Over the 4th of July vacation, I built a zero-beat detector for my KX1. At first I was using a data book design, but I found this one by KR5L on N0SS's site and just built his on perfboard.
http://home.earthlink.net/~n0ss/kr5l_cw_tuning_ind.pdf I was visiting my sister (ex WN5UOE) in San Luis Obispo, CA and looked for a parts store where I might find the 567; oddly enough, Mid State Electronics (http://tinyurl.com/33m7s) was within walking distance of where we were staying! It's a great store, and if you are ever in central California, it's worth a visit. They had lots of great parts, grab bags, mixer and FM chips, APP connectors, tools, PC etching supplies, tens of thousands of through-hole parts, hobby kits, you name it. Anyway, I wired up a couple of stereo headphone jacks in parallel, and tapped one channel to the PLL circuit's input. I used a PSK program waterfall to measure the PLL's reference oscillator and set it to 600 Hz (actually I measured its 5th harmonic ;-). If I were to go whole hog, I'd probably put in switched jacks to control the power, and maybe an optional pad for mixing both output channels from the KX1 to boost the signal for weak stations. With a comfortable listening volume for a CW signal, the LED is on for +/10Hz, but it's easily centered, or you can turn the audio gain down and get it to illuminate for only one 10Hz segment. With really low signals it doesn't lock. I built an LM386 mono amp to go with it, which I thought about using for low signals and also to drive an external speaker, but I couldn't fit all three (PLL circuit, 386 and speaker) in the plastic case so I figured I'd house the amplified speaker separately. The zero beat detector seems to draw about 20mA from a 9V battery through a 6.2V Zener, which is roughly half the draw of the entire KX1. Jerry KR5L said he was experimenting with a low-power PLL... I probably won't be taking this everywhere I take my KX1, but I might throw it in a suitcase. Leigh WA5ZNU _______________________________________________ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
