A 40 - 10 meter QMX
The QMX from QRP Labs is modified for operation from 40 to 10 meters. A perfect SOTA rig when matched to a 40 meter EFHW
Dan Koellen AI6XG
Jun 27, 20248 min read
2,007 views
1 comment
LCD Display for the KD1JV TriBander
In an earlier post I described the modifications I made to the KD1JV designed TriBander to make it more useful for SOTA. The...
Dan Koellen AI6XG
May 9, 20249 min read
300 views
1 comment
Making the KD1JV Tri-Bander More SOTA Friendly
This post outlines the modifications made to reduce receive current consumption, reduce weight and size, and change the controls and readout
Dan Koellen AI6XG
Jul 18, 202311 min read
838 views
0 comments
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...
Dan Koellen AI6XG
May 2, 20236 min read
457 views
0 comments
QRP Tube: T/R Switch and QCX Interface and Modification
A Modified QCX and TR Switch for Vacuum Tube SOTA transmitter
Dan Koellen AI6XG
May 2, 20236 min read
396 views
0 comments
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...
Dan Koellen AI6XG
May 2, 202316 min read
597 views
0 comments
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.
Dan Koellen AI6XG
May 2, 20235 min read
1,872 views
0 comments
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...
Dan Koellen AI6XG
Feb 28, 20235 min read
3,181 views
0 comments
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.
Dan Koellen AI6XG
Jun 17, 20226 min read
2,046 views
1 comment
Reactive Component Measurement With the NanoVNA
Exploration of using the nanoVNA to measure inductance and capacitance at frequency of use.
Dan Koellen AI6XG
May 16, 20226 min read
3,721 views
0 comments
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...
Dan Koellen AI6XG
Mar 2, 202211 min read
2,391 views
0 comments
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...
Dan Koellen AI6XG
Jul 30, 20212 min read
113 views
2 comments
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...
Dan Koellen AI6XG
Jul 20, 20219 min read
690 views
0 comments
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...
Dan Koellen AI6XG
Jun 16, 202113 min read
2,244 views
3 comments
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.
Dan Koellen AI6XG
Apr 26, 20213 min read
87 views
0 comments
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.
Dan Koellen AI6XG
Apr 25, 20219 min read
353 views
0 comments
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...
Dan Koellen AI6XG
Jan 25, 20212 min read
258 views
1 comment
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...
Dan Koellen AI6XG
Jan 25, 20211 min read
1,137 views
0 comments
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...
Dan Koellen AI6XG
Dec 15, 20202 min read
304 views
0 comments
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...
Dan Koellen AI6XG
Dec 13, 20202 min read
220 views
0 comments
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: ...
Dan Koellen AI6XG
Dec 10, 20203 min read
129 views
0 comments
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...
Dan Koellen AI6XG
Dec 3, 20202 min read
134 views
0 comments
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:...
Dan Koellen AI6XG
Nov 29, 20205 min read
82 views
0 comments
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...
Dan Koellen AI6XG
Nov 23, 20201 min read
93 views
0 comments
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...
Dan Koellen AI6XG
Oct 4, 20208 min read
10,831 views
0 comments
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,...
Dan Koellen AI6XG
Jun 29, 20207 min read
219 views
0 comments
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)...
Dan Koellen AI6XG
Jun 6, 20204 min read
9,409 views
3 comments
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....
Dan Koellen AI6XG
May 27, 20203 min read
23,652 views
4 comments
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...
Dan Koellen AI6XG
Apr 5, 20203 min read
100 views
0 comments
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...
Dan Koellen AI6XG
Feb 9, 20209 min read
949 views
0 comments
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: ...
Dan Koellen AI6XG
Jan 12, 20203 min read
158 views
0 comments
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...
Dan Koellen AI6XG
Jan 12, 20204 min read
110 views
0 comments
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...
Dan Koellen AI6XG
Jan 11, 20202 min read
113 views
0 comments
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...
Dan Koellen AI6XG
Jan 11, 20202 min read
216 views
0 comments
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...
Dan Koellen AI6XG
Jan 9, 20203 min read
98 views
0 comments
How to do a SOTA Activation
SOTA activations are challenging and with risk, be sure you are experienced in hiking, navigation and survival skills.
Dan Koellen AI6XG
Jan 6, 20206 min read
665 views
0 comments
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...
Dan Koellen AI6XG
Dec 23, 20193 min read
317 views
0 comments
