End Fed 1/2 wave antenna

[HomerBB]

I don't recall your answering me before regarding a some what similar idea, but I asked you what happened with your A/P when you removed the choke...that was well below the hoop by 8'-9' feet?

Do you think Bob's idea for just adding the choke 18' feet below the bottom of the A99 was similar to your thinking in that case?

I think the thread has already ventured into discussing the parts of you post I didn't quote here, but to address your question as quoted I refer you to a previous post in the thread and quote from it.

Previous Post

This is similar to what I do with the Astroplane. I advised one fellow to do this with his AP, he did not and suffered from CMC. This past Monday I helped another set up his AP at an identical height in an even more populated area. I put the coax choke 1/4 wavelength down the mast and he has had zero CMC complaints so far.

I have never run my AP in line without a choke, but my friend did.
I have only done that once when I had it on the analyzer. Never transmitted that way . . .

 

[HomerBB]

Here is the dipole setup.

Tuned for 27.4 MHz
height above ground 35' 10"
isolated from the mast
Horizontally mounted
5 wraps x 4.25" coax choke at the feedpoint
dipole tube diameter = 5/8"

 

[HomerBB]

I have read W8JI's article several times, now, and I have but one thing to submit regarding the his conclusion about the amount of gain for a dipole (I assume to be horizontal).

I know what he wrote, but exactly how/why he assigned the amount of ground gain dbi he did to the dipole is not a thing I know. Because I do not know from whence this figure came, I can not say I know it's so or not. I just know that my horizontal dipole casts a larger net and draws in a greater catch then the upright 1/2 wave was doing for the previous 2 - 3 weeks. Could simply be conditions . . .
I will try to get both up to similar heights and see, but be aware if I do, I can not use the same mast, same coax, at the same time to compare the receive and transmit to from and to the identical locations. So at least 50% of the magicians who can do that and who will read of it will not accept it no matter what.
Yes, with my tip over tower I can have the antennas switched out within 5 minutes, but I just don't think it worth all the work of running the tower up and down seeing that results in a non-identical transmission/contact comparison anyhow.

If you want to fuss at me about it go ahead. I'm good for it, and I'm equally as stubborn as the next fellow, too.

 

[Marconi]

I think the thread has already ventured into discussing the parts of you post I didn't quote here, but to address your question as quoted I refer you to a previous post in the thread and quote from it.

Previous Post



I have never run my AP in line without a choke, but my friend did.
I have only done that once when I had it on the analyzer. Never transmitted that way . . .

Yep, I remember you saying that now, but I understood that at some point you removed your choke and the questions that followed from me, was did it make any difference when you removed it.

For me, that is a bit different from anticipating a CMC, TVI problem with a buddies A/P, and installing a choke before you actually knew there would be a problem without a choke. I have never put a choke on my A/P, new or old, and the only time I had TVI was due to bad construction and loose parts. That is not very convincing to anybody, but that is all I can say.

Again, I've posted why and when I tend to see TVI with my A/P, and neither experience had anything to do with CMC's as best I could tell. It is my opinion also that the high current field surrounding the feed line and mast is adequate enough to mitigate currents below the hoop to help prevent CMC.

Homer you may remember that I did a series of models to maybe help prove the idea above could be what is going on in that area for the A/P. That is exactly what a choke is supposed to do, create a high voltage, high impedance area around a point in the system that helps curtails CMC, or like in the GM, stops it dead at just the right point to allow the antenna to work balanced per its design.

 

[Marconi]

I have read W8JI's article several times, now, and I have but one thing to submit regarding the his conclusion about the amount of gain for a dipole (I assume to be horizontal).

I know what he wrote, but exactly how/why he assigned the amount of ground gain dbi he did to the dipole is not a thing I know. Because I do not know from whence this figure came, I can not say I know it's so or not. I just know that my horizontal dipole casts a larger net and draws in a greater catch then the upright 1/2 wave was doing for the previous 2 - 3 weeks. Could simply be conditions . . .
I will try to get both up to similar heights and see, but be aware if I do, I can not use the same mast, same coax, at the same time to compare the receive and transmit to from and to the identical locations. So at least 50% of the magicians who can do that and who will read of it will not accept it no matter what.
Yes, with my tip over tower I can have the antennas switched out within 5 minutes, but I just don't think it worth all the work of running the tower up and down seeing that results in a non-identical transmission/contact comparison anyhow.

If you want to fuss at me about it go ahead. I'm good for it, and I'm equally as stubborn as the next fellow, too.

No Homer, I'm not going to fuss. If you want to test anyway you choose, is fine with me. I have faith that you will be trying your best to evaluate what you see, and let those that argue the point have their rightful say. I think I can reason with you if I have another point of view, and then two ideas are at work.

