[Elecraft] Upper limits of KPA500?

Mon May 4 11:12:51 EDT 2020

The FCC document on estimating RF exposure lists “duty factor” for various modes. That is average power compared to peak while transmitting.

SSB 20%
SSB with heavy speech processing 50%
FM, FSK, RTTY, carrier 100%
CW 40%

Separately, they talk about on/off periods, the average time spent transmitting during a 6 minute or 30 minute period. See pages 14 and 15.

https://transition.fcc.gov/bureaus/oet/info/documents/bulletins/oet65/oet65b.pdf

wunder
K6WRU
Walter Underwood
CM87wj
http://observer.wunderwood.org/ (my blog)

> On May 4, 2020, at 7:40 AM, Randy Moore <wrmoore47 at gmail.com> wrote:
> 
> ICAS means Intermittent Commercial and Amateur Service.
> 
> From the RCA Transmitting Tube Manual:
> 
> Intermittent Commercial and Amateur Service (ICAS) covers aplications in which high tube output is a more important consideration than long tube life. The term "Intermittent Commercial" in this title applies to types of services in which the operating or "on" periods do not exceed 5 minutes each, and are followed by "off" or stand-by periods of the same or greater duration. The term "Amateur Service" covers other applications where operation is of an infrequent or highly intermittent nature, as well as the use of tubes in "amateur" transmitters. ICAS ratings generally are considerably higher than CCS ratings. Although the ability of a tube to produce greater output power is usually accompanied by a reduction in tube life, the equipment designer may decide that a small tube operated at its ICAS ratings meets his requirements better than a larger tube operated within CCS ratings.
> 
>> On May 4, 2020, at 8:55 AM, John Simmons <jasimmons at pinewooddata.com> wrote:
>> 
>> 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
>>>>>>> ______________________________________________________________
>>>>>>> Elecraft mailing list
>>>>>>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
>>>>>>> Help: http://mailman.qth.net/mmfaq.htm
>>>>>>> Post: mailto:Elecraft at mailman.qth.net
>>>>>>> 
>>>>>>> This list hosted by: http://www.qsl.net
>>>>>>> Please help support this email list: http://www.qsl.net/donate.html
>>>>>>> Message delivered to rick.nk7i at gmail.com
>>>>>> ______________________________________________________________
>>>>>> Elecraft mailing list
>>>>>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
>>>>>> Help: http://mailman.qth.net/mmfaq.htm
>>>>>> Post: mailto:Elecraft at mailman.qth.net
>>>>>> 
>>>>>> This list hosted by: http://www.qsl.net
>>>>>> Please help support this email list: http://www.qsl.net/donate.html
>>>>>> Message delivered to dave at nk7z.net
>>>>> ______________________________________________________________
>>>>> Elecraft mailing list
>>>>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
>>>>> Help: http://mailman.qth.net/mmfaq.htm
>>>>> Post: mailto:Elecraft at mailman.qth.net
>>>>> 
>>>>> This list hosted by: http://www.qsl.net
>>>>> Please help support this email list: http://www.qsl.net/donate.html
>>>>> Message delivered to rick.nk7i at gmail.com 
>>>> ______________________________________________________________
>>>> Elecraft mailing list
>>>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
>>>> Help: http://mailman.qth.net/mmfaq.htm
>>>> Post: mailto:Elecraft at mailman.qth.net
>>>> 
>>>> This list hosted by: http://www.qsl.net
>>>> Please help support this email list: http://www.qsl.net/donate.html
>>>> Message delivered to dave at nk7z.net
>>> ______________________________________________________________
>>> Elecraft mailing list
>>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
>>> Help: http://mailman.qth.net/mmfaq.htm
>>> Post: mailto:Elecraft at mailman.qth.net
>>> 
>>> This list hosted by: http://www.qsl.net
>>> Please help support this email list: http://www.qsl.net/donate.html
>>> Message delivered to jasimmons at pinewooddata.com 
>> 
>> ______________________________________________________________
>> Elecraft mailing list
>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
>> Help: http://mailman.qth.net/mmfaq.htm
>> Post: mailto:Elecraft at mailman.qth.net
>> 
>> This list hosted by: http://www.qsl.net
>> Please help support this email list: http://www.qsl.net/donate.html
>> Message delivered to wrmoore47 at gmail.com
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:Elecraft at mailman.qth.net
> 
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to wunder at wunderwood.org