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To Ground Plane, or not to Ground Plane? That is the question...

Like most things in electronics you reach a point of diminishing returns for effort/expense put in,and radials/counterpoise are no different.

sometimes you just have to be happy with what ya got,and make the best out of it.

as for adding radials to the point where you have a 120 or more,then surely you reach the point where you have one solid plate as a radial/counterpoise,now is that one big radial,or 360 joined ones? i'm sure that could be argued till the cows come home.

by the time you get too adding 120 radials,the expense and lack of improvement would dictate your money/effort/time would be much better invested in a beam or a quad antenna,as you would gain far more.too many people seem hung up on finding the perfect vertical monopole antenna (seems to be the holy grail of cb'ers),but the reality is there are far more efficient antennas of other designs out there to waste time trying to squeeze every drop of performance out of one type of antenna.
 
The Ringo looks like the 5/8 wave but it worked without radials because it is an end fed half wave. This is the same reason the old Shakespeare Big Stick, and Antron 99 perform with no radial system. The Imax 2000 is entirely different and probably why it took many more years to develop this 5/8 wave design.

The mast or coax will not act as an effective ground plane or radial system for the 5/8 wave. This is not a difference of opinion, it's an easily proven fact. Use any coax and mast on a Maco V58 and try getting the antenna to work without radials. The impedance will be way to high to match the 50 ohm feedline and it will drop at least 6db in signal.

There are things you can do in a compromised antenna like the Imax to match it without radials. It won't work as good as the antenna that did not have a compromised matching network like the V58. The coax and mast cannot simulate a 90 degree ground plane required to match the 5/8 wave to 50 ohms. The matching network with that series capacitor is compensating for the impedance mismatch.

I design and construct antennas for commercial broadcasting. The goal here is maximum coverage and that leaves little room for compromised antennas. What can be used for counterpoise on a 1/4 wave will provide a completely undesirable high angle radiation pattern on the 3/4 wave.

If you think the first few radials makes a difference on the Imax, by all means add them. I know it will take a digital field strength receiver to split that hair. If you want a 5/8 wave with radials, buy the one designed to work with them. Not the one designed to work without them.
 
Hello All !

@Marconi
About the effectivness expected by military or commercial use...
I totally agree those are my thougths. If it was 100% effective they would use it.
Could one say...the imax isnt the best there is, without radials ?

About the impedance changes of >1/4 wave verticals and heigth.
You pointed out a new thing for me ! so thanks for that.
Ill be testing it on the gear here this afternoon..

@Shockwave:
We are speaking about the same.
You can say the imax has a different impedance matching unit than any other.
This is logical, cause without radials you need to match other values..
As i see it, it is not that the matching unit compensate the l"ack" of radials it is the matching unit matches the impedance wich is present due to the "lack" of radials.

It is only logical that a 5/8wave without radials would have a significant more loss cause the matching unit is planned to work with radials so there will be more loss..

You design antennas, could you plot the difference between the imax with or without radials? I guess dB figures would be the same as given earlier for a 5/8wave..
And i agree the difference is very small.. with the first radials attached and will become less when after that you add more.

About my remark about the radials for a 1/4 or 3/4 wave. Perphaps i wasnt clear enough in my previous post. I wasnt try to say they will produce equal results.
I was trying to point out a 1/4 wave or 3/4 wave depend more or less on radials.
You are saying :
"What can be used for counterpoise on a 1/4 wave will provide a completely undesirable high angle radiation pattern on the 3/4 wave."
Wouldnt the length of the radiator provide that high anlge when used a counterpoise for a 1/4 wave on a 3/4 wave ? and not the radials as a main thing ?

Anyway thanks for your input it is highly appriciated !

Enjoy the (rest) of the weekend,
H.
 
Since it is the removal of the radials that causes the drastic impedance change, it is logical to say the matching network has been designed to compensate for this. Rather then plot the difference between an Imax with or without radials, it would be more revealing to you if you measured the difference between an Imax with radials and the Maco V58. The antenna designed to use radials will have more gain.

With respect to the 3/4 wave, in this case the radiator length has much less effect on the radiation angle then the antennas radials do. The radials on the 3/4 wave have a profound effect on radiation angle. Fold them down like a 1/4 wave and you'll have the maximum radiation above 45 degrees. Fold them upwards and you can lower the radiation angle near the horizon.
 
Hi shockwave,

I understand your point of view about the first section of your replay. And agreed it is how you explain it, i would explain it otherwise but were both saying the same.

