THE UGLY BALUN choke

[Marconi]

i only saw a few needle-widths change when comparing the gainmaster to my i-10k to everybody but one friend who noted if i recall correctly a couple of s-points drop when i swapped from the 10k to the gainmaster and back up again when i swapped back on his ft897 meter,
between imax and 10k we had 1.5 s-units to one guy and more to another friend,
i put it down to the imax not been happy on the same pole as the i-10k, not that the 10k had that much more gain,

if you can't make cm currents look bad with any length mast or feedline i don't know whats going on with the model, i know you can have enough current on the coax to cause bad rfi in the shack with an a99, isolating and adding radials cured it, the same is true with the imax.

Bob, it's not that I can not make CMC's look bad with any length mast or feed line, I wasn't trying to deal with changes in height or feed line length in this idea. I was trying to demonstrate why I think radials may not matter with an EFHW radiator, but maybe it is just a technical difference, and it may not matter as much in a real world setup. I'm also not saying I think it is a good idea either. That said, I've also noted that I see adding radials to the EFHW model does show there is improved decoupling. But according to these models and some of my real world testing the idea, it does not look to change the gain or angle much, at least as best I can tell, but truthfully I can't measure either...I just have to go by what I see from my radio.

I've been saying for some time as a result of my using Eznec, that I see some feed line lengths...ill-effecting results. I still don't know if that effects all the different CB antennas we might talk about here, but I was suggesting that maybe it could help to mitigate bad CMC effects just by a change in the feed line length.

I might have suggested in my earlier posts that the cause of this was height rather than feed line length, but that was simply because at the time I was using the mast as a reference to the length of the feed line. So in such cases, if I changed the mast length the antenna height and the feed line length also changed.

Now that I have figured out a way to use the Eznec transmission line feature I can change the feed line length without changing the antenna height. I hope this makes sense as to why I was saying height rather than feed line length, and that I said it clearly.

Here are two models, one at 36' that I just did, and the other I posted the other day at 48' feet high. I'm not 100% sure, but I think all I changed was the height of the antenna, so we can see what happens when, as you suggest, using a 1/2 wave multiple mast connected to the ground.

View attachment Bob's follow up.pdf

Form the looks of this the radials, mast, and feed line has sucked almost all of the RF out of the radiator. To me this looks like a 36' tall mast with a load on top. You can see in the currents log that the currents on the mast, feed line, and radials are much greater than those on the radiator.

Except for the part about radials, I think this fits W8JI comments in the following link where he describes a similar situation with the Imax/A99 and the mast radiating as much as the part on top that we think is the antenna. Scroll down to the Imax/A99 topic.

End-fed Vertical and J-pole

 

[bob85]

eddie, i have no idea why you have little current on the radiator in the second model,
if the model is correct you would see the difference between the two,

before mm2000 did the isolation/spiderplane setup on his a99 he would always struggle to hear my buddy "thecobraman" when i talked to him,

after the isolation he could hear him no problem with improved signal strength in both directions,
recently his spiderplane broke off in high winds, surprise surprise he struggles to hear thecobraman again,

that and several other before/after reports from trusted friends tells me his isolation worked for his situation mast/coax length as it did with the two sloping 1/4wave wires for another friend with the same results,

it also indicates to me that isolating the mast and adding a choke won't work without radials or some form of counterpoise for return currents as w8ji & kirchhoff claim,

the radials need not be 1/4wave to give some benefit,
some say the solarcon radials are useless, we find that is not true in our tests on a99 or imax if the antenna is isolated from any conductive mast and choked, significant reduction in rfi and some improvement in signal/reduction in noise can be had ( with some mast/coax lengths )

my guess is the people who denigrate the solarcon radials did not isolate the antenna correctly or did not have cm issues to start with,
fork handles or fiberglass tube can work,
just insulating the mast forming a capacitive coupling probably won't work,

thanks for the 1/2wave multiple mast model

 

[Marconi]

I mess up Bob.

If you look at the first model of the last two that I posted above just yesterday, you'll see that I hand wrote a caption correction for the title of the model on top of the pdf file. That means I noticed a mistake in the caption, and that I forgot to change the title and save it, else I would have used the saved and corrected file.

This has happened to me before, and now I'll have to reconstruct the model and the idea, but that should be easy if I haven't changed the file in some other way. That is the problem with not saving the work and Eznec works good to keep me form doing just that, but I just ignored the warrning I'm sure.

I remember last night that I saw the captioned title on the first model noted as (.50w EF no radials 48') and the name was in error. The model had radials and the caption showed no radials. I corrected the model the wrong way by writing "with 4x72" and crossing out the word "no." I should have gone back, changed the caption and saved it right, but I was dead tired.