If this hadn't come up I doubt I would even be talking about TVI and CMC. TVI has not been a problem for me with my two A/P antennas. You answered that question regarding your EFHW, and that issue passed right on by. That said, I was glad to hear that Bob had successfully solved a buddies problem with TVI, even though I didn't understand his approach or idea. It seemed to be at odds with what I thought Bob would consider in previous situations, and I had a different reason for why it might be happening in his buddies case, and I showed the source of my thinking. Them guys over in England just put their antenna a little too low to suit me and that encourages TVI problems.

Haven't you worked with a horizontal dipole before? If so, didn't you see it perform in some situations that suggested that the results were sometimes amazing?

If you can, tell me what gave you the idea that your dipole had no gain?

 

[bob85]

eddie,
i am not sure but i think he originally moved the tv to get it further away from the coax/mast in an attempt to stop pissing his wife and kids off whacking the volume up and changing channel,
i know he was doing some messing with cables and foil to no avail,
after adding the choke he probably thought job sorted which is what he said about the choke, he was very happy but he did not like cables where the kids can trip over them,

after moving the tv back to the wall ( the same wall the imax is mounted on ) he found it was job not sorted, he had a face like a slapped arse after discovering he had the issue even when all the cables were disconnected and resorted to buying clamp-on ferrite for the tv mains lead which fixed the issue even when the tv was in its usual back against the wall position,

i have no idea if removing the choke will make the issue return but i will ask him to unwind it and see if the ch hopping returns, he may not want to bother but i can ask


ps, there is only one usefull method of testing antennas for those of us that don't own an antenna range,
same pole
same coax
same position
no skip
no modulation
willing and honnest helpers that are interested

signals don't change if conditions are stable, if you don't have the conditions you cannot do usefull antenna tests like it or not.

 

[HomerBB]

ps, there is only one usefull method of testing antennas for those of us that don't own an antenna range,
same pole
same coax
same position
no skip
no modulation
willing and honnest helpers that are interested

signals don't change if conditions are stable, if you don't have the conditions you cannot do usefull antenna tests like it or not.

 

[HomerBB]

No Homer, I'm not going to fuss. If you want to test anyway you choose, is fine with me. I have faith that you will be trying your best to evaluate what you see, and let those that argue the point have their rightful say. I think I can reason with you if I have another point of view, and then two ideas are at work.

If this hadn't come up I doubt I would even be talking about TVI and CMC. TVI has not been a problem for me with my two A/P antennas. You answered that question regarding your EFHW, and that issue passed right on by. That said, I was glad to hear that Bob had successfully solved a buddies problem with TVI, even though I didn't understand his approach or idea. It seemed to be at odds with what I thought Bob would consider in previous situations, and I had a different reason for why it might be happening in his buddies case, and I showed the source of my thinking. Them guys over in England just put their antenna a little too low to suit me and that encourages TVI problems.

I think you could be right. We know that TVI is an issue when RF is too close to what it is affecting.

Haven't you worked with a horizontal dipole before? If so, didn't you see it perform in some situations that suggested that the results were sometimes amazing?

Oh yeah. I am just having a little DX fun that I haven't had since I took my beam down and the conditions fell out.

If you can, tell me what gave you the idea that your dipole had no gain?

I was referencing the fact that the dipole is used as the standard for comparison for all other antenna types. I wasn't referencing the isotropic antenna to the dipole over earth.
All my antennies got gain, Pardner

 

[Needle Bender]

ps, there is only one usefull method of testing antennas for those of us that don't own an antenna range,
same pole
same coax
same position
no skip
no modulation
willing and honnest helpers that are interested

signals don't change if conditions are stable, if you don't have the conditions you cannot do usefull antenna tests like it or not.

Marconi, you completely lost me with your last two posts about my post regarding Homer's horizontal dipole ground gain.

He showed a pic of an horizontal dipole and I replied with a comment specifically referencing it, contrasting horizontal gain with that of a vertical without said gain, so I know not from whence thou cometh.

And an "AHHHH-DEEEE-OOOOH" on SSB works just fine for comparisons. Been doing it for decades, whereas FM can be a nightmare. Over the decades more than one of my rigs with FM have shown a sudden increase to full-scale with only a small amount of gain over an s-9 reading.
I would never use FM for any comparison or test, far too tempermental on the AGC & meter, far too often.

 

[Marconi]

Marconi, you completely lost me with your last two posts about my post regarding Homer's horizontal dipole ground gain.

He showed a pic of an horizontal dipole and I replied with a comment specifically referencing it, contrasting horizontal gain with that of a vertical without said gain, so I know not from whence thou cometh.

