[Elecraft] Max power for JT9 with K3S 100?

[Frank O'Donnell]

Thanks for the replies.

I've enabled the PA temp display (currently showing 22C right after 
power-up but before transmitting), and will keep an eye on that.

Bob, I noticed that line in the K3S manual about the CW/SSB duty cycle. 
Does "100% - 10 min, 100 W key-down" mean that if you key down without 
stop in CW mode it can go 10 minutes at 100 watts? That seems like an 
awful lot.

Where do the recommended TPO's for 6 meters, the 50% value for JT9, and 
the 60C guideline for the PA temp come from?

Thanks again,

Frank K6FOD


On 4/4/20 6:22 AM, John Simmons wrote:
> Fred Cady's book:
>
> "There are four fans speeds that turn on at different temperatures."
> "If the temperature reaches 84 degrees C the KPA3 will be bypassed 
> until the temperature falls to stop any damage as a last-ditch backup 
> measure to protect your expensive power transistors from the excess 
> heat."
>
> -de John NI0K
>
>
> Bob McGraw K4TAX wrote on 4/3/2020 6:39 PM:
>> Frank:
>>
>> The duty cycle for the transmitter, as stated in the manual, is;  CW 
>> and SSB modes, 100% - 10 min, 100 W key-down at 25C ambient.   Do 
>> note that 6M has reduce power values of 85 watts {51 -52 MHz} or 70 
>> watts {52 - 54 MHz}
>>
>> The duty cycle for JT-9, 1 minute transmit, 1 minute receive would be 
>> 50%.   I frequently run 100 watts on WSJT-X FT-8 with no issues.  
>> Just pay attention to PA temperature.  It should be 60 C or less.   
>> Also this is with FANS in the automatic mode.
>>
>> 73
>>
>> Bob, K4TAX
>>
>>
>> On 4/3/2020 4:18 PM, Frank O'Donnell wrote:
>>> I've been using JT9 mode on 630m this winter with my K3S outputting 
>>> to an external class D amp.
>>>
>>> Now I'm interested in trying some JT9 QSOs with some people 
>>> currently operating on 160m. For me this would mean outputting 
>>> directly from the K3S (with internal tuner) to the antenna.
>>>
>>> Given the 1-minute cycle time for JT9, are there recommendations 
>>> (official from Elecraft, or otherwise) on maximum power to use in a 
>>> situation like this? And/or, is the answer dependent on the SWR I 
>>> can achieve with the antenna?
>>>
>>> Thanks and 73,
>>>
>>> Frank K6FOD