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Extended Double Zepp?

B

blue runner

Member
Jul 8, 2012
22
0
11
Anyone thought about adding 3 or 4 diagonal radials (like on a CB starduster) 22' 9.5" long to a 5/8 wave CB antenna.

Seems like you would end up with a vertical extended double zepp antenna. It would look like a giant sized StarDuster.

I have been trying to figure out how to make a self supporting vertical EDZ other than with just the typical wire stretched out and the coax at a 90 deg angle.

Appreciate any suggestions or comments.
 

Actually an EDZ is not feed with coax...it's feed with ladder line...(450/300 ohm) and requires a matching network
to get a 50 ohm antenna where coax can be used you would have to extend to 3/4 wave elements...
All the Best
Gary
 
The 5/8 vertical is half of a EDZ in length. It uses a different matching network instead of the twin lead and a 4:1 matching balun that is typicaly used to match a wire EDZ to coax.

I expect to have to do some tuning or matching if I add a 5/8 skirt of radials, but maybe not.

I suspect the metal mast or the surface of the coax shield (like a RFD, resonant feed line antenna) might be making up the "other half" of an EDZ with the 5/8 wave vertical anyway. That may account for the common mode currents on the coax surface that are so typical with that type of antenna.

I think that a 5/8 wave skirt of radials may improve the radiation pattern over a random length mast or coax surface currents. But I don't know if it is worth the trouble. I am hoping to hear from somebody who may have had some experience with it.

Thanks for your observations.
 
I made one of these EDZ using very close measurements to what is on this site using their calculator:

EDZ Calculator

Ironically, I managed a match without the 4:1 balun. I simply used a roughly 53" x 3" spacing ladder line (home made) between the wire dipole (EDZ) and the coax.
With the MFJ-259b I saw 1.0:1 R50 X0 at 27.295 and a 2.0:1 around 28.300. I read similar SWR through the SWR meter.
I may tune more to get it shifted up some later. I saw this through the 50' RG8U coax feedline. No time to fool with it more at the moment.


It should be worth noting that the wire is only 4' above the ridge of my roof, 21' above the earth.

0073_zpsfe53f0bf.jpg


0076_zpsbbcd3563.jpg
 
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Good to see you back Homer.

Did you think when you started you would need the 4:1 balun for this setup to work right?
 
It's what I had read, so I took it for granted that was the way of it.
What I figured I'd use when I first thought to try an EDZ was the matching network I'd used with the 1/2 wave end fed verticals. The figures I'd read for the impedance at the feedpoint seemed to point to that network as a possibility - 1800 Ohms more or less.

I don't know the proof of it, but it matters little as I decided to make the ladder line instead. It was a matter of sticking the spacers in between the first several inches of my wires. Given time I may try the other matcher. I know little about this antenna, but it seems the consensus is a ladder line is necessary to convert it to usable impedance with the coax, yet . . .
I'll have to put the analyzer right at the end of the ladder line to be sure of where the antenna is, and to determine whether the 4:1 balun should be there or not.


Where it is mounted it's a bit noisy, and very directional - more so than the common dipole.
 
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EDZ vertical

Good to hear from you again Homer.

I see you are still doing way cool antenna stuff.

I'm trying to figure out how to make a vertical EDZ.

I could just go with a wire one mounted on the side of my wooden tower and lead the twin lead & coax away at 90 degrees for 8' (the width of my tower).

Could make one outta aluminum tubing mounted on a boom extended from my tower too, that would allow me to rotate it horizontally or vertically.

What I really want is a self supporting model that can go on the end of a push up pole like the starduster but in the giant economy size.

The top vertical 5/8 wave section is half of my objective, the lower half is what keeps me scratching my head. I wonder if the mast & coax feed line might interfere with the function of the lower 5/8 skirt (doesn't hurt the starduster)?

I figure I can make the ladder line out of maybe two pieces of narrow flat aluminum bar with spacers and bent into a hoop half way around the middle of the antenna. One end bent back toward the mast where coax can be attached and the other end also bent back toward the mast and attached to the upper & lower elements.

Might be more trouble than its worth, but the idea keeps nagging at me from the back of my mind.

Essentially just adding sloping diagonal radials 5/8 wave long to a 5/8 wave vertical would seem to be the same thing.

Been asking around and searching the internet but can't find anything, not even for the higher frequencies where the EDZ size might be more practical.

Apparently a EDZ vertical is never done and there is probably a good reason for it, but I haven't found out why yet.
 
Likely one of the reasons a vertical EDZ isn't done is because folks on 11 meters haven't been homebrewers to the extent that Hams have been, and for all practical purposes wire antennas have been horizontally oriented in the Ham community almost exclusively.

I do imagine the large matching system on the EDZ has made it impractical, too.