This is also when I had the thought about my getting confused, and I think I posted that last night too. I decided to wait until today to post your idea that hopefully would produced more CMC's by changing the height.

I got up today, and posted the file as it was, without even looking back. I did not fix the model's caption nor save that file.

Sorry.

 

[Marconi]

I mess up Bob.

If you look at the first model of the last two that I posted above just yesterday, you'll see that I hand wrote a caption correction for the title of the model on top of the pdf file. That means I noticed a mistake in the caption, and that I forgot to change the title and save it, else I would have used the saved and corrected file.

This has happened to me before, and now I'll have to reconstruct the model and the idea, but that should be easy if I haven't changed the file in some other way. That is the problem with not saving the work.

I remember last night that I saw the captioned title on the first model noted as (.50w EF no radials 48') and the name was in error. The model had radials and the caption showed no radials. I corrected the model the wrong way by writing "with 4x72" and crossing out the word "no." I should have gone back, changed the caption and saved it right, but I was dead tired.

This is also when I had the thought about my getting confused, and I think I posted that last night too. I decided to wait until today to post your idea that hopefully would produced more CMC's by changing the height.

I got up today, and posted the file as it was, without even looking back. I did not fix the model's caption nor save that file.

Sorry.

 

[bob85]

no worries eddie, we all make mistakes, i was more interested in the 1/2wave multiple grounded mast,
i don't understand why its showing much more current in the mast than the radiator

 

[Marconi]

no worries eddie, we all make mistakes, i was more interested in the 1/2wave multiple grounded mast,
i don't understand why its showing much more current in the mast than the radiator

Bob, this is the first time I've seen that too.

Yesterday when I saw those results you noted above, I thought about what W8JI said in one of his Imax articles. So, I figured what I saw might be suggesting the idea he was talking about. I did not remember all the details, but I know now that he was talking about an Imax, and it showed a good current flowing in the radiator too. I was also thinking it was like a dummy load up there.

I found the file that I added the radials too, at least it is the file with the same captioned name we see in the pdf I posted. But, it does not look to be the same file when I print the Antenna View or the Currents Log. The gain and angle are the same as in the Pattern View, but the currents are quite different.

Besides these differences, the concern I have is this file prints the caption for the Antenna View in a much larger font size, and I don't understand that. To change the font and the size of the type requires one to access a particular area, make the selections, and save the change. I have not done that in a long time. In the beginning I did change the default size from the large font size to a small font size...in order to save ink. This changed on me unexpectedly.

I have been unsuccessful today in duplicating this effort. The gain and angle are the exact same, but the current data does not agree with what I posted this morning. I'll have more time tomorrow maybe.

I have it when I make a file and forget to save it. These are the very ones I'll get questions on, and I can't easily see what I've done later. I told you I needed to slow down a bit, too many keys being pushed and to many ideas going on.

I will try a different file and see if I can duplicate the work. If it does not duplicate...then some how the first models were obviously incorrect.

Thanks for calling my attention to this seeming error at this point. I'm sounding like a politician now, trying to get my story straight.

I always figure if we can't duplicate something...then what we had originally done was no good.

 

[W5LZ]

That mast, or anything else that's a 1/2 wave or a multiple of one will show more -induced- currents than some conductor that's not a 1/2 wave length. Same reason why guy wires of particular lengths are not recommended.
- 'Doc

 

[Marconi]

"Doc, I think we all might agree that Bob's suggestion here is likely true. You just confirmed the idea.

I wanted to model Bob's idea, but when I posted the models Bob had a question and his question made a lot of sense, but I had no answer unless maybe I went back and checked the models.

All I was trying to do, in this case, was added radials, change the height from 48' to 36' feet, Bob's idea for a 1/2 wave multiple mast length, and post the results.

Bob, I know now what I did wrong. I first selected a model to demonstrate the results for your suggestion...to change the height and use a 1/2 wavelength, or multiple, for a mast that was grounded.

I mistakenly selected a model to modify that was isolated (ISO). It was in fact the same model that I had earlier only isolated by 1" inch and I talked about it in this thread. That is the one where I had to change to 12" inches.

With my poor eyesight I just missed the 1" isolation and the file name did not indicate an isolated model. I should have deleted the file.

This is also why I probably saw the font/size change with my print outs. That model originally was a simple .50 wave model from way back maybe, back before I got the upgrade and was using the Demo version, and long before I changed the font/size output default to the smaller typeset I currently use.
Here is an example of the typeset difference that concerned me. They are not the same file in question here, because I did not save the file, but it does demonstrate what I was trying to say.

