Description
MEF-307-4K Multi-Band End Fed Half Wave Antenna Transformer 70:1 Ratio (3500:50 Ohms)
Now you can make your dream low-band antenna with just 133 feet of wire (~40.5m) and operate on 80 and 40M bands without the use of a tuner at legal power using as much as 4kW ICAS and full legal power 1500W on FT8/ Digital modes
Features massive ferrite core of three (3)stacked 3.1 inches (79mm) in diameter and very low Insertion loss of less than 0.2dB
This is an End-Fed Half-Wave antenna (EFHW) transformer covering 80/40m 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 3-8MHz is less than 0.2dB
- NO TUNER needed!
- NO counterpoise is needed! (Grounding recommended)
- Just adding a wire radiator of ~133 feet makes this antenna resonant on 80/40m.
- The wire of ~67 feet will give you a low VSWR on 40m or ~123 feet on a 75m band
- Frequency coverage: 3-8MHz
- Power Handling: 4kW I.C.A.S
- FT8/Digital modes at 1500W continuous!
- Polycarbonate housing
- Hardware: Stainless Steel
- Connector: Silver/Teflon SO-239
Assembly
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-waves for 80m (~133 feet) will be two half-waves for 40m If you desire to use it on any frequency between 3-7MHz, just cut the half-wavelength wire for that frequency. 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 the height above ground and nearby objects. There are so many ways to install the wire and your imagination is only limited. You can do it horizontally, vertically, sloping, in an inverted “L” shape, Horizontally “L”, in “an 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 the 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.
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