EFHW Antenna Efficiency. Just how much loss is there in this popular antenna.

Added: 2026-05-30

[00:00:00]Well, hello and welcome once again to the Waters & Stanton video channel.

[00:00:03]End-fed half-wave antennas have become very popular over the last few years, perhaps longer than just a few years.

[00:00:10]Let's just remind ourselves what an end-fed half-wave is. It's a length of wire which is resonant at a half-wave on the lowest frequency, and it has the ability to operate on harmonics above that band. And it's fed with a 49:1 unun because there's a high impedance at the end of that wire. We can then attach coax cable to it and feed that back to my transceiver. That means a 20-m length of wire would be resonant on the 40-m band and also operate on the 20, 15, and 10-m bands.

[00:00:40]And I've used one of these on and off at my home station.

[00:00:44]Well, the longest period I've used one for is about 2 years.

[00:00:49]As you know, there's there's sort of a love-hate relationship with this particular antenna. It seems to me those that have used it, the majority of them find it very good. It's very a nice antenna. It works extremely well. Uh it gives you multiband operation.

[00:01:07]And it's pretty easy to erect and take down.

[00:01:12]But there are those that really ridicule it and say, "No, it's not a good antenna. It's noisy and it doesn't work that well and it's it's not very efficient."

[00:01:21]So, what is the truth really about this antenna?

[00:01:26]>> [music] >> Well, you know, when we make comparisons with antennas, we talk about some we talk about efficiency.

[00:01:34]How well the antenna is working, how much power it actually emits, how much what what is the power that it delivers, what are the losses.

[00:01:43]You know, sometimes we can we can frighten ourselves.

[00:01:46]Um let me give you an example.

[00:01:49]If I go into a shop, I'm going to say Costa Coffee, but there are other shops. Go into Costa Coffee and I'll buy two cups of coffee and a cake.

[00:01:58]And it comes to 9.95 and uh I get my credit card out or my smartphone out and just hold it over the machine and that's it.

[00:02:07]Put it away. But if I hand over the counter a 10-lb note, and I only get 5 p change, I think, "Wow, gosh, that's expensive."

[00:02:19]And you know, it's the same price, isn't it? But it's just the fact that if you're handling cash, it seems to sort of trigger something in your brain.

[00:02:27]And you think, "Gosh, that's expensive."

[00:02:29]But it doesn't trigger the same thing in uh terms of your credit card. At least, that's the way I see it.

[00:02:37]>> [snorts] >> You know, it's the same with antennas.

[00:02:41]If I was to say, "Look, do you realize that you're losing 10% of your power? Your 100 W that you emit from your transceiver is only actually 90 W at the antenna."

[00:02:57]And you think, "Gosh, I'm losing 10% of my power."

[00:03:01]But if we relate that to dB, it's a tiny fraction of a decibel.

[00:03:07]It's the same thing, isn't it? You can get frightened over power loss, but you're reassured when you find that it's only a fraction of a dB. And I think there's some of that in antennas.

[00:03:19]We we sort of we we we fool ourselves into either thinking it's a big loss or it's a small loss.

[00:03:26]When we look at the end-fed half-wave antenna, we look at several factors. First of all, we look at what's the what's the loss on our bit of coax.

[00:03:38]What is the What is the sort of, you know, the the the basic loss of that bit of coax if it's perfectly matched? Then, we look at what's the loss on that coax if we say we get a VSWR 2:1.

[00:03:50]Generally speaking, on an end-fed half-wave, you won't get much higher than two to one, but very often you'll get it much lower than that.

[00:03:56]But nevertheless, what is the loss with a bit of coax with that sort of VSWR?

[00:04:02]And how long is that coax going to be?

[00:04:05]You know, one of the advantages of an end-fed half-wave is it doesn't need a long length of coax cuz you tend to feed it at the end, and most stations actually run a bit of coax out of the window or through the wall up to the top of the mast, connects it to the transformer. So, let's say 50 ft is probably the longest length of coax cable that most stations will use. So, it's not a long length. So, we're going to look at a 50-ft length of coax, and we're going to say, "Okay, this coax might have a two to one VSWR.

