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Amateur Radio Antennas - For discussion of all amateur band designed antennas and related accoutrements. This includes base, handheld, mobile and repeater usage. For commercial antennas on the amateur bands please use Commercial Radio Antennas below.

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Old 08-06-2017, 8:10 AM
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Default MyAntennas EFHW-8010

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Originally Posted by prcguy View Post
I've used lots of wire antennas in my time and have settled on the Myantennas EFHW-8010 as my primary HF home antenna.
I'm intrigued by the MyAntennas EFHW-8010P. This is the 200 watt version that uses 18 gauge wire. I considering this antenna for portable operations where I'd be setting up a temporary station in a public park. The set-up would be by myself, so I'm looking for options where I'd be able to set up an antenna without a tremendous amount of effort. I've used dipoles and off-center fed antennas, but never an end-fed.

If I understand the layout of the EFHW-8010, you have the balun in a fixed location and the coax from the radio attaches to the balun. Running out of the balun is 130 feet of wire. But, how does that wire need to be arranged? Does one end of the wire have to be high off the ground? Does the center of the wire have to be high off the ground? Does the balun require any kind of counterpoise? Do you have to lay out a ground wire?

Since you have experience with the EFHW-8010, I'm hoping you can help. Thank you.
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Old 08-06-2017, 10:26 AM
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The resonant EFHW is not much different than a center fed dipole of the same length except you are exciting it from one end. Put it horizontal at 20 to 30ft off the ground and it will be a great NVIS antenna on 80 and 40m but will also make DX contacts there. It will have a lower angel takeoff on 20m if its 1/2 wave off the ground like 33ft. If you have the transformer low to the ground and one end up high it will degrade low angle performance just like a dipole and NVIS on 40 and 80m will get quieter on receive with less signal out, etc.

The transformer is broad band 80 through 10m and you can attach 1/2 wavelength of wire for any band and it will also work harmonically related bands. That means you can substitute the stock 133ft of wire with 65ft and now its a 40/20/15/10m antenna. Use 33ft and now its a 20 and 10m antenna and short enough to hang vertically on a fiberglass pole.

I've been using a home made 40/20/15/10m version for camping and park use for many years. It handles up to 100w, the transformer is a little bigger than a Zippo lighter and all the wire and guy string wind up into a gear driven plastic chalk line reel. You can make the whole thing for less than $20 and if you don't use a chalk line reel its only about $10.
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Originally Posted by W9BU View Post
I'm intrigued by the MyAntennas EFHW-8010P. This is the 200 watt version that uses 18 gauge wire. I considering this antenna for portable operations where I'd be setting up a temporary station in a public park. The set-up would be by myself, so I'm looking for options where I'd be able to set up an antenna without a tremendous amount of effort. I've used dipoles and off-center fed antennas, but never an end-fed.

If I understand the layout of the EFHW-8010, you have the balun in a fixed location and the coax from the radio attaches to the balun. Running out of the balun is 130 feet of wire. But, how does that wire need to be arranged? Does one end of the wire have to be high off the ground? Does the center of the wire have to be high off the ground? Does the balun require any kind of counterpoise? Do you have to lay out a ground wire?

Since you have experience with the EFHW-8010, I'm hoping you can help. Thank you.
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Old 08-06-2017, 10:44 AM
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It was my understanding that the EFHW-8010 and EFHW-8010P were multi-band antennas and there would be no need to change out the radiating element for different bands. Is that not the case?

I assume that there are high voltage nodes along the wire. What parts of the wire might I need to protect from people getting too close?
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Old 08-06-2017, 10:52 AM
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Yes, but sometimes you only need to use 20m or 10m and you have the option to shorten the antenna for higher bands so it might fit where 133ft will not.

Just like a dipole of the same length operated on multiple bands, there will be high voltage at the ends of a half wave or multiples of a half wave. For the 133ft version the high voltage would be at each end on 80m. On 40m that would be at each end and in the center. On 20m that would be the ends and two equally spaced high voltage points across the middle, yada, yada.

The transformer is about 64:1 ratio matching your 50 ohm coax to about 3,200 ohms which is ideal for the end of a half wave antenna.
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Quote:
Originally Posted by W9BU View Post
It was my understanding that the EFHW-8010 and EFHW-8010P were multi-band antennas and there would be no need to change out the radiating element for different bands. Is that not the case?

I assume that there are high voltage nodes along the wire. What parts of the wire might I need to protect from people getting too close?

Last edited by prcguy; 08-06-2017 at 11:00 AM..
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Old 08-06-2017, 1:27 PM
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I see your point about using a shortened version when situations warrant.

What about grounding or a counterpoise? I saw some YouTube videos about this antenna where they were using a wire from the ground terminal on the transformer to a ground rod. Is this necessary? What happens to performance if you don't have a ground or counterpoise?
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Old 08-06-2017, 2:53 PM
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The resonant EFHW does not require a counterpoise or grounding of the transformer as observed in countless installations. In my experience, at resonance there is no measurable RF on the coax but when you get to the band edges or out of band the coax will start to light up with common mode RF. Its a really good idea to place an effective common mode choke in the coax close to the transformer to eliminate any problems.

It just happens that MyAntennas makes the most effective 1:1 choke baluns I've seen advertised.

There has been some analysis that suggests at least a small counterpoise of at least.02 wavelengths is needed and I think a short length of coax between the transformer and choke balun should easily satisfy that. Otheriwse I would ground the antenna or coax at some point to meet NEC.
prcguy

Quote:
Originally Posted by W9BU View Post
I see your point about using a shortened version when situations warrant.

What about grounding or a counterpoise? I saw some YouTube videos about this antenna where they were using a wire from the ground terminal on the transformer to a ground rod. Is this necessary? What happens to performance if you don't have a ground or counterpoise?
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Old 08-06-2017, 3:51 PM
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If your still not sold I can loan you a home made 100w 40-10m version for a week.
prcguy
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Old 08-06-2017, 4:49 PM
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Thanks for the offer. I think I'm sold on the idea. Just need to fit it into my budget for both time and money. This would be strictly for portable operations--an afternoon in the park sort of thing. I'm pretty happy with the dipoles I have at home.

Thanks for the feedback!
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