Description
MEF-130-2K-Plus Multi-Band End Fed Half Wave Antenna Transformer 49:1 Ratio
Features massive ferrite core weighing 1.25 pounds (0.54kg) and very low Insertion loss ~0.5dB
This is an End-Fed Half-Wave antenna (EFHW) transformer covering 160/10m amateur bands or any frequency in between. It transforms high impedance ~2500 Ohms at the end of the half-wave radiator to 50 Ohms and features very low insertion loss. Average insertion loss from 1.8-30 MHz is ~ 0.5 dB
NOTE: for decent efficiency and match the minimum height for a horizontal portion of the antenna is 0.1 wavelength above ground. Also, the wire cut for 1.8-2MHz will not produce harmonics in all the amateur bands up to 30MHz. They are not harmonically related ie 1.8-2MHz times 2,3,4,5,6…
- NO TUNER needed!
- NO counterpoise needed! (Grounding recommended)
- Frequency coverage of the transformer only: 1-30 MHz
- Power Handling: 2kW I.C.A.S
- Polycarbonate housing
- Hardware: Stainless Steel
- Connector: Silver/PTFE (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-wave for 160m (~259 feet) will be two half-waves on 80m and four (4) half-wave on the 40m band etc. 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 the only limit. You can do it horizontal, vertical, sloping, an inverted “L” shape, Horizontal “L”, in “inverted “V” shape, etc.
Such an antenna will not need radials and in most cases NO Tuner at all. Be a radio amateur 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.
joe mancos –
This antenna performs above and beyond what is advertised and expected.
Paul B. –
Great Box!! I’ve worked the world off it on 100watts (132ft 12ga wire)and a powerhouse when my SB220 is in action! I definitely recommend this product.
MICHAEL O’CULL –
george –
mark n. –
Mark –
top quality and great performance
William Hagen –
Excellent.
Roman Tomas –
working well, quality is perfect
Tom Lewis –
I have had the MEF-130-2k-PLUS up for several weeks now and I’m very pleased. Matching across the bands from 80 through 10m is very good. The transformer purports to provide 160m, but I do not use, and have not tested it in this capacity.
My main use of the MEF-130-2k-PLUS is SSB phone up to about 1.2kW, and there have been NO core heating issues whatsoever. One must of course be aware of any impedance mismatch across the transformer and not drive non-resonant portions of the bands with an excess of power – ie., in the 80/75, band. Though it does take a little time, make the effort to provide a compensation coil to lower the resonance of the higher frequencies, and provide a proper capacitor/bleeder resistor mid-point of the wire to raise the resonance of the 80m band if needed. MyAntennas does sell wires constructed in this manner if needed.
For CW I will very rarely use more than 100W though I suspect this transformer will remain cool up to several hundred watts of CW use. For digital modes I don’t use more than 50W – typically 15-25W. If you require more power for CW consider using the MEF-330-2k-PLUS. I do not recommend using excessive power in digital modes, particularly weak signal modes.
The antenna I use with the MEF-130-2k-PLUS is far from an ideal “text book” example due to trees, buildings, etc. It is #13 stranded/insulated wire deployed as an inverted L with the feed point at 6 ft. and the horizontal portion @ 50-60ft. The transformer is tied to an 8′ ground rod directly below the transformer, and a 0.05L counterpoise is attached. Matching from 40m – 12m is <1.1:1 at the each resonant point within each band, and <2:1 through the entire 40m band. From 28-29MHz matching is <2:1 with the resonant point @1.4:1. In the 75/80m band the resonant point is @ 1.5:1, but given the 500kHz window of 80/75, one must "target" where they want the wire to be most resonant, and exercise caution with power levels as outside of the resonant region the mismatch across the transformer will be higher.
The construction of the housing for the transformer is top-notch. A vent is provided for temperature equalization on the side, and a weep hole/vent at the bottom to allow condensation to drain. Mounting holes are provided in the four corners, as well as a top and bottom center opening that will accommodate a "slide and lock" type of screw-mounting for easier installation and removal. My only complaint in construction is the 10-24 hardware for the antenna wire and ground/counterpoise connections. I drop a LOT of wingnuts, and 10-24 are just easier to lose. 1/4-20 would be a welcome improvement. This, however, is a small issue, and a trip to the hardware store for a handful of 10-24 wingnuts solved the "problem" for me.
Conclusion: This is an excellent, well built transformer, and if you don't want to get into the time consumption of building your own (and it DOES take time), then this is the best example I've seen. You will have to spend time getting your wire trimmed and deployed, and will likely need a compensation coil and/or mid-point capacitor to place band resonances where you need them depending on your operating style and modes. As far as not needing a matching unit (tuner): if you are using power such as this transformer provides then you already own a tuner, and if you don't, you need to have one in your arsenal of radio tools.
Mark McClellan –
So far, the antenna is doing great, and I have run nearly legal limit through it on 160M many times. One of the 1st nets I joined, and band conditions were pretty good I worked nearly to entire list. Even had someone ask what antenna I was running after the net. The reason I bought the antenna was for 160M and after March I may put a wire length for 80M to have an additional antenna for it.
Only issue is how long it took to get from FL to MS. It stopped like 5 different places before being delivered. Don’t know if it was the way they shipped it or just how bad the mail service has become lately.
I would buy again from the company after looking and the quality of the product.
Robert Thompson –
Excellent product. Only issue is that I did not receive my complete order. I paid for2 of the MEF-130-2K and only received one.
Danny-E73M –
We are sorry about that but you did not use contact page to tell us about missing product. You did not have to wait for 30 days and tell us in the review. We are shipping second unit today.