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
May 99 min read
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...
250 views0 comments
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
753 views0 comments
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...
458 views0 comments
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.
1,506 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...
2,337 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.
1,519 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.
3,098 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...
2,129 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...
667 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...
1,926 views3 comments
Dan Koellen AI6XG
Oct 4, 20208 min read
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...
10,087 views0 comments
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
Jun 6, 20204 min read
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)...
8,896 views1 comment
Dan Koellen AI6XG
May 27, 20203 min read
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....
21,739 views4 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...
866 views0 comments
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