End Fed 1/2 wave antenna

HomerBB said:

Marconi,
here are my thoughts on the 21' and 37' readings from the shack, everything else between the two readings unchanged. I speculate that the counterpoise is indeed effective on the halfwave if for no other reason but to decouple it from earth, and if so it would reduce losses to ground sometimes associated with a lack of artificial counterpoise. I think that the virtual sameness in the measurements indicates the effectiveness of the GP. So, end fed half wave antennas may very well benefit from a counterpoise/groundplane . . .

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I agree with your decoupling idea. I made a similar claim using my Eznec models, but those results were so minimal, as to likely be unnecessary. That is, unless maybe the setup was bad with TVI from mast radiation, and needed a bit more decoupling.

What do you see significant between 21' and 37' feet that leads you to your conclusion? You might disagree, but we both see similar results from your meter, but IMO that might suggest that the radials are not effective, just as well. You use the words, "artificial counterpoise" to. What does that mean?

With one exception, I think we both see very little effects, one way or another, in the match with/without radials. So, I think the only way to really tell if adding radials, makes any detectable difference is with real world performance and comparing. Are you taking any time to do and record signal reports?

The exception is, you said you were going to test by removing the radials, and that it only took just a minute or two. Have you done that since you changed the matching device?

Maybe I should reiterate, I don't think I've said an EFHW doesn't need a counterpoise of some sort in order to provide the necessary return currents. My idea is based on what Yates reported, saying the only counterpoise necessary to provide return currents...was much smaller, at .05 wavelength, than the more common idea of using full 1/4 wavelength radials near the feed point on an EFHW.

I always put it another way, without really knowing why or being able to prove the idea. It seemed to me that radials, located at the voltage node end of a 1/2 wave radiator, were not close enough to a current field to be effective for work, and thus were basically ineffective. Additionally, this is probably why I saw little to no difference on my A99 with or without radials, and arguably I'm not alone in that finding.

So, I think you should test without radials again, since you changed the matching device, if you really want to make a good comparison.

As a side note, I've had the notion that maybe this new matcher is not as effective as the older model for some reason. However, comparing that data from afar is difficult, so I'm not sure. I just had that thought at some point in the last few days analyzing your reports and since you first added the 12 radials and changed the matcher at the same time.

I think you are also seeing in your report similar trends as I have. The bandwidth and the SWR getting better with the longer feed line vs. your meter at the feed point or using a short jumper. I also note not seeing the value of X=0 over such a broad bandwidth now. Do you attribute that to getting the radials good and tight or is it that you're just recording less data points.

Regarding your comments about the repairs you made; if I found my radials loose like you describe, my experience would suggest to me I was likely to be seeing a lot of TVI/RFI interference as well. Did you notice anything before you made repairs?

HomerBB wrote

I speculate that the counterpoise is indeed effective on the halfwave if for no other reason but to decouple it from earth, and if so it would reduce losses to ground sometimes associated with a lack of artificial counterpoise.

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Spot on. Imagine how many different half waves around the world there are affected by different conductivity of soil, local geology and environment. Decouple it from that scenario and you are in much better control of your antenna.

Homer, here are a few different scenarios for what I see Eznec predicting in gain, angle, and conditions for currents on the mast. This is based on my idea of Bob's SpiderPlane at 20' using an A99.

I used 1/8" wires in the model over Eznec's idea for average Earth. I added notes to show the element lengths, and a few comments. I also added a recap for the models from my notes.

"H" = horizontal, "ISO" = isolated, "SP" = spiderplane.

View attachment Spiderplane notes..pdf

View attachment Bob's SpiderPlane idea.pdf


Edit:
Homer, maybe if you ask Nav2012 again, he'll post an image of his spiderplane, and give us some dimensions?

I know you're busy Homer, you have a life to live and a job to do, so don't let me rush you with my questions. My questions are never intended to rush you, I just wish I was up to doing some more work myself.

I had a hunch that was what you meant using the term "Artificial counterpoise," but I just wanted to make sure, I hadn't thought if it that way before.