About the 3/4 wave.. oke, guess on the forum the vector 4000 is beeing discussed so ill read that first.. It would be very intresting if one could lower the radiation angles as for now, i always thougth beyond 5/8 wave there would be to much "lobs" so overall efficiency would drop, if i read you rigth you could bypass that ? In the comming couple of weeks ill look into verticals more as normally i am a bit more on active in beams..

A bit off topic, but perhaps we could discuss collinears in the near future.
As i recon a "phased" vertical between 30..40 feet could make a noticable difference ..
(building now one base is 50mm ...2,5 inch)

Do you use eznec ? i can send you a couple of files. Wich i am building.

See u all around :-)

73. H.
 
As some one said, if it isn't included in the box then it wasn't designed to use it and if it was designed to use it and they want to charge extra for it then you need to follow your conscience and say "hey the other guy included gp radials with his antenna so it must require them".

And furthermore why can't anyone get in contact with the designer of this antenna and ask exactly why and how it works with or without gp radials?
 
Your line of thinking with the conventional 3/4 wave groundplane is correct. The radiation pattern will have several lobes at relatively high angles. The main lobe would be about 45 degrees above the horizon. They are basically only useful for satellite work.

Check out the Vector that was modeled after the Sigma IV. Folding the radials upwards on a 3/4 wave not only effects the impedance of this antenna, it also pulls the main lobe back down on the horizon.

Sirio manufactures a FM broadcast version of this antenna for my company and I've tried my best to model the antenna using EZNEC with little luck. I've even had people who are familiar with the program do this and they come up with a near 45 degree main lobe. It works for many antennas but not the one I work with.

I've experimented with collinears also. The 3/4 wave over 3/4 wave does not seem to add the same 3db that dual 5/8 wave sections would. I think that has to do with the top section having high angle lobes without that cone radial system. The 5/8 wave over a 1/4 wave also works well.
 
I put insulators in my top guy wires and used dacron for all the rest. my top guy wires are 23 foot long to the insulator and come off the top u-bolt and now my imax hits 2 pounds more everywhere, specially long range. static dropped and ears came up to. my buddy a mile away and me both run 2995s, he has an enforcer and he used to get me everywhere we talked but now i get him a lot of places.
i threw away that radial kit. had a couple guys want to buy it but i wont sell somthing that dont work, not even to an enemy
 
Needle Bender said:
I put insulators in my top guy wires and used dacron for all the rest. my top guy wires are 23 foot long to the insulator and come off the top u-bolt and now my imax hits 2 pounds more everywhere, specially long range. static dropped and ears came up to. my buddy a mile away and me both run 2995s, he has an enforcer and he used to get me everywhere we talked but now i get him a lot of places.
i threw away that radial kit. had a couple guys want to buy it but i wont sell somthing that dont work, not even to an enemy
Click to expand...

Two "S" units is 12db! Something else had to be effecting that measurement because gaining 12db from adding those radials is not possible. While it's more effective then the ground plane kit, it would take installing the antenna over an ocean of salt water to approach a 12db increase. If you did that with the radials or coax in the water, you would see incredible gains.

Trying to simulate this type of ground plane with an elevated antenna using wire radials would struggle to add even a single db of gain. Don't get me wrong, I'm not saying you've been untruthful. I'm suggesting if you saw two "S" units gain then things like S meter inaccuracy and possible distortion of the omni directional pattern from the guy wires were more likely responsible.

Being that the guy wires are that close to the feedpoint, it is possible they are effecting the radiation pattern in ways that are not so obvious. They are likely to form more intense lobes in the directions off the ends of the 23 foot guys wires with nulls in between. Meaning that your signal went up in some directions but at the expense of others.
 
With respect to the 3/4 wave, in this case the radiator length has much less effect on the radiation angle then the antennas radials do. The radials on the 3/4 wave have a profound effect on radiation angle. Fold them down like a 1/4 wave and you'll have the maximum radiation above 45 degrees.
Click to expand...

The radiation pattern will have several lobes at relatively high angles. The main lobe would be about 45 degrees above the horizon. They are basically only useful for satellite work.
Click to expand...

Would this also hold true of a 5/8 wave ground plane?


73
Jeff
 
Shockwave said:
Two "S" units is 12db! Something else had to be effecting that measurement because gaining 12db from adding those radials is not possible. While it's more effective then the ground plane kit, it would take installing the antenna over an ocean of salt water to approach a 12db increase. If you did that with the radials or coax in the water, you would see incredible gains.

