Dan Koellen AI6XG
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
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Dan Koellen AI6XG
Jul 18, 202311 min read
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
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Dan Koellen AI6XG
May 2, 20236 min read
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...
361 views0 comments
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
289 views0 comments
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.
1,518 views0 comments
Dan Koellen AI6XG
Feb 28, 20235 min read
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...
2,367 views0 comments
Dan Koellen AI6XG
Jun 17, 20226 min read
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.
1,526 views0 comments
Dan Koellen AI6XG
May 16, 20226 min read
Reactive Component Measurement With the NanoVNA
Exploration of using the nanoVNA to measure inductance and capacitance at frequency of use.
3,113 views0 comments
Dan Koellen AI6XG
Mar 2, 202211 min read
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...
2,138 views0 comments
Dan Koellen AI6XG
Jul 20, 20219 min read
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...
668 views0 comments
Dan Koellen AI6XG
Jun 16, 202113 min read
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...
1,941 views3 comments
Dan Koellen AI6XG
Apr 25, 20219 min read
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.
338 views0 comments
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...
223 views1 comment
Dan Koellen AI6XG
Nov 23, 20201 min read
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...
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Dan Koellen AI6XG
Jun 29, 20207 min read
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,...
217 views0 comments
Dan Koellen AI6XG
Apr 5, 20203 min read
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...
95 views0 comments
Dan Koellen AI6XG
Feb 9, 20209 min read
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...
875 views0 comments
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