A Space Saving 80 meter antenna
Constructing an Electrically Shortened 80-Meter End-Fed Wire Antenna with Loading Coils
Description
The NB6Zep Antenna, an electrically shortened 80-meter end-fed wire, addresses space constraints for low-band operation by integrating two loading coils into a 37-foot wire. This design, modeled with EZNEC, explores configurations like the quarter-wave sloper and inverted-L, with the latter providing a more vertical radiation pattern and practical backyard deployment. The resource details specific coil construction, recommending 21 uH coils made from BW coil stock #3026 or similar, and outlines wire segment lengths for optimal tuning.
Performance analysis indicates a radiating efficiency of approximately 27% with good ground conductivity, resulting in a signal typically 3-4 dB down compared to a full-size quarter-wave vertical. The antenna exhibits a narrow bandwidth, around 50 kHz, due to its high Q, necessitating a tuner for broader band operation. Feedpoint impedance is low, with ground resistance playing a critical role in achieving a usable SWR.
The article emphasizes the importance of an effective ground rod at the feedpoint for proper operation and tuning, suggesting an antenna analyzer for precise adjustments. It confirms the antenna's suitability for DX, citing successful contacts from Oregon to the East Coast and Hawaii on a 160-meter variant, making it a viable option for urban operators seeking low-angle radiation on 80 meters.