Tuning the 40m Coil

With the current settings on 30m (26cm 2.5 turns shorted), fc on 40 shifted to 7.188 MHz – even with 8 turns shorted. Moving the shorting strap to 7 turns, fc shifts to 6.988 MHz. With 7.5 turns shorted fc = 7.039 MHz.

 L40=26cm 8t fc=7.166M

L40=26cm 7t fc=6.988M L40=26cm 7t5  fc=6.988M
HF2V SWR on 40  HF2V SWR on 40  HF2V SWR on 40

Unfortunately, this influenced the 30 meter band as well shifting the resonance down, but still SWR below 1.5 within 10.100-10.150 MHz. No influence on 15.

FYI, an index of all SWR graphs can be found here.

Author: Alexandru Csete

Embedded software engineer in the satcom industry during the day. Radio amateur and SDR hacker during the night.