

Dan Koellen AI6XG
- Jun 17
- 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.
20 views0 comments


Dan Koellen AI6XG
- May 16
- 6 min
Reactive Component Measurement With the NanoVNA
Exploration of using the nanoVNA to measure inductance and capacitance at frequency of use.
61 views0 comments


Dan Koellen AI6XG
- Mar 2
- 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...
265 views0 comments


Dan Koellen AI6XG
- Jul 30, 2021
- 2 min
Leg Benchmark W7Y/EW-017 Activation - An Alternative Route From the West
Pole Mountain From My Operating Position Summit Trip Summary Distance: ~ 2.6 mi one way Transport: Hiking Elevation Gain: ~500 feet...
36 views2 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...
519 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...
591 views0 comments


Dan Koellen AI6XG
- Apr 26, 2021
- 3 min
Schallenberger Ridge W6/NS-213 Activation - An Alternative Route
A different approach to Schallenberger Ridge from the west. A nice hike through historic train tunnels.
30 views0 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.
163 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...
78 views1 comment


Dan Koellen AI6XG
- Jan 25, 2021
- 1 min
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...
301 views0 comments


Dan Koellen AI6XG
- Dec 15, 2020
- 2 min
Mount Rose W7N/WC-001 Activation
Lake Tahoe and Tamarack Peak From Mount Rose Summit Trip Summary Distance: ~ 4.9 mi one way Transport: Hiking Elevation Gain: ~1800...
225 views0 comments


Dan Koellen AI6XG
- Dec 13, 2020
- 2 min
Tamarack Peak W7N/WC-003 Activation
Lake Tahoe From Tamarack Peak Summit Trip Summary Distance: ~ 1.3 mi one way Transport: Hiking Elevation Gain: ~960 feet Time: ~ 0.75...
86 views0 comments


Dan Koellen AI6XG
- Dec 10, 2020
- 3 min
Mount Houghton W7N/WC-002 Activation
Operating Position on Mount Houghton, Mount Rose W7N/WC-001 in Background Summit Trip Summary Distance: ~ 4.8 mi one way Transport: ...
46 views0 comments


Dan Koellen AI6XG
- Dec 3, 2020
- 2 min
Scott Peak W6/NS-153 Activation
Operating Position on Scott Peak Summit Trip Summary Distance: ~ 4.2 mi one way Transport: Hiking Elevation Gain: ~1700 feet Time: ~2...
57 views0 comments


Dan Koellen AI6XG
- Nov 29, 2020
- 5 min
Granite Chief W6/NS-115 Activation
Operating Position on Granite Chief Summit Trip Summary Distance: ~ 4.6 mi one way Transport: Hiking Elevation Gain: 2748 feet Time:...
34 views0 comments


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...
48 views0 comments


Dan Koellen AI6XG
- Oct 4, 2020
- 8 min
Trapped 20/30/40 Meter EFHW Antenna
An End Fed Half Wave (EFHW) antenna for operation on 20, 30 and 40 meters was built for SOTA operation. By using traps, the antenna...
5,381 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,...
144 views0 comments


Dan Koellen AI6XG
- Jun 6, 2020
- 4 min
End Fed Half Wave Antennas: More About the Primary Capacitor
I recently posted a blog claiming that a capacitor in the primary of the matching transformer is not needed for end fed half wave (EFHW)...
4,294 views1 comment


Dan Koellen AI6XG
- May 27, 2020
- 3 min
End Fed Half Wave Antennas: Is a Primary Capacitor Really Needed?
In my research on End Fed Half Wave (EFHW) antennas I found that nearly all have a capacitor in the primary (rig) side of the transformer....
10,801 views3 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...
54 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...
417 views0 comments


Dan Koellen AI6XG
- Jan 12, 2020
- 3 min
Castle Peak W6/SN-038 Activation
Operating Position on Castle Peak Looking Southwest Summit Trip Summary Distance: ~ 3.5 mi one way Transport: Hiking Elevation Gain: ...
102 views0 comments


Dan Koellen AI6XG
- Jan 12, 2020
- 4 min
Sand Ridge W6/NS-155 Activation
Operating Position Looking South From Sand Ridge Summit Trip Summary Distance: ~ 6.5 mi one way Transport: Hiking Elevation Gain: 1200...
42 views0 comments


Dan Koellen AI6XG
- Jan 11, 2020
- 2 min
Mount Lincoln W6/NS-149 Activation
Looking east from Mt. Lincoln, Tinker Knob W6/NS-121 is hiding behind Anderson Peak Summit Trip Summary Distance: ~ 3 mi one way...
51 views0 comments


Dan Koellen AI6XG
- Jan 11, 2020
- 2 min
Signal Hill (7751) W6/NS-393 Activation
Looking east from Signal Hill, Donner Lake is in the background and Lake Angela in the foreground Summit Trip Summary Distance: ~ 2 mi...
89 views0 comments


Dan Koellen AI6XG
- Jan 9, 2020
- 3 min
Tinker Knob W6/NS-121 Activation
Summit Trip Summary Distance: 7.2 mi one way Transport: Hiking Elevation Gain: 1870 feet Time: ~3.5 hours one way Route: Via Pacific...
56 views0 comments


Dan Koellen AI6XG
- Jan 6, 2020
- 6 min
How to do a SOTA Activation
SOTA activations are challenging and with risk, be sure you are experienced in hiking, navigation and survival skills.
120 views0 comments


Dan Koellen AI6XG
- Dec 23, 2019
- 3 min
SOTA - What is it? Why I do it
What is SOTA? SOTA, or Summits On The Air, is basically an activity where ham radio operators take their radio equipment to a hill or...
81 views0 comments