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

[mackmobile43]

Maybe they were thinking lots of guys would be running these antennas at lower heights being the reason for 8 shorter radials.

I can't imagine trenching in 100, 80 meter radials.

 

[Shockwave]

Even at lower heights, full 1/4 wave radials produce more gain then shorter ones. The difference is really quite small and you would have a difficult job determining any difference between a Maco V58 and the Sirio S-827. I think Sirio just decided to go with smaller diameter less expensive tubing and since they cut them in half, why not just add 4 more? You have to admit those 8 radials look cool and take your mind right off the fact they are short. Nice job on your Vector 4000 too Mack, and it will reach further then any of the antennas being discussed in this tread.

 

[Shockwave]

Or if you live in a very high wind area where a fiberglass antenna will flex better than an aluminum antenna, yes?

Fiberglass certainly does flex better then aluminum. I can't remember the last aluminum fishing pole I've seen. The one weak link with the fiberglass antennas are the metal couplers pressed or epoxied onto the fiberglass ends. I know of many people who have found the top part of their Antron 99 in their back yard when mowing the lawn. On the brighter side I've seen that the Imax 2000 has better mechanical joints. If you want an antenna that can really handle the extremes Mother Nature can throw at it, about the best choice would be the Interceptor 10K.

 

[mackmobile43]

Even at lower heights, full 1/4 wave radials produce more gain then shorter ones. The difference is really quite small and you would have a difficult job determining any difference between a Maco V58 and the Sirio S-827. I think Sirio just decided to go with smaller diameter less expensive tubing and since they cut them in half, why not just add 4 more? You have to admit those 8 radials look cool and take your mind right off the fact they are short. Nice job on your Vector 4000 too Mack, and it will reach further then any of the antennas being discussed in this tread.

Thanks, looking forward to doing more testing and yes that does make the antenna sexier with more radials.

Thanks for the timely answers.

 

[BOOTY MONSTER]

Even at lower heights, full 1/4 wave radials produce more gain then shorter ones. The difference is really quite small and you would have a difficult job determining any difference between a Maco V58 and the Sirio S-827. I think Sirio just decided to go with smaller diameter less expensive tubing and since they cut them in half, why not just add 4 more? You have to admit those 8 radials look cool and take your mind right off the fact they are short. Nice job on your Vector 4000 too Mack, and it will reach further then any of the antennas being discussed in this tread.

" full 1/4 wave radials produce more gain then shorter ones."


how about using longer elements ? 12 footers or 1/2 WL 18 footers .....
when using 4 (or more) of them is there any noticeable gain from them being longer ? would the 12 footers have any negative effects since they wouldnt be a even 1/4 WL or a multiple of it ?

 

[Shockwave]

" full 1/4 wave radials produce more gain then shorter ones."


how about using longer elements ? 12 footers or 1/2 WL 18 footers .....
when using 4 (or more) of them is there any noticeable gain from them being longer ? would the 12 footers have any negative effects since they wouldnt be a even 1/4 WL or a multiple of it ?

To the best of my knowledge I've never heard of any advantage when going beyond 1/4 wave radial length. There is some talk that the radials should be 5% longer then the calculated 1/4 wave for best performance. Even that 5% doesn't seem to make too much difference. Can you use longer then 1/4 wave radials? Yes. Consider a 2 meter 5/8 wave magnet mount antenna. The 1/4 wave radials would be about 18 inches yet we place them on a car that has a much larger ground plane and they work fine.

 

[Henry HPSD]

Hi All,


Would this info be usefull ?

For a quater wave vertical "sitting" on the ground :
The 0dB reference is 4,1dBI for all.

4 radials 1/4wl long toa 24 degrees 0,96dBI
60 radials 1/4 wl long take off angle 23 degrees 2,6dBI
120 radials 1/2 wl long take off angle 28 degrees 2,8dBI
240 radials 1/4 wl long take off angle 28 degrees 3,0dBI
4 radials 2wl long take off anlge 24 degrees 0,98 dBI
60 radials 2wl long take off anlge 22 degrees 2,9dBI
120 radials 2wl long take off angle 20 degrees 3,6dBI
240 radials 2wl long, take off angle 17 degrees 4,1dBI

If you have a quater wave vertial over very poor ground changing the number from say 25 to 100 radials wont do much on the pattern.
If you go from 30 to 120 radials there is a improvement of 1dB
If you go from 5 to 120 radials there is a improvement of 3 dB.
Over good ground the improvement is sligthly less.

If you have <30 radials over very bad ground (city etc..) it has no use to lengthen them upto 2 wavelengths.
However with more radials it does become worthwill to extend the length to 2 wavelengths.

Where only a few radials are used < 10 the thickness of the radials becomes important.
With the thicker ones on the winning side.
When many are used it is less important as current is devided over all.

