Because it’s weak signal at the receiving end; you use what power it takes to
succeed in making the contact, up to the legal limit.
On 160M, 1500 watts out is common.
Rick NK7I
Smell Czech corruptions are inevitable
> On Apr 4, 2020, at 9:02 PM, brianchapnick <brianchapn...@rogers.com> wrote:
>
> This discussion fascinates me only in that I wonder why you are using so
> much power for weak signal modes? 5 or 10 watts should be plenty even with a
> compromised antenna and poor band conditions......or am I missing
> somthing.Brian VE3GMZ Sent from my Samsung Galaxy smartphone.
> -------- Original message --------From: Bob McGraw K4TAX
> <rmcg...@blomand.net> Date: 2020-04-04 8:19 p.m. (GMT-05:00) To:
> elecraft@mailman.qth.net Subject: Re: [Elecraft] Max power for JT9 with K3S
> 100? Frank et al;Just quoted what is in the K3S manual. No interpretation
> provided. I agree that 100 watts key down is a lot for a SSB amplifier
> running in CW mode. To me that says 100 watts for 10 minutes and then RX
> for 10 minutes. Otherwise equal TX and RX times. Who does that?And if one
> is running "100 watts" then running CW or SSB for 10 minutes might be the
> limit. Just speculation. On AM I might talk for 10 minutes but that is at
> 25% rated power output for carrier, yet it is 100 watts PEP. The 60 C is MY
> guideline. The KPA3A will shut down about 85 C or so.On 6M I run my KPA500 at
> about 300 to 400 watts. The K3S is running about 25 to 30 watts on 6M. At
> this point I'm watching the KPA500 temperature.There is NO DX worth blowing a
> PA either in the K3S or the KPA500. But I know guys that will blow things
> up, pushing things to the max and beyond trying to work that DX station. I
> say bah humbug to that!I just pay attention to the PA temp, specially when
> running digital modes. Likewise for the KPA500.73Bob, K4TAXOn 4/4/2020 3:41
> PM, Frank O'Donnell wrote:> 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>>
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