THE UGLY BALUN choke

[Marconi]

I read your link to W8JI and that is the one that I remembered. He said what you said, and I misunderstood his words when I did the 1/4 wave model a while back. I could not model a choke anyway, and that looks to be necessary according to W8JI.

My Starduster is about 48' high, and I still use a 9' jumper inside of a little shorter mast so I can reach the connector. The connector shield of the jumper is hose clamped to this mast, and I use a barrel connector to connect to the feed line.

I don't know exactly what it does, but I don't have any TVI. I do think this setup causes the shield to see the ground at a 1/4 wave below the feed point, and maybe that helps. Maybe it even helps balance the currents at the feed point enough to mitigate the CM currents to a lower value.

 

[Marconi]

Bob, here are the 1/2 waves with 72" inch horizontal radials at 48' and 36' feet high...where you talked about the currents on a 1/2 wave or multiple length mast that is connected to the Earth.

You'll note, I didn't include the Eznec feed line feature for which...the way I was using it just seemed to confuse the issue. W8JI obviously knows better how to add the feed line to the model correctly, and he talks about how it is needed in modeling, but I don't see it included in his article you posted. So, for now I'm going to forget about this Eznec feature.

View attachment Bob's .50 wave currents idea.pdf

I would imagine the difference in results over average Earth is due to the 12' difference in height. In free space and with the mast removed, both antenna are the same, resulting in 2.02 dbi gain at 5* degrees, with an Average Gain = .0974 = 0.11db. These results should be close to what I originally posted in this thread I think on 5/19.

The models look just like you said Bob, the 36' height may need a choke if the CMC's indicates problems. However, the 36' pattern looks to me to be much more functional with its broader wave front, and maybe DX would be improved a bit, if you didn't add a choke, and the CMC's didn't present too much added noise.

I don't know if any of this could be detected just using a radio, but it is worth noting since we're talking about it. At least that is the way I look at this. I still think my suggestion still holds true according to my original posting of these models at 48' feet, where I added an overlay as the top item. I did that one with different modifications to the models, which all showed very similar patterns and gain over average Earth and including a mast in the model.

 

[bob85]

that's more like i expected with mast or feed-line current eddie,
i doubt very much you would see the difference on the s-meter, i think you would only reduce the potential for picking up noise on the mast or feed-line & rfi in the shack,

where we saw improvement we went from a no radial a99 on a bad mast/feed-line length to an isolated a99 with spiderplane or 1/4wave wire radials,
i don't know what nec would report but what we reported is what we saw in the tests and its permanent until your spiderplane breaks off in the wind

 

[Marconi]

that's more like i expected with mast or feed-line current eddie,
i doubt very much you would see the difference on the s-meter, i think you would only reduce the potential for picking up noise on the mast or feed-line & rfi in the shack,

where we saw improvement we went from a no radial a99 on a bad mast/feed-line length to an isolated a99 with spiderplane or 1/4wave wire radials,
i don't know what nec would report but what we reported is what we saw in the tests and its permanent until your spiderplane breaks off in the wind

I agree.

I will isolate the 36' foot antenna by 6" and by 108," and compare how it looks to effect the currents, pattern, match, gain, and angle.

I'll do my spiderplane model at 36' feet too. It just won't have a physical choke. Maybe we will be able to see if it really looks to need a choke.

 

[CowboyCody]

I will ask a rookie question here, all this makes me wonder what would happen to antennas like the macov5/8 or the i10k which are built with radials in mind if you isolated them from the pole. Do they figure the support and feed line in their designs?

 

[nav2010]

Look at it this way Eddie: Some people seem to think that the impedance matching section and the shunted ground is the absolute end of their antenna transmission and everything below is of no significance. Which in essence is like saying the lower radiator of a dipole isn't important providing we have a 50ohm impedance match which is bullshit.
Anyone who installs an antenna by cutting his mast at a random length, cutting his coax to a random length and provides an electrical path to both of the above without any thought must be a nut case.
But the strange thing is.....that's what most people do, which in reality is allowing their own system to determine the electrical length of the lower radiator with no input from themselves.
Isolating and choking as well as providing a resonant set of radials is akin to making sure both radiators of a dipole are balanced well and are at YOUR control.

 

[The DB]

Anyone who installs an antenna by cutting his mast at a random length, cutting his coax to a random length and provides an electrical path to both of the above without any thought must be a nut case.

