Dan Koellen AI6XG
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...
top of page
Making and Hacking
Dan Koellen AI6XG
- May 2
- 6 min
T/R Switch and QCX Interface and Modification
A Modified QCX and TR Switch for Vacuum Tube SOTA transmitter
44 views0 comments
Dan Koellen AI6XG
- May 2
- 14 min
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...
117 views0 comments
Dan Koellen AI6XG
- May 2
- 5 min
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.
863 views0 comments
Dan Koellen AI6XG
- Feb 28
- 5 min
All Wound Up About EFHW Transformer Winding
After successfully using an End Fed Half Wave (EFHW) antenna for SOTA, I decided to build a 10 to 80 meter EFHW antenna for my home...
907 views0 comments
Dan Koellen AI6XG
- Jun 17, 2022
- 5 min
Evaluating efficiency, transformer and mismatch losses in toroid transformers - some observations.
Two methods for transformer loss are evaluated. We learn that mismatch loss must be accounted for.
579 views0 comments
Dan Koellen AI6XG
- May 16, 2022
- 6 min
Reactive Component Measurement With the NanoVNA
Exploration of using the nanoVNA to measure inductance and capacitance at frequency of use.
1,047 views0 comments
Dan Koellen AI6XG
- Mar 2, 2022
- 11 min
Toroid Transformers - How Hot Will It Get?
There are a number of factors in choosing a toroid for a RF transformer. While one may model electrical performance, calculate predicted...
1,303 views0 comments
Dan Koellen AI6XG
- Jul 20, 2021
- 9 min
Electrostatic Discharge (ESD), Does it Matter for Makers and Hackers?
Electrostatic Discharge (ESD) is a subject that can inspire a lot of discussion, head shaking and some misunderstanding. ESD damaging...
610 views0 comments
Dan Koellen AI6XG
- Jun 16, 2021
- 13 min
Don't Fear the Smith Chart
Like many radio amateurs I was initially intimidated by the Smith chart. Transmission line and antenna theory, unfamiliar terms and...
1,046 views3 comments
Dan Koellen AI6XG
- Apr 25, 2021
- 9 min
How I Killed a Microcontroller
This blog outlines the steps taken to determine why a microcontroller no longer works, and the journey to find the damage on the chip.
236 views0 comments
Dan Koellen AI6XG
- Jan 25, 2021
- 2 min
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...
139 views1 comment
Dan Koellen AI6XG
- Nov 23, 2020
- 1 min
Wishing You a Very Random Christmas
Being the holiday season I decided to post this article from the December 2014 issue of Nuts & Volts magazine www.nutsvolts.com that I...
73 views0 comments
Dan Koellen AI6XG
- Jun 29, 2020
- 7 min
Big Font Clock Update: Dimmer-Interface PCB and Setup Instructions.
A prior post described the development and build of a clock to display time and date for UTC and Local. The clock characters are large,...
182 views0 comments
Dan Koellen AI6XG
- Apr 5, 2020
- 3 min
Auto Run for your Raspberry Pi - how to have your Rpi boot up in the desired configuration.
The Raspberry Pi (Rpi) is a great single board computer (SBC) that can be used in many projects and comes in different configurations. I...
74 views0 comments
Dan Koellen AI6XG
- Feb 9, 2020
- 9 min
Big Font Clock - Relieve for Old Eyes
Recently the Maker Space that I frequent received a number of 4 line 40 character (4 x 40) LCD displays. They asked me to figure out how...
657 views0 comments
bottom of page