[00:04:36]Let's see what the loss is."

[00:04:39]And then, what about the unun, the transformer, the 49:1 transformer? I say 49:1 because that's the common value. Some will go higher, and some will go lower, but 49:1 is the sort of bulk standard value that most ununs are built with if they're designed to feed an end-fed wire. So, what's the loss in that unun?

[00:05:01]Now, when it comes to coax cable, it's important to get realistic about it.

[00:05:06]Remember, all coax cable has a loss.

[00:05:09]Even the most expensive cable has a loss, and the loss depends on the length and on the frequency, and of course on the type of cable.

[00:05:18]If you're thinking of upgrading your coax cable, do first of all check out what the improvement's going to be. Remember, a change of less than 1 dB is very, very small indeed.

[00:05:32]As a rough rule of thumb, 1 dB change in signal strength or power, whatever you like to call it, is just, just detectable.

[00:05:41]Anything less than 1 dB is not detectable.

[00:05:45]Now, below this video, I've a calculator. You can calculate the loss on your coax cable depending on the frequency, the length of it, and the type of cable you've got, the you know, the the reference number, RG58, 213, etc., etc. Enter those details in there, and then see what the difference in the losses.

[00:06:07]Remember that if you've got a shortish length of coax cable, which you're highly likely to have on an end-fed half-wave antenna, it may be that it doesn't justify the extra expense of buying thicker coax cable.

[00:06:21]Now, another thing to remember is that the VSWR, as it increases, so the coax loss will increase. The loss on the coax cable will increase.

[00:06:32]But, it's very, very small.

[00:06:37]The difference between a perfect match and a two-to-one match, two-to-one VSWR match, which, shock, horror, might shock some of you, is very small.

[00:06:47]It's generally far less than 1 dB, particularly on a short length of co- cable, particularly on the medium frequencies like 40 m or 20 m. You may be surprised how little change there is with that VSWR. The more important thing is will the transceiver match it?

[00:07:06]Transceivers don't like to see a high VSWR, and once they get to round about two-to-one or above, they start to close down, so you're losing power. You're not losing that power in the coax, you're just losing it because the transceiver sees that VSWR as a bit higher than it's comfortable with, and it could obviously start to damage your transceiver. Don't worry, all transceivers are pretty well protected now, but it does start to reduce the power.

[00:07:31]So, the trick here is to insert an antenna matching unit. Most modern transceivers have antenna matching units in them. Just switch that on into circuit. You'll appear to have a sort of perfect match as far as the transceiver is concerned. Won't change it on the coax cable, but the transceiver will then be quite happy to deliver full power to your coax cable.

[00:07:52]So, it's always important to check what improvement you're going to get by spending more money on coax cable whether or not even if you can't get the VSWR below about two to one whether or not you're actually going to lose that much. Sometimes you have to live with imperfection. Imperfection doesn't mean to say things don't work. And sometimes perfection for the sake of perfection just doesn't justify the extra work.

[00:08:23]So, we've talked about the coax cable and the loss in coax cable and a bit of loss when you've got a bit of VSWR, but neither of these things are very dramatic.

[00:08:35]So, let's look now at the um un-un transformer, the 49 to 1 transformer.

[00:08:42]See what sort of losses we expect there and then at the end we'll put everything together and see what realistically the efficiency is on a typical end-fed half-wave antenna.

[00:08:54]Manufacturers of 49 to 1 un-uns don't seem to publish their insertion loss figures and the frequency response, but here's a generic response based on the FT240-43 material and you'll see there's a sweet spot round about between 7 MHz and say 14 or 21 MHz. You'll also see that as we go lower in frequency, so the loss increases. Likewise, as we go higher in frequency, the loss increases. And this response curve is based on a well-matched antenna. If the SWR rises, then so would the losses increase.

