EFHW 49:1 placement

[KK4IXETerry]

When installing a EFHW will it preform better with the 49:1 elevated or closer to the ground? I asking in regards to a sloper configuration.

Kk4ixe
Terry
73’s

 

[K6GBW]

There are several ways to set up an EFHW. None are "better" than the other, but they are different depending on what you want the antenna to do. The antenna primarily radiates from the center of the wire for the primary band it is made for. So if it is a 40 meter EFHW will radiate from the center of the wire. If the tranformer is elevated and the wire slopes down you can visualize the wave propigating slightly in the direction it slopes toward. If you mount the transformer near the ground and string the wire upward it is the same. If you place the transformer up high and run the wire perpendicular to the ground the wave acts just like a dipole hung in a similar fashion. The advantage of placing the transformer low is that you can easily ground it to a ground rod and if you hang it high then the coax that hangs down will radiate somewhat. If you operate the antenna on any band above the primary base band then it develops additional lobes. So at 20 meters a 40 meter EFHW would have two lobes. The EFHW is influenced by its height above ground just like a standard dipole, so if it is down below a half wave height the pattern will become more NVIS. As you can see, it's a very versitile antenna and it can be deployed a number of ways. It just depends on what you want it to do and what you are able to do.

 

[merlin]

You might consult the ARRL Antenna book. The section on EFHW wire antennas has some good diagrams that will help you understand the characteristics if this antenna.
K6BGW gives a good brief overviw, I can't add to that.

 

[KK4IXETerry]

There are several ways to set up an EFHW. None are "better" than the other, but they are different depending on what you want the antenna to do. The antenna primarily radiates from the center of the wire for the primary band it is made for. So if it is a 40 meter EFHW will radiate from the center of the wire. If the tranformer is elevated and the wire slopes down you can visualize the wave propigating slightly in the direction it slopes toward. If you mount the transformer near the ground and string the wire upward it is the same. If you place the transformer up high and run the wire perpendicular to the ground the wave acts just like a dipole hung in a similar fashion. The advantage of placing the transformer low is that you can easily ground it to a ground rod and if you hang it high then the coax that hangs down will radiate somewhat. If you operate the antenna on any band above the primary base band then it develops additional lobes. So at 20 meters a 40 meter EFHW would have two lobes. The EFHW is influenced by its height above ground just like a standard dipole, so if it is down below a half wave height the pattern will become more NVIS. As you can see, it's a very versitile antenna and it can be deployed a number of ways. It just depends on what you want it to do and what you are able to do.

Thank you

 

[KK4IXETerry]

You might consult the ARRL Antenna book. The section on EFHW wire antennas has some good diagrams that will help you understand the characteristics if this antenna.
K6BGW gives a good brief overviw, I can't add to that.

Thank you

 

[KK4IXETerry]

There are several ways to set up an EFHW. None are "better" than the other, but they are different depending on what you want the antenna to do. The antenna primarily radiates from the center of the wire for the primary band it is made for. So if it is a 40 meter EFHW will radiate from the center of the wire. If the tranformer is elevated and the wire slopes down you can visualize the wave propigating slightly in the direction it slopes toward. If you mount the transformer near the ground and string the wire upward it is the same. If you place the transformer up high and run the wire perpendicular to the ground the wave acts just like a dipole hung in a similar fashion. The advantage of placing the transformer low is that you can easily ground it to a ground rod and if you hang it high then the coax that hangs down will radiate somewhat. If you operate the antenna on any band above the primary base band then it develops additional lobes. So at 20 meters a 40 meter EFHW would have two lobes. The EFHW is influenced by its height above ground just like a standard dipole, so if it is down below a half wave height the pattern will become more NVIS. As you can see, it's a very versitile antenna and it can be deployed a number of ways. It just depends on what you want it to do and what you are able to do.

Thank you, this helps a lot.

 

[AC9KH]

If the antenna is a sloper, if it was me I'd put the matching transformer close to the ground. The shorter the wire run to the ground rod the better it is. And if you don't use a ground rod, well, that's another topic. Just make sure it's safe. The feedpoint voltage of an end-fed half-wave antenna is quite high and if somebody accidentally touches it they won't forget the experience any time soon.

