Engineering the EFHW 49:1 Transformer and Antenna

After doing the ferrite transformer scaling experiments last time, and learning a bit more about what matters in these transformers, it was time to make a stab at designing one. Let me review the salient observations from the previous work. 1) More primary turns and primary inductance improve the transformer efficiency and low end performance. [...]

Designing Self Resonant Coils for Antenna Traps and Chokes

A lowly coil of wire can be surprisingly difficult to understand and model correctly.  I use coils of wire or coils of coax cable as trap inductors for various antenna designs that I have built.  In the low frequency limit, the traditional inductance calculations work okay and can give you a pretty good estimate of [...]