K2 output power on 10 meters

[Mike and Alicia Fanning]

Hi all,
I have been tweaking on my K2 for the last several days trying to get  
the transmit power up to snuff on 10 meters.  Right now, the best I  
can squeeze out is about 8.5 Watts.  I'm in pretty good shape on 12  
meters, about 10 Watts there, with max output of 14 Watts on 40m.  I  
have rewound and elevated T2, adjusted the turns spacing on the low  
pass filter toroids L21 and L22, and re-peaked the bandpass filters.  
8.5 Watts is as good as I can get.  Is this typical for a K2?  Is  
there something else I need to be looking at?

Thanks in advance for any suggestions.

73,
Mike, K4GU
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[Johnny Siu]

U are more or less there.
73 Johnny vr2xmc

Sent from my  iPhone 4

Mike and Alicia Fanning <[hidden email]> 於 2010年12月31日 下午12:36 寫道：

> Hi all,
> I have been tweaking on my K2 for the last several days trying to get  
> the transmit power up to snuff on 10 meters.  Right now, the best I  
> can squeeze out is about 8.5 Watts.  I'm in pretty good shape on 12  
> meters, about 10 Watts there, with max output of 14 Watts on 40m.  I  
> have rewound and elevated T2, adjusted the turns spacing on the low  
> pass filter toroids L21 and L22, and re-peaked the bandpass filters.  
> 8.5 Watts is as good as I can get.  Is this typical for a K2?  Is  
> there something else I need to be looking at?
>
> Thanks in advance for any suggestions.
>
> 73,
> Mike, K4GU
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html

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[Don Wilhelm-4]

  Mike,

The K2 maximum output power on 10 meters varies due to component
tolerances and care taken during construction.  Since you have
apparently done the normal things to improve it, and the power is still
low, it may be time to consider component tolerances - primarily for the
Q5 and Q6 stages.

One easy way to bring up the 10 meter output power is to change Q6 to a
transistor that typically has better high frequency performance.  The
2SC2166 that is being shipped with new K2 kits seems to produce better
output on 10 meters than some older K2s that I have worked on - I guess
this is tolerance drift over time, but that is only a guess.

Another way to increase the 10 meter output power is to change Q6 to a
2SC5739 which has better high frequency performance specification than
the 2SC2166.  If you do make this change, also change the value of R46
from 270 ohms to 330 ohms to keep the Q6 transistor at a cooler temperature.

73,
Don W3FPR

On 12/30/2010 11:36 PM, Mike and Alicia Fanning wrote:

> Hi all,
> I have been tweaking on my K2 for the last several days trying to get
> the transmit power up to snuff on 10 meters.  Right now, the best I
> can squeeze out is about 8.5 Watts.  I'm in pretty good shape on 12
> meters, about 10 Watts there, with max output of 14 Watts on 40m.  I
> have rewound and elevated T2, adjusted the turns spacing on the low
> pass filter toroids L21 and L22, and re-peaked the bandpass filters.
> 8.5 Watts is as good as I can get.  Is this typical for a K2?  Is
> there something else I need to be looking at?
>
> Thanks in advance for any suggestions.
>
> 73,
> Mike, K4GU
>

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[Bill Coleman-2]

On Dec 30, 2010, at 11:36 PM, Mike and Alicia Fanning wrote:

> I have been tweaking on my K2 for the last several days trying to get  
> the transmit power up to snuff on 10 meters.  Right now, the best I  
> can squeeze out is about 8.5 Watts.  I'm in pretty good shape on 12  
> meters, about 10 Watts there, with max output of 14 Watts on 40m.  I  
> have rewound and elevated T2, adjusted the turns spacing on the low  
> pass filter toroids L21 and L22, and re-peaked the bandpass filters.  
> 8.5 Watts is as good as I can get.  Is this typical for a K2?  Is  
> there something else I need to be looking at?

Not typical. You should be able to get 10w out.

I had limited output on 10m until I elevated T2 and re-peaked, and then didn't have a problem.

Is there any chance you may have fried one of the output transistors?

Bill Coleman, AA4LR, PP-ASEL        Mail: [hidden email]
Web: http://boringhamradiopart.blogspot.com
Quote: "Not within a thousand years will man ever fly!"
            -- Wilbur Wright, 1901

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