[00:09:33]Now, I've put up on the screen here a chart showing typical losses you'll get on 7 MHz and 14 MHz using two different types of cable, RG58 and RG213.

[00:09:49]And I've added a two to one VSWR, which is probably um typical on the band edges.

[00:09:58]Finally, I've also added in the estimated loss on the 49 to one transformer.

[00:10:06]Remember this is on 50 ft of coax cable and as you'll see, RG58, you're going to get just over 1 dB loss.

[00:10:15]And on RG213, below 1 dB loss.

[00:10:20]And also remember this is at a two to one VSWR.

[00:10:25]If you've got a much lower VSWR, then you can see from the chart and work out yourself what the loss is. You may want to hold this video just to take a look at this chart and take it all in. Now the figures that I've just put up on the screen are based on a good installation, set up and resonant.

[00:10:45]As soon as you start to go off frequency, then not only do you get a SW loss on the coax, but you'll start to increase the loss on the actual transformer itself.

[00:11:00]And I have actually made a bit of allowance for um the transformer um assuming that you're not going to get a one to one VSWR. So I've allowed that in the figures, but if you start to go towards the band edges, two to one, and the transformer uh losses will start to increase.

[00:11:18]Now one or two things I should mention.

[00:11:20]First of all, coax losses occur in all systems. So whether you've got a dipole, whether you've got a vertical, or whether you've got an end-fed half-wave, you're going to get coax losses of the same level.

[00:11:33]The fact that you're probably going to have a shorter length of coax on an end-fed half-wave does um give it to a s- s- slight advantage in terms of losses because shorter length of coax is you get a lower loss.

[00:11:46]Now, as regards the transformer, I would encourage you to get a decent rated transformer. If you want to minimize your losses, then even if you're using a 100 W transceiver, consider getting a higher rated higher power rated end-fed uh half-wave unun because it will have heavier um windings or probably stacked uh uh ferrite cores, and altogether the losses will will uh reduce.

[00:12:15]As with any ferrite transformer, when you run low power through it, the losses diminish quite significantly. And when you run high power through it near the limit, then the losses increase.

[00:12:27]So, bear that in mind. So, I hope this video has encouraged you to uh uh give the end-fed half-wave uh uh a try if you haven't tried it.

[00:12:37]And do remember, of course, it's multi-band, and any multi-band antenna is going to have increased losses. So, whether it's a trap dipole or end-fed half-wave, you're going to lose a bit of power in the traps, etc. etc. So, it all starts to become a bit of a level playing field when you're looking at multi-band antennas.

[00:12:53]I personally like the antenna. I think it's a great antenna for beginners. I think it gets you on the air quickly.

[00:12:58]It's simple to install, and it's not that expensive. And uh it's certainly weatherproof. If If it falls down, you put it up again.

[00:13:07]It's not like a trailer where you argue with a rotator and all the other bits and pieces you have with it.

[00:13:12]And one thing I have actually mentioned before, and I'll mention it again, do use a line isolator at the shack end. Uh that's that's that's that's quite important.

[00:13:21]So, there you are. Hope it's been uh of interest to you this video, and I hope it's uh encouraged you to do some further work and experiment on antennas.

[00:13:29]And if you watch the channel regularly, why not press the subscribe button?

[00:13:33]And that notifies you when we've got new videos coming up.

[00:13:36]In the meantime, you enjoy Ham Radio. Don't forget Waters & Stanton, and we've got a great store full of gear. It doesn't matter whether you're looking for a plug or a 2,000-lb transceiver, you'll get equal service, speed of delivery, etc., etc. Don't forget we also do part exchange. We've got some great part exchange deals. And if you order on the internet, you may well find you get some better prices. Take a look at their website.

[00:14:05]There we are.

[00:14:06]You take care. Look forward to seeing you in the next video. Bye for now.

[00:14:11]>> [music]