Regarding you comparing signal reports, the traffic in this area is getting less and less all the time. Even the regulars I've talked to for years is down to less than 4, on any given day. Last year there were 9, regulars on the air almost every day, and that allowed me the chance to monitor their signals just about like I had prearranged the test, but no more, plus we have DX rolling in earlier and earlier ever week that passes by.

Regarding your fewer data points, I wasn't too sure, but your recent reports looked that way to me too.

It is never good to find bad construction issues, but it is reassuring to hear that you too had similar issues and symptoms to myself, and that most likely the loose elements produced the interference, and that you could easily detect the results with your computer speaker system. That may be helpful to some...down the road.

Take your time.

Needle Bender said:

Well Homer I've been reading around a lot, as well as a bunch of old threads here, and it just makes sense to me, but I'm not the know-all & end-all in the knowledge basket, just a learner walking through life watching & listening, trying to learn.


That's why I've devised a definitive test which will show beyond all possible questionable doubt just what that big aluminum ice cream cone really does. I kinda hope I'm mistaken about it and that the whole bloody thing radiates, making it the biggest & bestest out there, but I have my doubts.


Also, I know it takes a full additional 1/2 wave mounted at least a half wave above the first in order to achieve 2.15dB gain from a 2 element colinear array and there's only a possible additional 1/4 wave below the top 1/2 wave on the vector, so there's nowhere near enough antenna nor element spacing to provide colinear gain of more than a small fraction of a dB, if that was how it operated.


Makes sense that it's simply a full 1/2 wave with the same 1/4 wave null below it that the end-fed 5/8 also has, helping it to achieve a lower TOA like the 5/8, except with 33% - 1dB more radiator.


Again, it's only my best guess and I'll know for certain once I get the test completed. :mellow:


Bob, like you, I just gotta try it for meself

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NB, you promised to post your conclusive results on how the Vector really works noted in bold above. It has been almost two weeks since you promised some evidence, beyond all possible questionable doubt.

How are you progressing with that idea?

HomerBB said:

21' and 37' are simply my minimum and maximum heights above the earth for the analyzer readings. You have done some incremental modeling at various heights so I thought you might want to compare the actual readings of my 259b to your hypothetical models. Also, it is a reasonably common occurrence when raising antennas to see band center movement..............

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Homer, I would love to be able to compare your real world testing of your tuned EFHW, but I can't model the matching device required, thus my models show a very bad match in such cases. So, I have nothing to compare. Do you think such a difference in match would make a big difference to gain and angle for a model?

I also agree it is natural to see resonance change as antennas are raised higher.

Independence ain't SW, Homer. . Hope to catch you out there.

Hey Homer, when are you going to try building a horizontal Delta Loop beam?

I've thought about building one in the horizontal polarization then running an A99 up through the middle about 3" from the driven element so it might pick up vertical polarization and sympathetically radiate both polarizations in phase to help get rid of selective fading.
I'd use a couple 1/4 waves of 75ohm rg11, one to each antenna, to a T connector and then my 50ohm coax from there down.

If I beat you to it I'll let you know how it works when we QSO again on L38

HomerBB said:

I don't know. The only way I have to compare TOA is to try to compare the differences in local to distant local signals. The problem is, I have no way of knowing when someone will be on the band.
Saturday night after skip dropped out I had some great contacts in to Missouri and Oklahoma. One was roughly 38 miles, and the other nearly 35 miles distant. Not much, I know, but the ease of communications was remarkable for my QTH. I could only wonder if it was those sweet conditions that often follow a bout of DX, or improvement in my antenna setup.

I wish I had a more reliable method of comparison.
I guess I'm gonna have to get my ticket so I can make these antennas for other bands in order to put some Hams in the area to work on these things with me.

I will be out of town Wed thru Sunday this week. All I'm taking for antennas is a dipole, and my EFHW wire antenna,

I strung this up above the house today and left the tap where my analyzer had promised a match. The SWR meter dropped right down to 1.0:1 on the frequency. think this will be fun for a change. Listen for Homer out of SW Kansas this week.

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I'm using one of these antennas that Homer made and gave to me. It is now in my back yard, strung horizontally from the eve of my house to the edge of my shack. It is only about 10 feet off the ground, and barely visible. Works surprisingly well both for local and dx work!

73,
RT307