I think nutcase is a bit extreme here. Uninformed would be a good word as most people that put antennas up, including many who consider themselves "techs" have no concept that either will have any effect. I would only call them nutcases if they know better and do it anyway.


The DB

 

[Marconi]

Look at it this way Eddie: Some people seem to think that the impedance matching section and the shunted ground is the absolute end of their antenna transmission and everything below is of no significance. Which in essence is like saying the lower radiator of a dipole isn't important providing we have a 50ohm impedance match which is bullshit.
Anyone who installs an antenna by cutting his mast at a random length, cutting his coax to a random length and provides an electrical path to both of the above without any thought must be a nut case.
But the strange thing is.....that's what most people do, which in reality is allowing their own system to determine the electrical length of the lower radiator with no input from themselves.
Isolating and choking as well as providing a resonant set of radials is akin to making sure both radiators of a dipole are balanced well and are at YOUR control.

Nav, we were talking about an Ugly Balun, and I raised another possible solution maybe using feed line length. I just used modeling to help demonstrate what I saw.

Bob brought up the theory or the technical aspects of feed line length to ground, and if you check close and read Bob's idea about a 1/2 wave or multiple mast length that is attached to the Earth vs. a 1/4 wave or multiple mast length that is not connected to Earth, you will see what Bob and I were getting at.

A couple have asked or presented some real world ideas in this thread, and for me your comments are always welcome, even when you get excited.

I talk about the issues that Bob mentioned, and described some differences I saw in my models, an EFHW that was connected to a mast vs. one isolated at 36' and 48' feet. However, I consider these differences noted in the models as very small, so I think they may well be insignificant in the real world.

You and Bob however, both report to have experienced differences that matter in your work on the idea of isolation. We've all heard plenty of stories that tend to report both success and failure in this regard...using radials or chokes.

My real world experiences also has not shown a difference that I could detect just using my radio. This is in spite of the fact that technically I believe there is something of benefit using the idea of isolation, with suitable radials, along with a working choke if necessary. My thinking says, it all makes sense.

I think these models do show isolation helps decouple the mast from the antenna, and that it makes a little difference that I see in the result. Because this is a small result, it seems to support my ideas on the subject. This is why I suggest the isolation idea probably doesn't really make that big of a difference in the real world. That said, I still accept the claims from you, Bob, and W8JI, saying it works and it does make a measurable difference. Believe me, if I ever experienced such differences as you guys suggest I would be in your camp too.

I have thought about what you and Bob might be experiencing however, in light of the idea that CMC's are said to increase noise on our receivers.

I think I see this very idea manifest quite often using my Starduster. It is typically a very quite antenna when conditions are quite, and this is a distinction I make in this case. Under such conditions I can usually hear some white noise on several other antennas I might have up and sometimes that noise does not present on the SD'r. In such cases I can often copy a signal that I can only hear on the other antenna.

I can imagine such events appearing as though the SD'r might have more gain and is receiving more signal, but I don't think that is possible...considering right now I have a Gain Master up a little higher to the tip. That is generally a much better antenna, and should produce more gain. I see this happen time after time locally and some times when DX is working too. Of course this could also be just a quirk with angles or locations making the difference. But you guys also have to deal with that possibility too. Personally this is one situation where the reciprocal qualities of antennas may fail...when the antenna is noisy due to CMC's.

However, I say to myself if that SD'r works that good...then who cares what the reason is, if I can hear em' I can talk to em'. I've never tested the idea, but in such cases I can imagine the other end may still see a better signal from the other antenna, but for the noise I could only hear and not copy.

 

[northern35s]

Well, I have the A99, I have the fibreglass mast, and I have my VNA, but the weather is awful, blowing a gale and certainly not the kind of weather to be messing with 18' antennas plus mast, especially with an expensive piece of test equipment attached to the base of the antenna, testing will have to wait

 

[Marconi]

Well, I have the A99, I have the fibreglass mast, and I have my VNA, but the weather is awful, blowing a gale and certainly not the kind of weather to be messing with 18' antennas plus mast, especially with an expensive piece of test equipment attached to the base of the antenna, testing will have to wait

35, your tests would be interesting, but don't do it just on my account.

I'm getting the feeling I'm wrong about radials on EFHW's being necessary for the antenna to work right or maybe even just working good...compared to what it could do if setup like Nav suggest.

I don't understand how electricity and circuits works, and I'm not sure I can ever explain my thinking about how I see an EFHW working using these models. The reason for this is, I was thinking of what Homer told me once. He said he often understands little to nothing that I post on modeling, even when I try and explain.