 

[prcguy]

In my opinion you get the most out of an EFHW or OCFD or most any multiband wire antenna when horizontal at about 30-33ft above ground. That will provide the most gain in NVIS mode for 80/40m and its at the first half wave height for the lowest angle of radiation for 20 and 10m. Lower the antenna and you start loosing low angle takeoff on 20m and you loose efficiency in NVIS mode on 40/80m.

Raise it higher and you start loosing NVIS on 40m and so on but you can get it to the first half wave point on 80m which is about 133ft high and have a great low angle takeoff on all bands but with no NVIS. I think it will be most efficient horizontal rather than sloped unless your trying to peak some directional characteristics off the end on the higher bands.

I've used EFHWs in all kinds of places sloped, horizonal, laying on the ground, you name it but mostly when camping for temporary use.

 

[AC9KH]

Some people are big into NVIS, other's aren't. I have a 127' vertical EFHW with a full ground plane under it with 34 in-ground radials. I switch the transformer primary out for 160 and convert it to a 1/4 wave Marconi. That's pretty hard to do with a horizontal wire. While the antenna works on 40m, it's not great. I got shorter antennas for that. However, it does work awesome on 60m (with the transformer primary switched out) as a 3/4 wave vertical.

 

[AC9KH]

Actually, the question here was not the wire orientation. The question was, is is better to put the transformer closer to the ground or up in the air? My answer is, as close to the ground as possible, as long as it's safe and nobody is going to touch it. Anything feeding that transformer will radiate up to the point where it's terminated at ground. The shorter that run is from the transformer to RF ground, the better the antenna works, regardless of the wire orientation. @K6GBW covered this fairly well. Yes, the antenna is electrically complete and will have the same radiation pattern as a dipole regardless of wire orientation. But the EFHW is not a dipole. It is an unbalanced load being fed against earth ground. Some people have tried to use them without a ground rod and everything in the shack is hot because the other half of the circuit is looking for that earth ground. This is a problem that a dipole does not have because it's a balanced load.

So the transformer does two things;
- it's a voltage step-up transformer and it produces high enough voltage to force current into an extremely high impedance load
- in the process it transforms the impedance down to something that your tuner can handle

If you look at the circuit of the transformer, in this case an autotransformer configuration where the ground is on the right in the photo and the antenna connection is on the left, the RF ground is an integral part of the antenna system. It is DC connected directly to the antenna itself.



So that ground radiates up to the point where it is terminated at earth ground. This is undesirable because it reduces the efficiency of your antenna system. The sooner you can terminate that ground side, the more efficient your antenna will be. If you fail to terminate that RF at earth ground, your coax shield, radio and anything connected to it will try to take its place. Yes, you can put a RF choke inline to try to keep common mode off your radio gear, but that still doesn't take the place of the earth ground that the antenna requires to be efficient.

The upside to properly grounding an EFHW is that it is a DC grounded antenna, making it quieter with better S/N in static conditions from wind and rain vs a dipole. The quicker you can get the transformer to that RF ground, the better it is. Just make sure it's high enough to be safe because you can jump a 1/2" air gap off the high voltage side of that transformer even at moderate power levels.

 

[prcguy]

Actually, the question here was not the wire orientation. The question was, is is better to put the transformer closer to the ground or up in the air? My answer is, as close to the ground as possible, as long as it's safe and nobody is going to touch it. Anything feeding that transformer will radiate up to the point where it's terminated at ground. The shorter that run is from the transformer to RF ground, the better the antenna works, regardless of the wire orientation. @K6GBW covered this fairly well. Yes, the antenna is electrically complete and will have the same radiation pattern as a dipole regardless of wire orientation. But the EFHW is not a dipole. It is an unbalanced load being fed against earth ground. Some people have tried to use them without a ground rod and everything in the shack is hot because the other half of the circuit is looking for that earth ground. This is a problem that a dipole does not have because it's a balanced load.

So the transformer does two things;
- it's a voltage step-up transformer and it produces high enough voltage to force current into an extremely high impedance load
- in the process it transforms the impedance down to something that your tuner can handle

If you look at the circuit of the transformer, in this case an autotransformer configuration where the ground is on the right in the photo and the antenna connection is on the left, the RF ground is an integral part of the antenna system. It is DC connected directly to the antenna itself.

View attachment 200308

So that ground radiates up to the point where it is terminated at earth ground. This is undesirable because it reduces the efficiency of your antenna system. The sooner you can terminate that ground side, the more efficient your antenna will be. If you fail to terminate that RF at earth ground, your coax shield, radio and anything connected to it will try to take its place. Yes, you can put a RF choke inline to try to keep common mode off your radio gear, but that still doesn't take the place of the earth ground that the antenna requires to be efficient.