And an "AHHHH-DEEEE-OOOOH" on SSB works just fine for comparisons. Been doing it for decades, whereas FM can be a nightmare. Over the decades more than one of my rigs with FM have shown a sudden increase to full-scale with only a small amount of gain over an s-9 reading.
I would never use FM for any comparison or test, far too tempermental on the AGC & meter, far too often.

NB, I can't be for sure what I said now, and I don't want to go back and try and decipher what might have corn'fused you, but I think my main point was regarding the W8JI idea about the gain of a dipole.

Homer told us his horizontal probably had no gain, and you questioned that.

So, I looked up the source of the claim that a dipole had 8.5 db gain. I think it was Bob that first mentioned this idea to me, and it was published by W8JI.

I then modeled a horizontal 1/2 wave dipole and did a recap of the details as I raised it up 4.5' each time from 9' to 54'. I did the model with a mast that was not isolated, and a model that had no mast at all. I was thinking to compare a 1/2 strung between two trees vs. one supported on a mast with a direct connection. View attachment Eznec's idea of Homer's Horizontal Dipole..pdf

At that point in time Homer hadn't said how his horizontal dipole was supported, so I assumed it was probably isolated with PVC, but I ended up making his model grounded instead, and I discovered later that was an error.

So I messed up there.

If I could, I would do it over and delete the previous report or add a model with an isolated mast, but sometime when I make a mistake...the whole point gets lost in the added confusion trying to fix it. My whole point in doing these models was to try and prove what W8JI suggested about the 8.5 db gain using 75/80 meters. I didn't prove the 8.5 gain, but it surprised me a little that the horizontal dipole showed 7 db+ vs. about 3 db+ for a vertical dipole.

BTW, I wasn't even thinking about an isotropic comparsion like W8JI was discussing, a distinction that must be considered for his claim.

This is why sometimes trying to show evidence in support of my words can get out of hand, and then with the confusion nobody cares what the point is.

I don't know if Homer's dipole has any detectable gain or not, but he did later state his reason for saying that it had no gain. He said it was because the dipole is the standard of comparison for all antennas.

That stimulated me to wonder which dipole do we use then...as the standard, the horizontal or the vertical dipole.

We were talking about end fed 1/2 wave antennas for 11 meters, and W8JI just used the word "dipole" in his remarks, and then he showed us a model of a 75/80 meter horizontal dipole, so I was just trying to connect the dots.

I considered this recent report from W8JI needed to be fleshed out a bit, and I apparently ended up sounding like I was talking Greek.

I was also trying to discuss Bob's topic on his buddies antenna fix on a TVI problem.

Homer was talking about his end fed half wave (EFHW) which is the subject of his thread.

I was trying to talk about both subjects and then I interjected the W8JI idea. So, is there any wonder you are confused?

I'm as guilty as anybody of getting off point in these conversations at times, but that's about the state of this conversation...me thinks.

Sorry NB, but you'll just have to take your pick, and if I mis-stated anybodies postion or idea here, then I'm sorry for that too.

 

[Marconi]

Here is the dipole setup.

Tuned for 27.4 MHz
height above ground 35' 10"
isolated from the mast
Horizontally mounted
5 wraps x 4.25" coax choke at the feedpoint
dipole tube diameter = 5/8"

Homer, I've made the claim that 36' feet of mast or coax to the ground is likely a worst case scenario for CMC on several antennas I've tested with Eznec. So, you're probably right to add a suitable working choke, but how do you really know the choke is working as intended?

 

[bob85]

nb we don't have any issues with unmodulated fm, been using it for 30+ years, signals are very stable, if there is multipath fading you can hear it and thats an indication not to do any tests,
the agc works the same on any mode on a cb, not so on some hf sets especially kenwoods as they meter fm differently to the other modes and give mickeymouse signal readings.

 

[HomerBB]

I don't know whether the coax choke is working as intended or not. I always have a choke on an operating base antenna.

 

[Marconi]

I don't know whether the coax choke is working as intended or not. I always have a choke on an operating base antenna.

Well Homer that is missing my point, but it is typical for CB'rs to use a choke without knowing whether one is needed, or if it is working as intended.

Here is the idea that guides me in the use of a commom mode choke.

View attachment What Cebik says about CMC.pdf

 

[HomerBB]

Perhaps it misses your point.
1. I believe an ounce of prevention is worth a pound of cure.
2. If there is no reason not to have one there is no harm.
3. In my experience using a choke flattens the sharpness of my SWR curve. No, it does not lower the SWR on the center frequency, it causes it to be less sharp having a broadening effect.
4. No, I did not test for TVI/CMC. I simply pulled it from behind the shed in the junk pile and put it in the air so as to see if the flatside would improve my opportunities for DX.

I will go back and look for your models for a dipole at various heights. I will assume it modeled a 27 MHz dipole until I look at it.