No, FT-8 is a weak signal mode.  That is not the same as a low power mode. 

Bob, K4TAX


Sent from my iPhone

> On Jul 17, 2018, at 9:15 AM, turnbull <[email protected]> wrote:
> 
> I thought FT8 was a low power mode.   Am I wrong?   I am not referring to Fox 
> Hound mode.
> 73 DOUG EI2CN
> 
> 
> Sent from my Samsung Galaxy smartphone.
> -------- Original message --------From: Michael Blake via Elecraft 
> <[email protected]> Date: 17/07/2018  14:12  (GMT+00:00) To: Nr4c 
> <[email protected]> Cc: Elecraft Reflector <[email protected]>, ANDY 
> DURBIN <[email protected]> Subject: Re: [Elecraft] KPA500 thermal clicks 
> While possibly my imagination, after a few months of use I loosened all of 
> the Z bracket to heatsink screws and side panel to heatsink screws and then 
> retightened all of them plus the top cover to Z bracket screws.  That seemed 
> to reduce the clicking.
> 
> Very 73 - Mike - K9JRI
> 
> 
> 
> 
>> On Jul 17, 2018, at 9:05 AM, Nr4c <[email protected]> wrote:
>> 
>> “Clicks” caused by the “Z” bracket are well documented and normal. 
>> Personally, I don’t find this “intolerable” or even slightly annoying. My 
>> wall clock “ticks” every second.  
>> 
>> Sent from my iPhone
>> ...nr4c. bill
>> 
>> 
>>> On Jul 17, 2018, at 7:56 AM, ANDY DURBIN <[email protected]> wrote:
>>> 
>>> The clicking of my KPA500 is almost intolerable and I'd like to know if 
>>> what I'm experiencing is typical.
>>> 
>>> 
>>> In an FT8 TX/RX cycle  with output power 126 W my KPA500 clicks 7-8 times 
>>> during 15 second transmit and 7-8 times during 15 second receive.  In these 
>>> TX/RX cycles my logger shows the finals temperature swings between 57 deg C 
>>> and 63 deg C.   During  this test the KPA500 was seeing an SWR of 1.02:1  
>>> and calculated PA dissipation was 307 W.
>>> 
>>> 
>>> I don't think this temperature swing is likely to cause the heat sink to 
>>> expand and contract significantly.  The thermal mass of the heat sink is 
>>> quite large and the heating and cooling periods are short.    The first 
>>> click happens almost as soon as the KPA500 is keyed.
>>> 
>>> 
>>> I think it is possible that the clicks are caused by expansion and 
>>> contraction  of the finals at their mounting points.   Is that likely and, 
>>> if so, why would it be considered normal?
>>> 
>>> 
>>> 73,
>>> 
>>> Andy k3wyc
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