RF OUT: Don't forget that the output filters are fixed-tuned for the impedance expected when running 10 watts for decent efficiency and proper suppression of the harmonics.
As a minimum you should re-design the output bandpass filters for each band to match the changed impedance load needed by the finals at the higher power level. And then there's the question of the ratings of the components in the T/R switch. And, if you work SSB or any digital modes using a sound card driving the K2 in SSB mode, the IMD levels go up as you go past 10 watts. Maybe I'm too conservative, but I tend to run equipment inside the red line specs. Maybe that's why I have experienced only one or two equipment failures in over half a century, Hi! AUDIO: I'm very surprised by the audio level issue. My K2 will "rattle the rafters" with the audio gain half way up on either the internal or an external speaker. I mean it's painfully loud! You might want to do some troubleshooting, starting with looking for a short circuit in the speaker wiring. IIRC, plugging in the speaker backwards will kill the audio level by grounding the "hot" audio lead. 73, Ron AC7AC -----Original Message----- From: elecraft-boun...@mailman.qth.net [mailto:elecraft-boun...@mailman.qth.net] On Behalf Of Vic K2VCO Sent: Thursday, September 26, 2013 9:28 AM To: elecraft@mailman.qth.net Subject: Re: [Elecraft] K2: maximizing RF output, upping audio output. Before the KPA100 came out I experimented with the K2 to see if I could get more output to drive an external amplifier. There IS a way, but I am sure there are lots of dangers involved. I will say that I did this for a month or so until I got my KPA100. I am not recommending it! The K2 has a closed-loop power control circuit. The MCU looks at the amount of power being produced and adjusts the drive to increase or decrease it until it matches the setting of the POWER control. So if you lie to the MCU and tell it that less power is coming out than actually is, it will increase the drive to try to make it reach the set point. I have a KAT2 so all I had to do was adjust the forward power pot to say that there was less output. I believe I got about 22 watts on 40 meters this way (less on other bands). Again, you are undoubtedly stressing things beyond design limits when you do this and bad things could happen. It might be better to get an external amplifier like the HF Packers use. On 9/26/2013 5:55 AM, Allan Taylor wrote: > I have a very early K2 that I use for field operations. It functions > as an emergency communication source for serious backcountry trips > (multi-day wilderness whitewater rafting, etc.). I am finding that a > power output of, say, 20W would be desirable as a compromise between > more reliable communication and battery usage. My K2 puts out about > 14W. Thus I ask the experts: has anyone revamped the TX RF stages > sufficient to put out > 20 -25W output? Yes, I know this amounts to only a dB or two. But it > can be the edge needed in very marginal conditions. > > Second issue. The K2 has always been on the low side for RX audio. > Being no longer a young buck, my hearing is not perfect any more. Is > there a known mod to add 5-10 dB to the audio chain without drastic > distortion? Presently I take along a Radio Shack headphone 3-way amp > that gives about that. It works fine but is yet another piece of gear > to bring along and doesn't feed the internal speaker. When I had a KX1 > (now sold) it had been modified to have a second audio amp chip put in > and it really helped. Has anyone done a similar thing for the K2? I am > not a EE by any means so would prefer to follow known modification > paths. > > Anyone? > -- Vic, K2VCO Fresno CA http://www.qsl.net/k2vco/ ______________________________________________________________ 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 ______________________________________________________________ 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