View attachment Example of typeset change.pdf

 

[bob85]

eddie,
its not my idea, its what the smart folk like maxwell tell us about common mode impedance,

a 1/2wave multiple coax outer braid or mast length that is connected to ground gives us a low impedance/ high cm currents ( ji's worst case scenario )
a 1/2wave isolated from ground gives a high impedance/low cm currents,

odd 1/4wave multiple mast length does the opposite with regards to been grounded or not grounded, in the same way as 1/2wave electrical of coax reflects its terminating impedance and odd 1/4waves invert the impedance,

the fact many people use no radial end-feds without isolation and don't seem to have issues tells me w8ji is right in saying we won't always have a problem, some people are lucky,

i noticed you had more segments in the 1/2wave multiple mast model, you also had no segments in the radials, i never noticed the font size

 

[Marconi]

eddie,
its not my idea, its what the smart folk like maxwell tell us about common mode impedance,

a 1/2wave multiple coax outer braid or mast length that is connected to ground gives us a low impedance/ high cm currents ( ji's worst case scenario )
a 1/2wave isolated from ground gives a high impedance/low cm currents,

odd 1/4wave multiple mast length does the opposite with regards to been grounded or not grounded, in the same way as 1/2wave electrical of coax reflects its terminating impedance and odd 1/4waves invert the impedance,

the fact many people use no radial end-feds without isolation and don't seem to have issues tells me w8ji is right in saying we won't always have a problem, some people are lucky,

i noticed you had more segments in the 1/2wave multiple mast model, you also had no segments in the radials, i never noticed the font size

I understand that Bob, but it was easier to explain to the reader that you brought the idea up, and that is all I meant. However, you're clarifying this fact probably helps some readers understand better.

Bob, not that I agree with exactly everything you say, but you have presented plenty of references here on WWDX that would never have been presented, and maybe this is one of those cases. I always consider to give credit for sources I use. I think it is good business.

Well this morning I have attempted to start over from the beginning. Believe me doing all the iterations that I thought necessary...gets pretty confusing and errors are sure to crop up.

I made errors, because I can't not, at this time, duplicate what I thought I saw the other day. If I was just dealing with my old procedure where I used the mast, attached or not, to demonstrate the effect of currents...then this would be easy. However, when I started adding my idea for how the feed line feature should work or be applied...I opened up a new can of worms if seems.

To me, this suggest that my idea for using the Eznec FL feature is likely in error in some regard, and I don't understand it at this point. The data I enter with the mast is attached looks fine, the results seem at least predictable and duplicable. But, when I isolate the mast, which I know is an issue that is sure to come up, things are not so predictable...and I think results are seldom good.

So far today, this is what happens...even when the the antenna is simple like a 1/2 center fed dipole or the Starduster. Both of these antennas, like most, have some currents on the mast to be sure, but these two are probably as minimal as we will see without a device to fix the problem.

So, I guess my idea here was wrong...whatever I was trying to demonstrate in the beginning. Right now I can't even remember exactly what that was, and I don't care right now to try and go back to check out what it was in this thread.

Sorry, but there are just too many side issues for me to track with modeling on my mind. I thought I had it, but it was wrong.

Bob, thanks though, for bringing this to my attention. I don't give a hoot about always being right on everything, I think the truth is more important, even when I have to go sit in the corner.

 

[Marconi]

eddie,
its not my idea, its what the smart folk like maxwell tell us about common mode impedance,

a 1/2wave multiple coax outer braid or mast length that is connected to ground gives us a low impedance/ high cm currents ( ji's worst case scenario )
a 1/2wave isolated from ground gives a high impedance/low cm currents,

odd 1/4wave multiple mast length does the opposite with regards to been grounded or not grounded, in the same way as 1/2wave electrical of coax reflects its terminating impedance and odd 1/4waves invert the impedance,

the fact many people use no radial end-feds without isolation and don't seem to have issues tells me w8ji is right in saying we won't always have a problem, some people are lucky,

i noticed you had more segments in the 1/2wave multiple mast model, you also had no segments in the radials, i never noticed the font size

Bob, it is not possible to have no segments. 1 segment will shows up maybe looking like no segment. If you are talking about an image with the short 12"-18" radials...then I think I might have assigned 1 segment there.

The only reason I used few segments on these particular models was, because I was possibly going to post them, and this way it still shows what is going on with the currents nicely without a really long report.

Since I was changing the length of the radiators from 1/4 to 1/2 wavelength, that too require a change in segments. I caught myself forgetting that from time to time...trying my best to keep all my thinking and actions on par.

I try to keep the segment lengths as short as possible in other cases, but here I just tried to keep all the wire segments as close to the same length as possible, and I may have failed doing that too.

These are pretty simple models, but keeping up with all the changes and the iterations in the process gets complicated.

