[Elecraft] Upper limits of KPA500?

[Jack Brindle]

From the KPA500 manual, Rev E1, page 41 Specifications:
Duty Cycle at 500 Watts	 10 minutes key down / 5 minutes standby

Sometimes it is very worth while to read the manual. It gives me something to do when being stuck at home for so long gets me down.

73!
Jack, W6FB
 
> On May 4, 2020, at 6:39 AM, Dave Cole <dave at nk7z.net> wrote:
> 
> Hi Rick,
> 
> This brings up a point I have been unsure about for years...  Duty Cycle...  What constitutes 100%?  Over how long a time frame?
> 
> If I run JT65, (one minute on one minute off), and I use a timeframe of say 5 minutes, I buy it is 50% duty cycle.
> 
> But if I use a timeframe of one minute it is 100% Duty Cycle...
> 
> So when stating duty cycle it is important to spec the timeframe, as you did...  Is there an actual timeframe stated someplace as a standard?
> 
> I do like the way you stated it by the way...  With time to 'catch the breath'...
> 
> 73, and thanks,
> Dave (NK7Z)
> https://www.nk7z.net
> ARRL Volunteer Examiner
> ARRL Technical Specialist
> ARRL Asst. Director, NW Division, Technical Resources
> 
> On 5/3/20 8:53 PM, Rick Bates, NK7I wrote:
>> I didn't add the obvious, FT8 in that manner is a 50% duty cycle but with enough time to 'catch the breath'.
>> I remember back when it first came out, Wayne suggested to 'run it with all the LEDs lit' or something along that line but... it's capable of MUCH more than 500 watts and wisely better limited by firmware upgrades (in the early days I watched it put out almost 700, at which point I was far more cautious).  It's nice to know there is a certain amount of 'overhead'.
>> Rick NK7I
>> On 5/3/2020 8:23 PM, Dave Cole wrote:
>>> Hi Rick,
>>> That is how mine behaves as well, almost exactly like that... However, I will be running SSTV, and that is hard on the amp...  I need to do a bit more testing prior to that.
>>> 
>>> As someone else said upthread, half power is really tough on the amp...
>>> 
>>> 73, and thanks,
>>> Dave (NK7Z)
>>> https://www.nk7z.net
>>> ARRL Volunteer Examiner
>>> ARRL Technical Specialist
>>> ARRL Asst. Director, NW Division, Technical Resources
>>> 
>>> On 5/3/20 7:52 PM, Rick Bates, NK7I wrote:
>>>> I spent 15 minutes active on 20M FT8 this afternoon (some lurking).
>>>> 
>>>> At 530 watts output (on the display and utility) into a 1.13:1 antenna load (SteppIR) for a ten minute calling period (Mongolia then Oman), the temp rose to 66C; a few moments of elevated fan quickly brought that down to the low 60's between transmissions.
>>>> 
>>>> Ambient room temp 77F.  (Both calls succeeded.)
>>>> 
>>>> Rick NK7I
>>>> North Idaho
>>>> 
>>>> On 5/3/2020 7:42 PM, Andy Durbin wrote:
>>>>> "It is interesting to hear how others experience their KPA500s over various conditions."
>>>>> 
>>>>> I have over a years's worth of KPA500 data recorded but it takes some effort to run it through the Excel templates to make pretty plots.
>>>>> 
>>>>> My KPA500 temperatures are strongly influenced by ambient temperature.  Shack temperature is often over 30 deg C in the summer months and it's not at all unusual for my fan to run at level 3 in FT8 QSO.  I think I have only reached fan speed 5 twice and that was while running temperature tests not while operating.   I terminated those tests at fan speed 5 and didn't wish to push it any higher.
>>>>> 
>>>>> So many people seem to think reducing the output power will keep the temperature down.  It does not.   Half power is about the worst heat dissipation condition for the KPA500.
>>>>> 
>>>>> 73,
>>>>> Andy, k3wyc
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>> ______________________________________________________________
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