanted more output to drive a high-powered
amp.  I decided it was NOT a good idea.  Here's the message I posted after my
experimenting was over:
-------------------------------------
Well, I have undone my high-power K2 experiments and am back to 15 watts.  By
adjusting the FWD control in the KAT2 to fool the firmware, upping CAL CUR to
4.5, turning up the power supply to about 16v (which gave about 15v after the
fuse and protective diode in the K2) and adding a turn to the secondary of the
final output transformer, I got

160-40m  22 watts
30-17m   20
15m      18
12-10m   16

This was enough to drive my amplifier to reasonable output.  However, on the
downside:

1) On 10/12 m, if I advanced the power control beyond the point at which it
delivered 13w, nasty clicks appeared about 1 or 2 KHz off the transmission
frequency.  I was afraid that it would be too easy to do this in the heat of a
contest.

2) The output filter toroids appeared to have been heated a bit.  Maybe I'm
imagining things...

3) The power output and swr indications were incorrect, and

4) I was afraid to use the KAT2.

So I'm back to the normal 15 watts on 160-15, and 13w on 12-10.  I guess I'll
wait for the KPA100. 

73,
Vic, K2VCO
Fresno CA

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