The upside to properly grounding an EFHW is that it is a DC grounded antenna, making it quieter with better S/N in static conditions from wind and rain vs a dipole. The quicker you can get the transformer to that RF ground, the better it is. Just make sure it's high enough to be safe because you can jump a 1/2" air gap off the high voltage side of that transformer even at moderate power levels.

Most EFHW antennas using a 49:1 or 64:1 transformer are a nearly complete antenna not requiring a ground or counterpoise, not counting the coax. They will radiate very similar to a dipole of the same length. So put the entire antenna up in the air along with the transformer, it doesn't need to be grounded or be close to the earth.

 

[AC9KH]

Unfortunately, I'm going to disagree. Other than loops, all antennas are dipoles whether you intend them to be or not. All antennas require some return path for the RF current. In a balanced center-fed dipole or a loop this is inherent. That’s why you don’t need a ground connection or counterpoise when using a balanced antenna except for static/lightning purposes.

When using unbalanced end-fed antennas like mobile whips, verticals, random wires, rubber ducks and EFHW's, we need some form of a return path. With mobile whips you have the car body. Verticals use radials or ground screens. A little HT uses you as the counterpoise. Some people claim that you don’t need a ground or a counterpoise for an EFHW. Not true. You’re getting one, regardless. It's basic AC circuits. If you don't provide that proper ground It’s the outside of your coax shield. If you’re lucky your coax feedline is the correct length to act as the counterpoise for that band. If not, you get variable tuning, poor performance, and in some cases RF burns off your equipment.

To each his own. But declaring that a EFHW does not need a ground or counterpoise is simply dead wrong and a basic misunderstanding of AC circuits. An EFHW can no more function as a standalone wire than a basic 120V AC house circuit can using only a "hot" with no neutral. There is no "magic system" where you feed power into a wire and get any current to flow in it without completing the other half of the circuit. Period. When dealing with RF and high voltages, it can become dangerous. Please don't mislead people into thinking otherwise.

 

[prcguy]

Unfortunately, I'm going to disagree. Other than loops, all antennas are dipoles whether you intend them to be or not. All antennas require some return path for the RF current. In a balanced center-fed dipole or a loop this is inherent. That’s why you don’t need a ground connection or counterpoise when using a balanced antenna except for static/lightning purposes.

When using unbalanced end-fed antennas like mobile whips, verticals, random wires, rubber ducks and EFHW's, we need some form of a return path. With mobile whips you have the car body. Verticals use radials or ground screens. A little HT uses you as the counterpoise. Some people claim that you don’t need a ground or a counterpoise for an EFHW. Not true. You’re getting one, regardless. It's basic AC circuits. If you don't provide that proper ground It’s the outside of your coax shield. If you’re lucky your coax feedline is the correct length to act as the counterpoise for that band. If not, you get variable tuning, poor performance, and in some cases RF burns off your equipment.

To each his own. But declaring that a EFHW does not need a ground or counterpoise is simply dead wrong and a basic misunderstanding of AC circuits. An EFHW can no more function as a standalone wire than a basic 120V AC house circuit can using only a "hot" with no neutral. There is no "magic system" where you feed power into a wire and get any current to flow in it without completing the other half of the circuit. Period. When dealing with RF and high voltages, it can become dangerous. Please don't mislead people into thinking otherwise.

Talk to Danny Horvat, the engineer behind MyAntennas and he designed a number of antennas for Cushcraft. He has sold 10s of thousands of EFHW antennas and will tell you what I said, the antenna doesn't require any grounding to work and grounding it won't necessarily make it work better. It will have some effect on the radiation pattern but that may be better or worse for what you need. There is stray capacitance within the transformer that satisfies most of the RF current return and at best it needs at least a .02 wavelength "counterpoise" but that is always supplied via the feedline. Within its resonant bands there is no perceivable RF on the coax.

It doesn't need a counterpoise beyond a few feet of coax and I have run them with just a few feet of coax then to a very good 1:1 choke balun with no difference in SWR or performance. Grounding may be required on the feedline where it enters a building to meet code but the antenna doesn't care. Its otherwise self contained so put the entire antenna including the transformer up in the air and its recommended to use a choke balun somewhere in the coax as operating the antenna out of band can light up the coax with RF.

