5 out of 5 based on 4 customer ratings
(4 customer reviews)

Product Description

MEF-310-2K Multiband EFHW Antenna Transformer,  Covers 3 Bands / 80-30m / 1kW-max. /  NO TUNER needed / wire not included/ one End Insulator included


MEF-310-2K Multi-Band End Fed Half Wave Antenna Transformer

This is an End-Fed Half-Wave antenna (EFHW) transformer covering 80/40/30m amateur bands or any frequency in between. 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 wave length wire for that frequency or any frequency from 1-10MHz. Wire length can be calculated by following formulas:

  • Length (feet)= 468/Frequency (MHz) orlongwire1
  • 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 is 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, Zigzag, etc.

Such 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 single transformer is half of the measured values showed  the plot.

Total loss: 3.65MHz is 0.14dB, 5.4MHz is 0.09dB, 7.1MHz 0.14dB and 10.1Mhz 0.31dB


MEF-310-2K  transformer insertion loss




SKU: MEF-310-2K Categories: ,

4 reviews for MEF-310-2K

  1. 5 out of 5


    I have installed 40m radiator configuration at about 6m hight.Since I had lot of spare copper wire from previous prijects, layed it down as radials with grounding (5 X 10m). I have managed to tune it on 80 and 40m band. Target was 3.520Mhz and got SWR 1:1.15( 1:1.15 on 3.505) and preaty flat (5mm2 copper wire) and still needs some triming. On 40m band it was centered on 7.110MHz (bit of center for me) but it is very good 1.1 and flat troughout 50kHz. Results on 80m are so far beyond expectations, 1st QSO on my CQ wad ZL2IFB at 21.10 my local (as far me, that is great!!!) Worked CQ Mir (16.05.2015) contest 80m band CW, finished with 190 QSOs (until 01.00GMT, could not stay longer), have worked evry station I have heard. Left WSJT-X on 80m trough night to check out what is going on during night, and found lot of activity from NA until 03.00 GMT (will stay wake one night (: )
    40m band, o one side I a working almoast evry thing that I tried so far on few contests I have been. WSJT-x rx great (worked WAC in first few days- 20-30W)!!! only not satisfied with readings on reverse beacon, in some way it looks strange (too low or to high on unexpected sides).
    80m radiator follows, found some space for it and will follow up.


  2. 5 out of 5


    I had a dilemma: My wife wanted no more wires in the back yard. I already have a MA-55 telescoping 55 ft tower, and wanted to have an antenna for 75 meter rag-chewing at up to 500 miles. I decided to arrange a shortened dipole between my chimmneys, fed with open wire. Did not work well at all, and wife hated the ugly open wire in the middle of the roof! Danny suggested using the MEF-110-1K and feed the antenna as end fed at about 124 ft long, even though about 50 ft stretches to a tree on the end of the lot line. Wire is #18 and almost invisible, and feed point is at one end and not very visible on the roof. Antenna works GREAT even though 65 ft of it is only 3 ft off the peak of the roof. THANK YOU DANNY!

  3. 5 out of 5


    Update on MEF-110-1K , 80m of 4mm wire at 7m high. Instaled huge contapouse system, works great!!!

  4. 5 out of 5


    Most of my QSOing is of the rag chew variety and at times they can get quite lengthy. I usually operate on 40 and 80 meters running about 1kw, or more, especially during these times of poor propagation. I was looking for a transformer that could handle high power for extended periods of time and not burn out or overheat, so I installed the MEF-310-2K. The unit handled everything I threw at it and the SWR remained consistent throughout. I’ve been very pleased with its performance. I would highly recommend the MEF-310-2K if you operate your station at high power levels as I do. Danny is great to work with. He was very helpful in assisting me with some of the issues I was having. Thanks!

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