Antenna, Short Dual Dipole, Portable, NVIS, 80 and 40 Meters Dual Band, Kit
|Wire Antenna Band|
DX Engineering 8040 NVIS Antennas: Near Vertical Incidence Skywave (NVIS) is a propagation mode which uses high-angle radiation that sends signals almost straight up! They are then reflected back to Earth for very effective short to medium distance communications that works virtually every day and every evening.
NVIS dipoles are almost omnidirectional and height is not a requirement.
These 80 and 40 meter wire antennas work very well with their feedpoint at only 15 feet above the ground, supported by the included mast. The support ropes tied to the wire dipole end- insulators are used as guys for the support mast, and are secured to the ground with tent stakes!
DXE-NVIS-8040S and the DXE-NVIS-8040 antenna kits are complete with everything required; the fiberglass mast (four, 4 ft. sections that extend to 15 ft.), a COMTEK COM-BAL-11150T balun, a balun mounting kit, coax strain relief bracket, antenna wire, insulators, four stakes, rope, and a 100 ft. RG-8X coax assembly with PL-259s! The four legs of the antenna, each deployed 90 degrees apart, provide the mast guying.
The DXE-NVIS-8040S is a shortened NVIS wire antenna kit version that features loading coils to make the 80 meter dipole legs the same length as the 40 meter dipole legs, 34 ft., so this antenna fits into a square area that is only about 50 ft. by 50 ft.
The DXE-NVIS-8040 is full size, with 67 ft. wire dipole antenna legs for 80 meters and 34 ft. legs for 40 meters and it fits into a rectangular area approximately 100 ft. by 50 ft.
NVIS rarely works at frequencies outside the range of 2 MHz to 10 MHz. The signal must penetrate the D layer of the ionosphere and bounce off the F layer. Signals on frequencies below 2 MHz will not penetrate the D layer; frequencies higher than 10 MHz will not bounce off the F layer at these sharp angles, they penetrate and continue out into space.
Regular-height dipoles or vertical antennas have a lower take off angle and your signal may be heard three states away, but not in your own state due to the “skip zone.” This skip zone is the area between the maximum ground wave distance and the shortest sky wave distance where no communications are possible. Depending on operating frequencies, antennas, their height above ground and propagation conditions, this skip zone can start at roughly 10 to 20 miles away and extend out to several hundred miles.
NVIS mode of operation makes it ideal for in-state and next state communications during disasters or other emergency situations. The military has used NVIS techniques for decades to provide short haul communication with other units on the ground. This is why these antennas are ideal for round-table gatherings with regional ham friends on 40 and 80 meters, day to day and night after night.
These antennas are easy to deploy and are great for camping, RVs, QRP, ARES, EMCOMM, SPOTA and any other use where short range HF operation on 80 or 40 meters is desirable. They are actually pretty stealthy, too! Due to their near vertical radiation, NVIS dipoles are almost omnidirectional. They even have a legal-limit power rating!
Remember, Amateur Radio operators look to 80 and 40 meters for short skip NVIS operations. Order DX Engineering 8040 NVIS Antennas and fill in the skip zone!