A 64ft 40m version will radiate nearly identical to a center fed 1/2 wave 40m dipole so install it like you would a dipole. The heights I recommended in post # 8 are well known for dipoles, wire antennas, Yagis, etc, and I have proven that out in the last 45yrs of playing with antennas.

This is one of the cases where theory doesn't agree with real world as much of the theory is misunderstood on these. Many people have argued about the EFHW and how it can't work without this or that, then Danny Horvat enters the conversation and puts it all to rest. Nobody has built and sold more EFHWs than him and the antenna speaks for itself. Just put it up and let it speak and stop worrying about things that don't matter.

 

[prcguy]

BTW, the windings in the transformer in post 10 don't look quite right for an EFHW transformer, what's the turns ratio on that thing? The two turn primary is usually a twisted pair to improve coupling. There should be about 14 turns total including the first two turns of twisted pair and its proven best to cross over the windings about half way through which helps isolate the very high impedance output from the input.

This is much more typical of an EFHW transformer, although this one has multiple cores for higher power handling.

 

[AC9KH]

BTW, the windings in the transformer in post 10 don't look quite right for an EFHW transformer, what's the turns ratio on that thing?

It's not the same thing as you're using. It's an autotransformer with a switching relay to switch out the tap. It is designed specifically for 160, 80 and 60 meters with a 127' vertical with 34 in-ground radials. The autotransformer tap is only used for 75/80.

 

[AC9KH]

Talk to Danny Horvat, the engineer behind MyAntennas and he designed a number of antennas for Cushcraft.

This would be the fellow that sells a $27 antenna to unsuspecting hams for almost $200? Then says if the box is high in the air don't bother grounding that - ground the coax instead? And it has to be fed with 50ft of RG8? So in reality, he's using the coax shield for the counterpoise?

There are some people that are gullible.

So, I think I'll pass on that one. There's people on the internet selling snake oil all the time. I don't care if you're Danny Horvat or Elon Musk, any end-fed antenna needs a return path to ground or it won't work. Period. If you don't ground the box or the coax, it will be grounded thru your station safety grounds. And good luck with that.

Edit: and if you're operating portable with a battery and no station safety ground, don't touch the radio when it's hot or you'll learn all about grounding.

 

[K6GBW]

Love these conversations. It's like watching Mexican wrestling!

 

[prcguy]

This would be the fellow that sells a $27 antenna to unsuspecting hams for almost $200? Then says if the box is high in the air don't bother grounding that - ground the coax instead? And it has to be fed with 50ft of RG8? So in reality, he's using the coax shield for the counterpoise?

There are some people that are gullible.

So, I think I'll pass on that one. There's people on the internet selling snake oil all the time. I don't care if you're Danny Horvat or Elon Musk, any end-fed antenna needs a return path to ground or it won't work. Period. If you don't ground the box or the coax, it will be grounded thru your station safety grounds. And good luck with that.

Edit: and if you're operating portable with a battery and no station safety ground, don't touch the radio when it's hot or you'll learn all about grounding.

I've got probably hundreds of hours operating battery portable and even at the 100w level with ungrounded EFHWs and no hot coax. I'll even stick my tongue on the transformer coax connector to prove it. Your making stuff up that doesn't apply and an EFHW made by most of the major mfrs do not need grounding of any type to perform and grounding will not make them perform better. Grounding will change the radiation pattern a little but only due to the proximity of the new wire in the circuit but that's it. Been there and done that over and over.

I've also seen this argument many times online and usually by people that have never used the antenna ungrounded, they just keep posting without ever understanding or testing it. I've also seen them humbled by Mr Horvat when he explains the theory and addresses the wrong assumptions people make that they can never prove.

Instead of spreading nonsense why not test an EFHW with or without ground and see what happens. I dare you to put one up vertical, with transformer 6ft off the ground, take precise field strength measurements then ground it to a ground rod and take field strength measurements again. You wont see more than a tiny difference and it may even get worse.

Lets ask if anyone else is out here using an EFHW and it had problems ungrounded and grounding fixed or improved something.

 

[prcguy]

Love these conversations. It's like watching Mexican wrestling!

Who has the best Lucha Libre mask?

 

[AK9R]

Love these conversations. It's like watching Mexican wrestling!

It's like having two mature bulls. They snort, paw at the dirt, butt heads, and push each other with all their might until one gets tired and walks away.