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K6AFS USA flag USA

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QSL image for K6AFS

Started in 1971 as DU1AFS in Manila with a homebrew 120-watt CW and AM transmitter using a pair of 6L6GC finals to work 40M and 20M. Receiver was an Ecophone EC-1A with an outboard preselector then later changed to a Hallicrafters SX42. I enjoyed so much dx with this setup. I built another homebrew transmitter with a pair of 6KD6 sweep tubes for more PEP power. This inspired me to finish an Electrical Engineering degree from University of the Philippines. In the 80's I worked in the broadcast industry then moved to the vhf/uhf radio business making repeaters and setting them up for civilian and goverment agencies. In the 90's I moved into designing circuits for commercial electronics and cellular. After more than 40 yrs in Electronics, I like restoring and operating old radios.

Homebrew all-mode HF transmitter with a pair of 6KD6 sweep tube finals (above) from 1974.

I've been using a 1950's vintage Collins KWS-1 as my daily transmitter for almost 20yrs now. It likes to drift a few hundred hz over 2 or 3 hours. This was state of the art in 1956 but nowadays people get very concerned when they hear someone drift that much. Therefore I decided to upgrade its frequency stability to be at least equal to modern rigs. I designed a homebrew DDS frequency control board (above) for the KWS-1 using an AD9851 chip with OCXO reference. Also added an AFC stabilizer to the VFO tied to the same OCXO reference (below). The KWS-1 still works just like before and the modifications are completely transparent. The OCXO now makes the 1956 transmitter extremely stable at 0.1ppm.

952532 Last modified: 2014-05-24 16:37:38, 2006 bytes

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