My common sense tell me I tend to agree with Nav's idea, it just makes sense. But, I've never experienced the big advantage that he, Bob, and W8JI see.

To the point you made earlier using an idea of a fire hose. I think we all understand basically how that works, but consider this idea.

My Eznec is showing 1 amp at 0 degrees entering the feed point of my EFHW. When I run the tabular currents log it shows the same 1 amp at the first segment, which is at the feed point. However, a few segments later, higher up the radiator the current is showing 5 amps at the segment where the maximum current is located on this 1/2 wave radiator.

How do we get this 1 amp of current coming from the feed line at the feed point to turn into to 5 amps up higher on the radiator at some point?

 

[Robb]

A network analyzer?
Kewl!

The only thing you lack for this experiment is a set of OEM radials for the A99.
Then you will be ready - IMO . . .

 

[davev8]

that will be Ohm's law then.....it must mean the voltage is changing as well...if the amps are going up the volts must be coming down
To explain... if you have say 1 amp at 24 volts you have the same power if you have 2 amps at 12 volts or 4 amps at 6 volts ...i can only assume its the same with RF as it is with electricity but as it radiates it may not be .. so your 1 amp at the feed point must be at a high voltage and as it gets more amps the volts will be coming down ..
I dont know if you have the option to display volts on the models instead of amps

 

[Marconi]

For better clarity, here is a center fed horizontal dipole that is at 48' feet, is perfectly balanced, and the current phase is turned on. This dipole may be easier to understand the currents than the EFHW. The mast is isolated from the antenna 3' feet just to show the space, but I could show this antenna model without a mast, and the balanced results we see for the radiator would still show the same exact results. I see the same results, when setting this space to 4"-6" inches too.

I also use an Eznec feature called split source at the feed point. This split source allows the feed point to be placed right at the center of the antenna, and thus we can get closer to the center than a single source will allow. The only limitation is, the feature cannot be used on wire junctions where more than two wires connect. So in this case the mast cannot be attached to this antenna, else the junction would have three wires connected, and that is not allowed.

As a result we see no currents on the mast and a perfect indication by the red line current indicator of perfect balance for the radiator. Again this model is also perfectly balanced, albeit we still see small currents on the mast. These mast currents are shown as exponential values. As an example for how much current they are, I think this equates to a value of 0.00000019 Amp for the current at segment #27 on wire #3. This wire is at the very top of the mast. These currents are also noted in the Tabular Currents Log, and they are such a small value...as to be meaningless.

Some modeler's refer to this isolation as a symbol of an effective choking device at the feed point.

View attachment Perfect Horizontal Dipole.pdf

Here are two models I did earlier of a 1/2 wave horizontal dipole at 36' and 48' feet with mast physically attached to the antenna. I suggest this 48' model will likely not need a choke if my idea about currents is close to correct.

If this doesn't help explain how I'm seeing these currents, right or wrong, then I give up.

View attachment .50w models at 36' and 48' with mast connected..pdf

 

[Marconi]

that will be Ohm's law then.....it must mean the voltage is changing as well...if the amps are going up the volts must be coming down
To explain... if you have say 1 amp at 24 volts you have the same power if you have 2 amps at 12 volts or 4 amps at 6 volts ...i can only assume its the same with RF as it is with electricity but as it radiates it may not be .. so your 1 amp at the feed point must be at a high voltage and as it gets more amps the volts will be coming down ..
I dont know if you have the option to display volts on the models instead of amps

Dave, I don't know how to show volts. They may pop up on some report, but I haven't looked. I happen to agree with your idea here, that the voltage is very high at the ends of a 1/2 wave element, etc., whether end fed or center fed.

This idea, you mentioned, does give me some ideas though, and maybe I've been wrong like I said earlier.

I'm thinking again, and that can be dangerous.

Thanks for the comments.

 

[The DB]

AC is a bit different than DC.

In an AC signal one part of the signal may have 0 amps and another part may have 5 or 10 amps or whatever up until the peak current, then it drops off to 0 and goes negative, then back to 0 and repeats itself. If you could freeze time and measure current on all of the points on a wire carrying an AC signal you would see this waveform. If you could measure voltage in the same wire at the same time you would see the same waveform. The two waveforms would be indistinguishable from each other, peaking at the same places, crossing the 0 point together, being both positive and negative together. It actually gets even more complex when talking about the antenna itself, or standing waves traveling back up a transmission line.


The DB