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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
2,038 views
1 comment


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
3,192 views
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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
2,054 views
1 comment


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
2,402 views
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