http://elecraft.85.s1.nabble.com/K2-Heat-On-Digital-Modes-tp5572168p5573363.html
RTTY filter set in the secondary menu. That gives you a set of filters
waterfall display and switch to the more narrow filters. With PSK the
> Don,
>
> Again, thanks for quick reply.
>
> Guess I know what I'll be doing this weekend. That's okay, I was going to open
> it up anyway to adjust the SSB filters to get narrow filtering for use in
> digital modes.
>
> Jon
> KB1QBZ
>
>
>
> ________________________________
> From: Don Wilhelm<
[hidden email]>
> To: Jon Perelstein<
[hidden email]>
> Cc: elecraft reflector<
[hidden email]>
> Sent: Sun, September 26, 2010 7:12:49 PM
> Subject: Re: [Elecraft] K2: Heat On Digital Modes
>
> Jon,
>
> Your quick tests are sufficient to negate my initial suspicion.
>
> I would say your next step is to re-do the KPA100 bias adjustment. If you
> have the bias set too high, the PA transistors will heat more than normal.
>
> Meter the current into the KPA100 - put the K2 into CW test (hold the VOX
> button) and make sure the "C" indicator in the display is blinking - connect
> a dummy load to the KPA100 'just in case'. Set power to greater than 11
> watts. The current draw will be in the vicinity of 500 ma. Whatever your
> external ammeter says, add 400 ma to that - this is your target value.
> The hold TUNE, and look at the ammeter - If it is a digital meter, wait
> until the 2nd reading (blink) because the first value shown may be too low
> due to the relative timing of the meter vs the time you pushed the TUNE
> button.
> The current will go up the longer you remain in TUNE, so obtain the reading
> and exit tune - adjust the KPA100 bias up or down a bit and try again. Once
> you have hit your target value, you are done - be sure to remove the ammeter
> from the power line.
>
> While you have the shield off the KPA100, you may want to check the balance
> on the wattmeter (C1 adjustment) and the power calibration with reference to
> a wattmeter that you are willing to trust.
>
> You should be ale to operate the KPA100 at 35 watts continuously without it
> getting too hot to touch - yes it will get quite warm, but not too hot to
> touch unless you have more sensitive fingers than average. RTTY can be
> considered continuous, PSK31 should be OK up to 50 watts since the PSK idle
> has a shorter duty cycle.
>
> If the bias and wattmeter are correct, and you still feel it is getting
> warmer than you would like, you might want to try a supplemental fan - find
> one from a defunct computer, and run it with a resistor in series to slow it
> down so the noise does not irritate. It can be placed on top of the heat
> sink, moving air away and will be quite effective. See Tom Hammond's
> website www.n0ss.net for his implementation.
>
> 73,
> Don W3FPR
>
> On 9/26/2010 6:49 PM, Jon Perelstein wrote:
> Don
>>
>> Thanks for the quick reply. Fortunately, it appears that uncontrolled
>> power output is not the problem.
>>
>>
>> And yes, it is a K2/100.
>>
>>
>> I connected the rig to an MFJ-941E Versatuner II and connected the
>> Versatuner to my antenna. I tuned to a 1.1:1 SWR using the Versatuner
>> and then measured forward power on CW key down at various power
>> settings. The forward power transitioned smoothly from just under 20
>> watts with the rig set to 20 watts to just over 90 watts with the rig
>> set to 100 watts. I probably need to do some calibration, but it
>> appears that the power control is working.
>>
>>
>> I also tried it with PSK and Olivia transmissions and the Versatuner
>> was showing around 25 watts when I had 25 watts set on the K2's power
>> control. I upped the K2s power control to 40 watts and saw an
>> increase in forward power on the Versatuner to about 35 watts or so.
>>
>>
>> I can get my hands on a real wattmeter in the next few days if you
>> think it necessary, but these tests would imply that I am not
>> experiencing uncontrolled power.
>>
>>
>> Jon
>> KB1QBZ
>>
>>
>>
>>
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