Dan Koellen AI6XG
QRP Tube: High Voltage DC to DC Supply Evaluation
The high voltage supply for the vacuum tube transmitter needs to be low noise in the 40 meter band, efficient for battery operation and...
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Dan Koellen AI6XG
May 2, 20236 min read
QRP Tube: T/R Switch and QCX Interface and Modification
A Modified QCX and TR Switch for Vacuum Tube SOTA transmitter
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Dan Koellen AI6XG
May 2, 202315 min read
QRP Tube: Single Tube SOTA Transmitter
A single tube transmitter is developed for portable and Summits on the Air (SOTA) use. The SOTA transmitter had to be relatively...
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Dan Koellen AI6XG
May 2, 20235 min read
QRP Tube: Vacuum Tube, Battery, Lightweight, Compact, Portable: Can They Coexist?
Using vacuum tube equipment for SOTA activations? Why not! A portable battery operated vacuum tube transmitter is part of a SOTA system.
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Dan Koellen AI6XG
Jan 25, 20212 min read
The Digi-Disco, a 1970's Light Controller
This is a light system that I designed and built in 1978 to control large flood lights of different colors, synchronized to disco music...
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Dan Koellen AI6XG
Jan 25, 20211 min read
Heathkit IT-28 Capacitor Checker
After building the Pico C-Super capacitor tester that was published in Elektor Magazine I decided to revive an old Heathkit IT-28...
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