Description
MEF-330-1K-Plus Multi-Band End Fed Half Wave Antenna Transformer 56:1 Ratio
Features three 2.4-inch ferrite cores and very low average Insertion loss ~0.37dB
The MEF-330-1K-Plus is a high-performance end-fed half-wave (EFHW) transformer for hams who want to cut their own wire and build a custom antenna. Covering 80m-10m (3.5-30MHz), it transforms the high impedance (~2,800 Ohms) at the end of a half-wave radiator down to 50 Ohms — no tuner required on the harmonic bands.
Important: This is a transformer only. Wire is sold separately. See our wire assemblies or cut your own using the formulas below.
Built with three 2.4-inch ferrite cores, the MEF-330-1K-Plus delivers exceptionally low insertion loss — averaging just 0.37 dB from 3.5-30MHz. See the measurement chart in the image gallery for actual test data.
What’s Included:
- MEF-330-1K-Plus transformer
- One end insulator
- Two wire clamps
- Optional pole mounting plate (select at checkout)
Features:
- Frequency coverage: 3.5-30MHz (80m-10m)
- Transformation ratio: 56:1 (2,800:50 Ohms)
- Power handling: 1kW ICAS (SSB/CW), 250W continuous (FT8/digital)
- Average insertion loss: ~0.37 dB
- Silver/PTFE (Teflon) SO-239 connector
- All stainless steel hardware
- Durable polycarbonate enclosure
No tuner needed on harmonic bands. No counterpoise needed — the antenna finds its ground path through the coax shield grounded at your home entrance.
Wire Length Formulas:
- Length (feet) = 468 ÷ Frequency (MHz)
- Length (meters) = 142.5 ÷ Frequency (MHz)
Example: For 80m CW (3.55 MHz): 468 ÷ 3.55 = 132 feet
Always cut the wire a few feet longer than calculated to allow for tuning. A half-wave wire for 80m will give you eight harmonic resonances up to 10m.
Installation Options:
The wire can be installed horizontally, vertically, sloping, inverted-L, inverted-V, or even zig-zagged through trees. Your imagination is the only limit. Keep the wire as high as practical — minimum 20 feet at any point for 80m operation.
Grounding Recommended: Connect a ground wire to the lug next to the SO-239 connector. Long wires collect electrostatic charges, especially in stormy weather, which can produce damaging ESD on your equipment. This also satisfies NEC-810 grounding requirements.
For the complete installation guide, see the EFHW Installation Manual.
Looking for a ready-to-use antenna? Check out our complete EFHW-8010 or EFHW-7510 antennas with pre-cut wire.
Dom, F4BWJ –
I’ve installed the MEF-330-1K with around 132ft of stainless 3mm diameter wire.
The MEF-330-1K is installed at 1,10m from the ground the wire goes quite vertically to 5/6m high and the rest of the wire goes to 12/13m high on the top of a tree.
First of all what is noticeable is the noise floor level which is lower than I got with other antennas such as G5RV, long Wire, dipole, Conrad Windom etc…
With the EFHW antenna the noise level is around 53 to 55 on 80m during the day as I get 57 to 59 with other antennas.
Also the received signals can be very strong in despite of low noise floor level (higher than a long wire or G5RV for example).
From South West part of France, my first contacts with this antenna on 80m have been made with only 100W from my SDR MB-1 early in the morning with north American stations between 6:00am and 7:00am UTC (NY2PO -5843kms, KK6ZM/1 -5386kms, W1/DL4NAC – 5562kms…), New Zeeland station (ZL1AIX – 19187kms) and just this morning 11/03/2016 at 6:45 UTC Cayman Island (ZF2ZB in a tremendous pile up with big guns stations all over Europe!!! – 7771kms)..
I’ve made some tests on 17m and 12m WARC Bands with success too (e.g. first contact on 12m band with CX7SS).
The sole problem I encounter is with 30m band, SWR is around 2,7/3.0 and in despite the ATU transceiver is normally able to tune antennas with such SWR, it’ cannot match my EFHW antenna. This is not very important for me as I don’t use this band.
In conclusion, very interesting beginnings for this homemade EFHW 132 ft. antenna fed with the MEF-330-1K transformer!!!
NB: I apologize for my broken english in this review as I’m a French ham.
Dom, F4BWJ.
Marcius E. Chester –
Danny all I can say is “WOW” this
MEF-330-1K Transformer attached to a 66′ 18g wire in a sloper/slanted L configuration up 35′ in a 40′ tree is the best antenna I have ever had. Due to living in a HOA development I’m not able to put a antenna on the roof. This transformer works perfect on 11 meters. Swr: 1.0: 26.965- 1.0: 27.405. Keep up the good work and think about building 64:1 transformers.
73
Rev. Doctor MC. Big Mac-233
Southern California
Carroll Peabody –
The My Antennas Transformer unit I purchased and used with my 130 foot end fed wire works very well. Compared with my existing 80/40 fan dipole it is about equal on the 80 and 40 meter bands. The only difference I notice is a little more noise is heard on the EF wire compared to the dipole. Probably due to antenna orientation at my location. I would recommend this antenna system as an easy way to get on the HF bands.
Paul –
Excellent product—my second purchase from myantennas. I had been using 2 ununs from another manufacturer, one rated for 100W ICAS and the other rated for 250W ICAS, but neither one could handle even 35W digital without the cores going into saturation! Since I had several years of experience using the high quality myantennas 80-10 EFHW antenna, this purchase was a “no-brainer”. I’m using this unun in the field in rugged mountainous terrain. It’s solidly built and performs exceptionally well. I highly recommend this product.
73 de K9PM
David K. –
Corey Becker –
I live in a condo on the second floor with attic access. My main antenna is an EFHW 56:1 balun (My Antennas MEF-330-1K-Plus) with 16’ 5” of 1/4 inch copper tubing configured as a 45 slope bottom fed with 75’ of LMR400. It tunes up 1.0 SWR @ 24.800Mhz to 1.8 SWR @ 29.700Mhz. I have worked 17 countries and 100’s of US contacts with 250W
Philip –
Works great on 20/40m fence antenna
Paul –
Mike V. –
I use this with 600 watt amp on SSB and have made contacts all around the world. I always get comments on how great my audio and signal is.
Tim B. –
Best quality EFHW transformer available. Used for 2 years now and I’m continually impressed.
Albert K. –
Great value for the money. Excellent hardware
TOM COUGHLIN –