[Elecraft] Upper limits of KPA500?

Mon May 4 14:11:27 EDT 2020

Thank you Jack...  I had not seen that.  That answers the question.

73, and thanks,
Dave (NK7Z)
https://www.nk7z.net
ARRL Volunteer Examiner
ARRL Technical Specialist
ARRL Asst. Director, NW Division, Technical Resources

On 5/4/20 9:11 AM, Jack Brindle wrote:
>  From the KPA500 manual, Rev E1, page 41 Specifications:
> 
> Duty Cycle at 500 Watts10 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 
>> <mailto: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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> 