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write your own review of the Myantennas EFHW-8010-2K .
Dec 29, 2016 12:07
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Wave of the Future
Time owned: 0 to 3 months
My matching box is at 55' with the far end at 35 feet. I am feeding it with LMR-600 (big stuff).
Performance is as good or better than my doublet fed with ladder line an tuner. I like this antenna because the swr is either low enough to not need the tuner or just a bit of tuning is needed to make the rig happy. The highest swr is on 30 meters, 2.5 - 1, easily tuned by the rig's internal tuner. Although the swr is high on 60 meters and 160 meters my autotuner - MFJ-998 easily matches the thing and I get plenty of QSOs. Yes I know it's not supposed to work there but it does and doesn't get hot.
With my old doublet, tuning was tricky and the auto tuner often complained especially if I tried to use a balun. Now with this new design it's a breeze to tune.
My only concern is the power rating. The 2kw ICAS really doesn't tell you much. I would never try running RTTY or any higher duty cycle mode with 2KW. With SSB you have no worries. The voltage at the end of this antenna would probably scare Tesla! In spite of the fact that CW is an off/on mode it still has a much higher duty cycle than SSB. I run 500 watts CW here. If I get involved in a long winded, high speed CW qso, the transformer will warm up but only on 80 meters.
I added about 6 feet of wire to the end and brought the swr down on 80. In fact, it seems that the higher you install this antenna, the longer it needs to be. Doing this has lowered the swr on all bands and solved the 80 meter heat problem. I still think there is room for improvement on the lowest band. If you didn't care to go higher than 30 meters you could consider his MEF-110HP-2K. I have not tried that product but it might handle power better on 80.
What's inside the magic box? Well I opened it up and found a stack of three 240 cores wound as an auto transformer. This design seems more popular in Europe an is catching on here. The impedance ratio is around 50:1. The cores have no coating or tape for protection and they are fastened down with a couple of wire ties. My wire ties were melted from all the 80 meter abuse. I replaced them. The inside of the box was very wet. There are two tiny weep holes in the bottom but these aren't doing the job. Warm transformers and cold air result in condensation. Some corrosion had already begun on the coax connector and solder. Somehow more ventilation is needed. I bored two large holes in the bottom and put some fiber mesh over them but really it needs more than this. I doubt if the power loss exceeds 10% on 80m with a higher SWR but with 500 watts that's 50 watts and the temperature can get pretty high inside. Don't be too concerned about a bit of loss. With my doublet running high power, the tuner and a balun would also get warm on the lower bands due to common mode current and antenna unbalance.
I have no signs of RFI anywhere. I'm using about 150 feet of LMR-600. The only ground is at the shack entry point. Keep in mind that line-chokes only work where there is current on the outer shield of the coax and the location of the current varies with the frequency. A choke mite work on one band at some point along the way but not on others. So far I haven't heard of any major concerns with RFI. I do intend to improve the grounding out closer to the antenna but mainly for lightning protection.
As for performance.... It's just wire and all the old rules apply. The higher the better as they say. Mounting the box low to the ground and running the wire high in a tree results in a high angle pattern. It's probably the worst way to install it but also the most common. Putting the box high in the tree and sloping the wire yields a low angle in the sloped direction. Putting it high and level is preferred if possible.
If you have been messing with end fed antennas you may have noticed the popular 9:1 unun method of feeding some odd length of wire. In fact, I have one up now at 117 feet long. It's way down in performance compared to the EFHW. It makes me wonder where all the power is going with those 9:1 jobs! I do not recommend the 9:1 design.
Price...Well $170 seems like a lot of money but compared to some if the multiband verticals it's dirt cheap. Look at a Butternut... $600 for a bit of aluminum and you still have to have radials then fiddle with tuning.
You won't find much in the theory books about this design. Most of what you can find on the web is QRP and uses extra coils with limitations on frequency. Myantennas has come up with a way to pack it all in one box. Hopefully Danny will continue to experiment and come out with even better products. What I would like to see is a 160-10 meter antenna only 130' long with a loading coil for 160 and improved power handling plus a better built box with better ventilation for moisture. The reason I dubbed this as "Wave of the Future" is because of the auto-transformer providing a high impedance to drive the antenna at the end. This isn't an "unun". It's a broadband auto- transformer and a first for the market. Others will soon follow. It goes well with my IC-7300, another wave of the future.
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