I think the self supporting vertical is not a big problem provided the matching network can be reduced in size and mounted in a practical way. As my thoughts have been so far, should the matcher I use with the EFHW be usable it is done.

5/8 wave aluminum tubing straight up from center insulator, 5/8 wave tubing straight down. Coax up through the bottom tube to the center insulator, and the matcher mounted there feeding the two ends. The whole thing would be VERY long, and that alone makes it a doubtful project in terms of value to logistics ratio, but doable.

This match handles the kind of impedance mismatch associated with the EDZ with ease.

match2_zps621e05d8.jpg


As for your idea on the double bars curled around, I have pondered such a thing for other applications than an EDZ. I thought more in terms of a Beta Match at the center of a 5/8 wave dipole similar to the gainmaster replacing the capacitor/stub match inside the GM. If workable it would certainly end the discussion on power handling that has been an enduring subject for that antenna, and simplify homebrewing possibilities for we simple types - if you don't mind ugly.

4e2mYagi.jpg
 
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Thanks for the reply Homer,

I've been speculating about this "Super Starduster" EDZ for some time now.

Ever since I started dying my hair grey to get the senior citizen discounts, I don't look forward to multiple trips up & down my tower anymore. Must be chemicals in that grey hair dye that saps my strength & resolve.

I just find it interesting that I can't find ANY reference to anyone building a vertical EDZ for any band. It would seem that a "real" 3 Dbd gain would be so attractive to try it.

You would think that someone would post even a FAILED attempt. Maybe I will be the first to post about such a failure.

I know that computer modeling can only approximate performance in a real world application but I wonder if the modeling can give any insight. Maybe someone handy with the program will develop enough interest to try to model it. I expect the vertical feed modification and metal mast & coax feedline interaction may be difficult for the software or the guy entering the data.

At this point I think I may build a vertical wire EDZ on my wooden tower (maybe a tubing upper half for height) and & get some readings from locals compared to my starduster. Then maybe a 5/8 wave tubing vertical (get some readings) and then just try some wire 5/8 wave long sloping radial skirts and see if there are any improvements after fiddling with the matching network.

I really need to get offa my butt and make a tilt up mast like you have and save myself a few trips up the tower.
 
There is always the difference that making and trying adds to what we learn.

Another thought about changing an EDZ from horizontal to vertical - as with all dipole antennas the propagation characteristics will likely change when the antenna goes upright. The way the earth treats the pattern of a horizontal antenna compared to a vertical antenna is well documented, and that will probably be your experience when you try it - a difference that may not give you the results you are looking for.
 
Marconi said:
What is the square device on the roof at the end of the ladder line?
Click to expand...
It is a plastic passive attic vent. There is no metal in it at all. There are two of them visible in the other photo.

If that is not what you are referring to, then I take it you want to know what the smaller squarish thing is.
It is merely a plastic plate that I have my PL connector embedded on to keep it secure for connecting the ladder line and a coax to it.
 
HomerBB said:
It is a plastic passive attic vent. There is no metal in it at all. There are two of them visible in the other photo.

If that is not what you are referring to, then I take it you want to know what the smaller squarish thing is.
It is merely a plastic plate that I have my PL connector embedded on to keep it secure for connecting the ladder line and a coax to it.
Click to expand...

I think I was confused as usual with your description. I was thinking that square thing might be the tuning setup you used from your EFHW, and that is how you got the antenna to match perfectly...since you didn't use the 4:1 balun. Isn't that strange that the calculator website indicated that the balun shown was recommended and was necessary to handle the apparent mismatch...and that it ended up not being needed at all? I guess this is just another case about chokes and such that are claimed to be essential for some antenna operations, and doing without the device just doesn't seem to make a difference that is detectable.

Beetle just made a post in another thread about chokes/baluns, and told somebody that he has used various dipoles types for years, and that he never found a need for a choke or balun in his experience. This is about the same story I often relate, as in my experiences using such devices, where I find their use dubious at best.
 
I like to use a choke for CMC control.
A 4:1 balun would indicate that the impedance expected at the shack end of the ladder line should have been in the 200 - 300 ohms range as one source I read said the 4:1 balun should give a useable match to 50 Ohm coax.

The coax choke has been said to have 1:1 balun potential addressing not only CMC as a choke, but offering a smooth transition from the unbalanced coax to the balanced dipole or similar antennas.
My experiences with the coax choke has been noticeable in one consistent respect - I see the SWR read better on the outer edges of the bandwidth. The center stays the same.
Because I have not done an EDZ before I don't know much about what to expect from the feedpoint mismatch. First good opportunity I will put the MFJ analyzer right at the bottom of the ladder line and see what's going on right there for sure.

You are right, though. Often we find our experiences don't hold up to the arguments put forward . . .
 

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