[Elecraft] KPA500 thermal clicks

[Michael Blake]

FT8 is a weak signal mode.  That does not always equate to low power.  I have seen many instances on 6M where 400 watts resulted in a -15 signal report from the far end.

Many of the K1JT modes started with moon bounce where it often took 1500 watts to get a weak signal back.

Very 73 - Mike - K9JRI







> On Jul 17, 2018, at 10:15 AM, turnbull <turnbull at net1.ie> 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 <elecraft at mailman.qth.net>
> Date: 17/07/2018 14:12 (GMT+00:00)
> To: Nr4c <nr4c at widomaker.com>
> Cc: Elecraft Reflector <elecraft at mailman.qth.net>, ANDY DURBIN <a.durbin at msn.com>
> 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 <nr4c at widomaker.com> 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 <a.durbin at msn.com> 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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