Re: [Elecraft] KX3 Heatsink discussion
Hi Jan, Elecraft designed the KX twins to run with maximum efficiency, so up to 10 watts, it is the more efficient PA in the KX3 which supplies the output power with the KXPA100 in bypass, and when more than 10 watts is dialed in the KXPA100 is enabled, and the KX3 throttles back to make the KXPA100 output whatever is desired. Cheers & 73, Howie - WA4PSC __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@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 arch...@mail-archive.com
Re: [Elecraft] KX3 Heatsink discussion
OH ~ I think we all understand that the word "heat-sink" implies that it might/will get warm :-) BUT ~ I originally asked about the "heating" of the KX3 when driving the KXPA100 at 20W SO ~ I experimented this morning with adjusting the power OUT of the KX3 while driving the KXPA100 amplifier. With rotation of the Power knob on the KX3, it climbs to 10W [as measured at the Output of the KX3] and with further rotation of the knob, it drops to less than 2W for ~ 40W out from the Amplifier and about 4W yields ~ 100W from the Amp. THUS ~ why should the KX3 heat-up when driving an amplifier Cheers, Jan K1ND __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@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 arch...@mail-archive.com
[Elecraft] KX3 Heatsink discussion
Sorry of this appears twice, I got a bounce on the first submission: The Pro Audio Engineering Kx32 Heatsink has more surface area than any other commercially available KX3 heatsink. Regarding mass, more is not necessarily better. If you take two heatsinks with the same surface area, on the initial key-down the one with more mass gives a longer initial warmup time. Unfortunately it also retains heat longer, meaning on the subsequent transmit cycles, it still retains heat from the previous cycle. We strove to minimize the mass of our heatsinks, the limitation ended up being rigidity and resistance of the fins to damage. The limitation on convective heatsink efficiency is not the thermal conductivity of aluminum, it is surface area. Our tests show very little thermal Δ (delta if your browser is ASCII only!) across the area of any given heatsink of almost any convective design. This is because the limitation is dissipation due to convection. If you model the thermal path as a series string of resistances, the aluminum is very low resistance and the surface to air resistance is very high. For more information visit our website! Cheers & 73, Howie Pro Audio Engineering __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@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 arch...@mail-archive.com
Re: [Elecraft] KX3 Heatsink discussion
Actually, that’s 63 C at the PA device location on the PC board. The outside surface of the heat sink itself is quite a bit lower in temperature. Wayne N6KR > On Aug 6, 2017, at 11:39 AM, Wayne Burdick wrote: > > The KX3 and KX2 max heat sink temperature is 63 C. At that point power is > automatically dropped to 5 W. If it reaches the max temp again, transmit is > exited. > > Wayne > N6KR > > > >> On Aug 6, 2017, at 10:27 AM, Jim Brown wrote: >> >> A well designed output stage SHOULD be hot to the touch. The temperature >> component of protection in Elecraft output stages seems to kick in when the >> internal temperature approaches 70 deg C. You can see this, for example, by >> watching temperature in the KPA500 and listening to fan speed. The function >> of the heat sink is to act as a conductor between the semiconductor >> junctions and the surrounding environment, and increased mass acts as a sort >> of buffer. >> >> 73, Jim K9YC >> >> On 8/5/2017 2:53 PM, Jan wrote: >>> ""I've been doing a lot of FT-8 using my KX3 and my KXPA100 at 20 watts, >>> and have noticed that the KX3 is heating up quite a bit and is almost >>> hot to the touch"" >>> >>> Why should the KX3 be heating up, when the AMP is running only 20W ? >>> Is the KX3 "drive" not backed-down at this level ?? HELP >> >> >> __ >> Elecraft mailing list >> Home: http://mailman.qth.net/mailman/listinfo/elecraft >> Help: http://mailman.qth.net/mmfaq.htm >> Post: mailto:Elecraft@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 n...@elecraft.com > __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@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 arch...@mail-archive.com
Re: [Elecraft] KX3 Heatsink discussion
The KX3 and KX2 max heat sink temperature is 63 C. At that point power is automatically dropped to 5 W. If it reaches the max temp again, transmit is exited. Wayne N6KR > On Aug 6, 2017, at 10:27 AM, Jim Brown wrote: > > A well designed output stage SHOULD be hot to the touch. The temperature > component of protection in Elecraft output stages seems to kick in when the > internal temperature approaches 70 deg C. You can see this, for example, by > watching temperature in the KPA500 and listening to fan speed. The function > of the heat sink is to act as a conductor between the semiconductor junctions > and the surrounding environment, and increased mass acts as a sort of buffer. > > 73, Jim K9YC > > On 8/5/2017 2:53 PM, Jan wrote: >> ""I've been doing a lot of FT-8 using my KX3 and my KXPA100 at 20 watts, >> and have noticed that the KX3 is heating up quite a bit and is almost >> hot to the touch"" >> >> Why should the KX3 be heating up, when the AMP is running only 20W ? >> Is the KX3 "drive" not backed-down at this level ?? HELP > > > __ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:Elecraft@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 n...@elecraft.com __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@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 arch...@mail-archive.com
Re: [Elecraft] KX3 Heatsink discussion
A well designed output stage SHOULD be hot to the touch. The temperature component of protection in Elecraft output stages seems to kick in when the internal temperature approaches 70 deg C. You can see this, for example, by watching temperature in the KPA500 and listening to fan speed. The function of the heat sink is to act as a conductor between the semiconductor junctions and the surrounding environment, and increased mass acts as a sort of buffer. 73, Jim K9YC On 8/5/2017 2:53 PM, Jan wrote: ""I've been doing a lot of FT-8 using my KX3 and my KXPA100 at 20 watts, and have noticed that the KX3 is heating up quite a bit and is almost hot to the touch"" Why should the KX3 be heating up, when the AMP is running only 20W ? Is the KX3 "drive" not backed-down at this level ?? HELP __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@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 arch...@mail-archive.com
[Elecraft] KX3 Heatsink discussion
I'm puzzled by the comment posted yesterday: by Jim W7JR ""I've been doing a lot of FT-8 using my KX3 and my KXPA100 at 20 watts, and have noticed that the KX3 is heating up quite a bit and is almost hot to the touch"" Why should the KX3 be heating up, when the AMP is running only 20W ? Is the KX3 "drive" not backed-down at this level ?? HELP Cheers, Jan K1ND __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@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 arch...@mail-archive.com