Yep, some folks do get lucky, but I'm a optimist, and that tells me there is a possible solution to my problem that does not require me to figure out the error of my ways. In that case you will note that W8JI never divulges what that lucky way might be, but he is fast to call attention to a worst case scenario.

That also suggest to me there are good scenarios to be had. You will also find where he discusses that he can create a near perfect 1/4 wave antenna, and he shows us a picture of what that pattern looks like, but I could not find any explanation for what he did to accomplish that. There are some words there, and I tried what I thought he said, but it did not work using Eznec as I recall or else maybe I just misunderstood.

I wish I had all the answers and could demonstrate and explain them too.

 

[CowboyCody]

I wish I had all the answers and could demonstrate and explain them too.

If you could do that you would be set for life

 

[Marconi]

If you could do that you would be set for life

Yep Cody, that's got to be a dream.

 

[bob85]

eddie,
i was talking about the radials in the 1/2wave multiple model titled Bob's follow up.pdf you used one wire with no segmentation rather than the 3 segments per radial in the other model, i have no idea how or if that effects the model its just something i noted as been different,

i don't think you need bother with the coax to show the effects of different common mode impedance so long as you include the mast,
in the real world its near impossible to guesstimate the electrical length over the coax braid and through your station equipment to ground unless the coax is touching the ground or connected to a ground rod,

i think you will find that worst case = 1/2wave multiples connected to ground or odd 1/4waves not connected to ground,

a best case scenario would be 1/2wave multiples not connected to ground or odd 1/4wave multiples connected to ground,

w8ji shows us how to minimise cm currents for a starduster which i see as dipole like 1/2wave would be to isolate the mast and add a choke or some other form of line isolator just below the radial tips,
Ground Plane Verticals

you often see people add or advise people to add willy nilly a ground wire from their antenna to a ground rod,
that may or may not provide a degree of safety but it can also be a disaster with regards to common mode currents and antenna pattern which they never take into account, it can also be a danger and against wiring code,

i 100% agree you should post links, you should HAVE to post links or tell folk where to look for info,
it is much more useful than making your own dogmatic physics up AMPOWER style,
im always looking to learn something new EVERY DAY,
if i get something wrong that's just something new i learned

 

[Marconi]

eddie,
i was talking about the radials in the 1/2wave multiple model titled Bob's follow up.pdf you used one wire with no segmentation rather than the 3 segments per radial in the other model, i have no idea how or if that effects the model its just something i noted as been different,

Bob, I believe you're talking about the model #2, here. In that case I used a bad angle, and it does look like it only has one radial at the base, and the segment marks are hard to see. Model #2, was at 36' feet. Model #1, was at 48' feet. Otherwise the models were exactly the same except for the heights and the angle I used to produce the Antenna View image.

Also remember that I was working with models at 48' feet and you asked to compare a model with a 1/2 wave or multiple at 36' feet, so I started with the model that I did not save. So, I believe the model #2, is also in error. I can't duplicate it without a true copy of model #1.

I could be wrong here, but I hope I was clear and explained this according to your understanding.

i don't think you need bother with the coax to show the effects of different common mode impedance so long as you include the mast, in the real world its near impossible to guesstimate the electrical length over the coax braid and through your station equipment to ground unless the coax is touching the ground or connected to a ground rod,

I agree completely.

The only reason I decided to use the feed line feature was because of the good results I first saw, and thinking I had done a good job, done it right, and the results were correct. All to find out, in not being able to answer your subsequent question...that I was probably dead wrong. So these two models should be ignored.

i think you will find that worst case = 1/2wave multiples connected to ground or odd 1/4waves not connected to ground,

a best case scenario would be 1/2wave multiples not connected to ground or odd 1/4wave multiples connected to ground,

I agree here too.

w8ji shows us how to minimise cm currents for a starduster which i see as dipole like 1/2wave would be to isolate the mast and add a choke or some other form of line isolator just below the radial tips,

Ground Plane Verticals

I'm probably wrong, but I recall W8JI said something to the effect that he isolated the radials, and I thought he was meaning that literally. When I tried to model that idea, it failed. I'll read it again.

you often see people add or advise people to add willy nilly a ground wire from their antenna to a ground rod,
that may or may not provide a degree of safety but it can also be a disaster with regards to common mode currents and antenna pattern which they never take into account, it can also be a danger and against wiring code,

I never understood such an idea.

i 100% agree you should post links, you should HAVE to post links or tell folk where to look for info,
it is much more useful than making your own dogmatic physics up AMPOWER style,
im always looking to learn something new EVERY DAY,
if i get something wrong that's just something new i learned

I agree here too, and really appreciate folks that quote the last two.