MEF-310-2K Multi-Band End Fed Half Wave Antenna Transformer
This is an End-Fed Half-Wave antenna (EFHW) transformer covering 80/60/40/30m amateur bands or any frequency in between (3-10MHz). It transforms high impedance ~3000 Ohms at the end of half wave radiator to 50 Ohms and features very low insertion loss.
- NO TUNER needed!
- NO counterpoise needed! (Grounding recommended)
- Just adding a wire radiator of ~132 feet makes this antenna resonant on 80/40m.
- The wire of ~132 feet (40.23meters) will give you low VSWR on 80/40m.
- Frequency coverage: 3-10MHz
- Power Handling: 2kW I.C.A.S
- Weight: 1.25 lbs. (0.7kg)
- 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 antenna will be working on multiple frequencies. Half wave for 80m (~132 feet) will be half wave on 80m and two (2) half wave on 40m band. If you desire to use it on 30m or new 60m band only, just cut the half wavelength wire for that frequency or any frequency from 1-10MHz. 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, in inverted “L” shape, in “inverted “V” shape, etc.
Such an antenna will not need radials and in most cases NO Tuner at all. You can use it as vertical against good radial counterpoise too. Be a HAM and do some experiment.
Grounding at the lug next to the SO239 connector is recommended! Long wires tend to collect electrostatic charge (usually when the weather is stormy) which can produce ESD (electrostatic discharge) at the end of your cable and damage your equipment.
Insertion Loss measurements of MEF-310-2K transformer
NOTE: this plot shows an S21 measurement of two (2) transformers connected back to back and total insertion loss of a single transformer is half of the measured values showed the plot.
Total loss: 3.8MHz is 0.05 dB, 5.4MHz is 0.06 dB, 7.1MHz 0.11 dB