Trying to simulate this type of ground plane with an elevated antenna using wire radials would struggle to add even a single db of gain. Don't get me wrong, I'm not saying you've been untruthful. I'm suggesting if you saw two "S" units gain then things like S meter inaccuracy and possible distortion of the omni directional pattern from the guy wires were more likely responsible.

Being that the guy wires are that close to the feedpoint, it is possible they are effecting the radiation pattern in ways that are not so obvious. They are likely to form more intense lobes in the directions off the ends of the 23 foot guys wires with nulls in between. Meaning that your signal went up in some directions but at the expense of others.
Click to expand...

i aint no gennius, just did what a hammer told me and it worked. hell it could be 12 thousand dbs for all i know, and i dont know bout no meter innacurasy i just saw what i saw and know what people tell me. old man walter with his five hundered dollar antnena gets almost mad at me now when i hit somone harder than he does. he used to stomp me purdy hard in most directions but now that i got them 5-9 radials like the hammer called em i get out just fine and old walter, well hes startin to wonder why he done spent five hundered dollars when he coulda spent one hundered and did just fine.
seems to be workin bout the same now in all directions. i know i can get walt in at least three directions to more locations then just one now with them 5-9 radials.
 
Shockwave said:
Two "S" units is 12db! Something else had to be effecting that measurement because gaining 12db from adding those radials is not possible. While it's more effective then the ground plane kit, it would take installing the antenna over an ocean of salt water to approach a 12db increase. If you did that with the radials or coax in the water, you would see incredible gains.

Trying to simulate this type of ground plane with an elevated antenna using wire radials would struggle to add even a single db of gain. Don't get me wrong, I'm not saying you've been untruthful. I'm suggesting if you saw two "S" units gain then things like S meter inaccuracy and possible distortion of the omni directional pattern from the guy wires were more likely responsible.

Being that the guy wires are that close to the feedpoint, it is possible they are effecting the radiation pattern in ways that are not so obvious. They are likely to form more intense lobes in the directions off the ends of the 23 foot guys wires with nulls in between. Meaning that your signal went up in some directions but at the expense of others.
Click to expand...

Shockwave, I don't have a clue what is really going on with NB's setup, but in your post #53, last paragraph, you talk about a collinear 5/8 wave, albeit the 3db advantage you suggest is not near the 2 Sunits that Needle Bender has experienced. Maybe that is what is going on over at his location---among other things to make the improvement he sees.

It may be coincidence, but NM5K, look him up on the Internet, here in Houston builds a 5 radial GP kit for his 5/8 radiator and he claims similar and remarkable collinear free space gains of 5.1 dbi, at least according to modeling. I have posted all of his 10 meter 1/4, 1/2, and 5/8 wave work in my picture album here on WWRF if you want to take a look at what he says.

Personally, I am dubious about such gains too, but here is a claim that supports close to what NB says.

NB, talks about different insulators and maybe I don't understand the distinction, but maybe he as actually created a collinear gap between these two 5/8 wave elements. Typically this will require some kind of coil to connect the two elements, but none was mentioned. But again, if the Sigma IV/Vector 4000/your stuff makes a collinear shift in phase without this gap, then why not in this case.

NB, can you post some pictures? I can tell you if your's looks like NM5K's. His setup is very slanted to the ground and is less than 30 degrees.

BTW NB, what do you mean when you post 5-9 radials?
 
Just for grins...

That 5 dBi gain mentioned is 'free-space' gain. that translates to about 3 dBd gain, if the antenna is mounted in such a way as to minimize -all- detrimental effects (environment, height above ground, etc.). All that translates to maybe 1/2 of an 'S' unit, if that 'S' meter is properly calibrated (which almost none are). Just going by tose numbers, it is reasonable to expect to see that sort of 'improvement' when comparing a 5/8 w antenna with a 1/4 w antenna. Doing the same comparison with a 1/2 w antenna will show a much smaller difference, something on the order of maybe 1.5 dBd difference, which isn't typically noticeable.
It's just a fact that any antenna can be optimized. There are several ways of doing that, it just depends on which route you want to go with which antenna. Thinking that a particular style/shape/length/number of radials making up a 'groundplane' (or the 'other half' of the antenna) is the ultimate answer just isn't gonna hold much water. I guess it'd be enough if you were dying of dehydration, but it ain't gonna fill a good sized puddle. ;)
- 'Doc
 

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