I have found that with even a freshly charged 7Ah battery that the power folds back, on some bands especially, even if the internal atu has found a good match. However, in almost all cases setting the power output to 8W rather than initially 10W it doesn't happen as much, at least not until the battery voltage has fallen well below 12V.
73 Stephen G4SJP On Tuesday, 6 August 2013, Dominic Baines wrote: > Arno, > > Sure someone from Elecraft will respond with a technical > explanation...sounds a bit like default behaviour to me and also shows > there is a difference in the battery and the internal PA voltage and you > are maybe close to the fold back voltage. > > If the supply voltage drops below 12V (I use 7AH SLA batteries so see this > often) then it can be lower at the PA internally (c11V + a bit) when it is > the KX3 folds back to 5W, no real warning it just does it. I found it a bit > annoying when I knew mine was running hot but then the KX3 was designed > with battery /P operation in mind (I assume). The KX3 does the same thing > to protect the KX3 if the PA gets too hot (you could try this, not sure it > will damage the KX3 so be warned, I did this when I fitted a heatsink to > reduce the issue... set power out to 10W, key down or send dah dah > constantly with a keyer for a few minutes into a dummy load (not on air!) > to make it fun do this in bright sun and watch the PA temp rise and rise > and the rear metal panel gets hot, eventually the temperature will exceed > what is 'safe' and the power will reduce, same thing happens for excess > current say if a PA transistor is failing or an antenna impedance/VSWR > changes there are multiple reasons and a few other situations all are > designed to protect the KX3. > > You could monitor the KX3 reported PA temperature and the KX3 reported > voltage and see when it happens so you know when to adjust the power out > level yourself or know when it is likely to happen. > > I have a really nice light weight /P switch mode mains power supply it > provides 12.2V (was for a CCTV camera) the KX3 will never exceed 8W out > with it on CW, if you set 10W it folds back immediately to 5W. > > 72 > > Dom > M1KTA > On 05/08/13 22:49, Arno Dienhart wrote: > >> So I had set up in the park, with a charged 12V 17Ah battery connected. It >> was a hot day but I was in the shade. >> >> >> Every time I set power level to 10W and keyed the TX, it reverted back to >> 5W >> instantly. Why? >> >> >> The Volt meter showed 12.3 V at RX and dropped to 11.7V at TX. Was that >> the >> reason (getting below 12V)? >> >> Was the PA getting too hot? It never went below 5W. >> >> >> Thanks for any tips, >> >> >> 73, >> >> >> Arno >> > > ______________________________**______________________________**__ > Elecraft mailing list > Home: > http://mailman.qth.net/**mailman/listinfo/elecraft<http://mailman.qth.net/mailman/listinfo/elecraft> > Help: http://mailman.qth.net/mmfaq.**htm<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 > -- Sent from Gmail Mobile ______________________________________________________________ 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
