Antennas for SOTA

Dan Koellen AI6XG

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

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

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

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...

6,721 views0 comments

Dan Koellen AI6XG

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)...

5,860 views1 comment

Dan Koellen AI6XG

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....

13,709 views3 comments