Bottom section of antenna
I designed this antenna to withstand the harsh
wind, salt, and lightning conditions of the south. It's made of 6063-T6
aluminum and uses all stainless steel hardware. The bottom coil is made
of 5/16" solid rod. The top of the antenna is terminated with a solid
aluminum static dissipating tip. The RF is fed to the tuning coil through
a heavy duty silver plated strap and Amphenol connector. The strap connects
to the coil with a moveable clamp that is adjusted along with antenna
length for best match.
I built this antenna as a high efficiency replacement to the common fiberglass antennas. Aluminum antennas do not attract lightning like the fiberglass types, due to there ability to dissipate static out of the air. This antenna is tunable from 25 to 30 MHz. It is designed to be mounted on top of a supporting mast or tower. The mounting sleeve fits over 1-1/4 inch mast and secures with two 1/4x20 stainless bolts. This antenna can survive winds in excess of 80 mph.
questions, comments, antenna orders,
SPECS: Wolf Point 50_11m
The gain of a omni-directional antenna comes from bringing energy that's being wasted into the sky down to the ground. Two basic factors control this effect, the length of the antenna and it's height above the ground. The diagram below shows the side view of the lobe pattern coming from a 1/4 wave, (black line) 1/2 wave, (blue line) and .64 wave (red line) antenna at a height of one wavelength. The antenna is located at the bottom left corner of graph. The vertical axis points strait up and the horizontal axis is level to the ground. The difference is obvious, the pattern of the 1/4 wave is almost round and the pattern of the .64 is much flatter the difference in gain is almost 4 dB. This is called the "angle of radiation" or just "radiation angle" and is stated in degrees above the horizon.
(NOTE: Secondary lobe of .64 ommited
So then the gain is achieved by moving energy that went almost strait up and getting it down onto the ground where the receiving antennas are. The radiation angles are as follows: 1/4 wave = 32 deg., 1/2 wave = 24 deg., .64 wave = less than 15 deg. It can now be seen that the lower the angle of radiation the greater the distance will be. This is true for local and DX.