[Elecraft] K2 Power Level

[Lyn Norstad]

Interesting point, Don.

I never thought of the "finger test" for that purpose, but the "Threshold of
Pain" is normally considered to be 42C (or 107F).  My KPA500 reaches that
temp after about 8 seconds of 40 meter carrier with a drive level of 18
watts and an output level of about 350 watts. (Normal 'power off temp' runs
about 37C).

The average person can touch a 140F surface for 5 seconds without sustaining
irreversible burn damage.

Such a simple, basic thing to know ... but who does?

73
Lyn, W0LEN


-----Original Message-----
From: elecraft-bounces at mailman.qth.net
[mailto:elecraft-bounces at mailman.qth.net] On Behalf Of Don Wilhelm
Sent: Monday, August 16, 2021 1:55 PM
To: elecraft at mailman.qth.net
Subject: Re: [Elecraft] K2 Power Level

All,

I was reminded that I should have added that CW and SSB are low duty 
cycle modes while FT8 and several other data modes are high duty cycle 
and will produce more heat.

The 'finger test' I mentioned is suitable for any mode.

73,
Don W3FPR
----------------------------------------------------------------------------
------------------------------
Aaron,

I cannot give you a specific answer, but go by the heat.
I would suggest you first try 5 watts, and operate at that level for a 
while (I suggest 10 minutes).
Then check the heatsink temperature - if you can hold your fingers on it 
for longer than 5 minutes, then all is well.
Increase the power by about 3 watts and try again.
When the heat gets too much to comfortably hold your fingers on the 
heatsink (next to the PA transistors), then you have exceeded the 
maximum power which you should use for transmit.

The generalized answer is that you should consider those modes as 
continuous duty and use 1/2 the normal full power output, but I suggest 
doing the test I referred to as a specific power limit for your 
particular K2.

73,
Don W3FPR

On 8/13/2021 3:38 PM, Aaron K5ATG wrote:
> What is the recommended highest power level for a QRP Elecraft K2 to
> operate on digital modes like FT8, JT65 etc, without blowing the PA's?
>


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