Performance

First impressions of the antenna were favorable. Overall, the 5BTV outperformed my former windom antenna on all bands. However, the windom was never installed at optimum height and was very close to trees.

The most useful performance test was last field day, when I put up a homebrew 20M monoband vertical with 8 radials (antenna base 45' high) and a homebrew 40-10 trap dipole mounted as a sloper with the highest point at 35'.

Consistently, the 5BTV was outperformed by the monobander and dipole. On 20 and 40, the 5BTV exhibited 2 or 3 s-units weaker reception than the higher antennas. Weak stations were often heard by the monobander or dipole, but not with the 5BTV.

Here are the SWR curves after installation with 40 radials:







The very narrow bandwidth on 80 was expected, and indicates that the antenna is working. However, the relatively high SWR on 40 was a surprise, although my antenna tuner could handle it. I contacted technical support and was advised to install a coil between the radiating element and ground as shown:


This lowered the SWR at 7.2Mhz to 1.5:1, with the curve following along. 80M reception was slightly degraded after the installation of the coil, and AM broadcast reception was significantly degraded. As I enjoy using my HF rig to listen to AM broadcast, I decided to reject the coil "fix" and let the antenna tuner deal with 40M.

The SWR curves after increasing to 60 radials and then to 124 radials did not vary significantly. The slight variances may be caused by seasonal changes and moisture content of the soil.