[Elecraft] Upper limits of KPA500?

Mon May 4 09:53:37 EDT 2020

Nowadays manufacturers use 'ICAS'. One even specs their amp for '100% 
duty cycle ICAS'. ICAS=Intermittent Continuous Amateur Service'. 
Gobbledegook!

100% duty cycle is what Alpha used to say.... brick on the key forever. 
FT8, JT65 are 50% duty cycle modes. SSB is about 33% during transmit, CW 
is 50% during transmit. Duty cycle has no time limit.

-de John NI0K

Dave Cole wrote on 5/4/2020 8:39 AM:
> 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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