MEF-107-4K Multi-Band End Fed Half Wave Antenna Transformer 75:1 Ratio (3750:50 Ohms)
Now you can make your dream low band antenna with just 259 feet of wire (~79m) and operate on low bands without the use of a tuner at legal power using as much as 4kW ICAS.
Features massive ferrite core weighing 1.65 pounds (0.75kg) and very low Insertion loss <0.16dB
This is an End-Fed Half-Wave antenna (EFHW) transformer covering 160/80/60/40m amateur bands or any frequency in between. It transforms high impedance ~3500 Ohms at the end of the half-wave radiator to 50 Ohms and features very low insertion loss. Average insertion loss from 1.8-7.3MHz is less than 0.16dB
- NO TUNER needed!
- NO counterpoise needed! (Grounding recommended)
- Just adding a wire radiator of ~259 feet makes this antenna resonant on 160/80/60/40m.
- The wire of ~133 feet will give you low VSWR on 80 and 40m.
- Frequency coverage: 1-7MHz
- Power Handling: 4kW I.C.A.S
- Polycarbonate housing
- Hardware: Stainless Steel
- Connector: Silver/Teflon SO-239
Just add 1/2 half-wave wire to this transformer and tune the length to your preference. Note that the antenna will be working on multiple frequencies. Half-wave for 160m (~256 feet) will be two half-waves on 80m and four (4) half-wave on the 40m bands. If you desire to use it on a 30m or new 60m band only, just cut the half-wavelength wire for that frequency or any frequency from 1-10MHz. The wire length can be calculated by the following formulas:
- Length (feet)= 468/Frequency (MHz) or
- Length (meters)=142.5/Frequency (MHz)
Always cut a wire a bit longer to allow for tuning to your desired frequency. Tuning depends on height above ground and nearby objects. There are so many ways to install the wire and your imagination is only limit. You can do it horizontal, vertical, sloping, an inverted “L” shape, Horizontal “L”, in “inverted “V” shape, etc.
NOTE: the minimum recommended height for a horizontal portion of the antenna is 0.1 wavelengths above ground (~50 feet or 15 meters for 160M band). Yes, it can work also at 30 feet above the ground but with less efficiency due to increased ground loss (absorption).
Such an antenna will not need radials and in most cases NO Tuner at all. Be a HAM and do some experiments.
Grounding at the lug next to the SO239 connector is recommended! Long wires tend to collect electrostatic charges (usually when the weather is stormy) which can produce ESD (electrostatic discharge) at the end of your cable and damage your equipment.