The impedance drops as the number of radials increases
approximently 50 ohms with 16 radials and 35 ohms with 120 radials.

POWER loss:
16 radials 0,1 wl long = 3dB
24 radials 0,125wl long = 2 dB
36 radials 0,15wl long = 1,5dB
60 radials 0,2wl long = 1 dB
90 radials 0,25wl long = 0,5 dB
120 radials 0,4wl long = almost 0 dB.


Now we almost never have the antenna sitting on the ground but often 30 feet or more in the air... By lifting the antenna the ground influence become less.
Attached you can find a few eznec plots giving the difference between a 1/4 wave length vertical with 3 or 60 1/4 wl radials at 0 or 30 feet.

Please dont take the given dB's as a fact...it is highly dependable on ground influence.
However the differnce between the number of radials is what you will get.

So overall.....

The more the better..
Only with a very large amount of radials it is usefull to extend them to 2 wavelengths.
If you can construct 60 radials 0,2wl you have about max reached..The only "noticable" improvment wich can ge made is lowering your tao with 5 degrees by using 240 radials 2wl long.

The best would to place the vertical over sea as that would be the perfect ground.
That is the reason why maritime mobile stations are always lound with only a small vertical.

Reference:
arrl antennabook
lowband DXing
rothammel
HF antenas for all location

Hope it helped.

73 Henry
19SD348

 

[Shockwave]

Hi All,


Would this info be usefull ?

For a quater wave vertical "sitting" on the ground :
The 0dB reference is 4,1dBI for all.

4 radials 1/4wl long toa 24 degrees 0,96dBI
60 radials 1/4 wl long take off angle 23 degrees 2,6dBI
120 radials 1/2 wl long take off angle 28 degrees 2,8dBI
240 radials 1/4 wl long take off angle 28 degrees 3,0dBI
4 radials 2wl long take off anlge 24 degrees 0,98 dBI
60 radials 2wl long take off anlge 22 degrees 2,9dBI
120 radials 2wl long take off angle 20 degrees 3,6dBI
240 radials 2wl long, take off angle 17 degrees 4,1dBI

If you have a quater wave vertial over very poor ground changing the number from say 25 to 100 radials wont do much on the pattern.
If you go from 30 to 120 radials there is a improvement of 1dB
If you go from 5 to 120 radials there is a improvement of 3 dB.
Over good ground the improvement is sligthly less.

If you have <30 radials over very bad ground (city etc..) it has no use to lengthen them upto 2 wavelengths.
However with more radials it does become worthwill to extend the length to 2 wavelengths.

Where only a few radials are used < 10 the thickness of the radials becomes important.
With the thicker ones on the winning side.
When many are used it is less important as current is devided over all.

The impedance drops as the number of radials increases
approximently 50 ohms with 16 radials and 35 ohms with 120 radials.

POWER loss:
16 radials 0,1 wl long = 3dB
24 radials 0,125wl long = 2 dB
36 radials 0,15wl long = 1,5dB
60 radials 0,2wl long = 1 dB
90 radials 0,25wl long = 0,5 dB
120 radials 0,4wl long = almost 0 dB.


Now we almost never have the antenna sitting on the ground but often 30 feet or more in the air... By lifting the antenna the ground influence become less.
Attached you can find a few eznec plots giving the difference between a 1/4 wave length vertical with 3 or 60 1/4 wl radials at 0 or 30 feet.

Please dont take the given dB's as a fact...it is highly dependable on ground influence.
However the differnce between the number of radials is what you will get.

So overall.....

The more the better..
Only with a very large amount of radials it is usefull to extend them to 2 wavelengths.
If you can construct 60 radials 0,2wl you have about max reached..The only "noticable" improvment wich can ge made is lowering your tao with 5 degrees by using 240 radials 2wl long.

The best would to place the vertical over sea as that would be the perfect ground.
That is the reason why maritime mobile stations are always lound with only a small vertical.

Reference:
arrl antennabook
lowband DXing
rothammel
HF antenas for all location

Hope it helped.

73 Henry
19SD348

This reference is for low band DXing. This is geared towards 160 through 80 meters and does not apply at all to the 27 MHz band.

 

[Henry HPSD]

Sorry shockwave... but no what you are saying isnt rigth.

For antennas it doesnt mather on wich frequency you apply the rules.
as long it is equal in reference to wavelength.

so a have wave length dipole at 1 wavelength heigth on 3,8 Mhz will show the same results as a have wave length dipole at 1 wavelength heigth on 27 mhz etc..

Allmost all antenna rules can be aplied to any frequency

PS...have you ever heard of a standard dipole producing different gain at different frequencies?..

Just buy one of the books and it will be explained...

The behaviour of propagation is different with frequency perhaps thats where you went wrong?

Kind regards,
Henry
19SD348

 

[Shockwave]

Sorry shockwave... but no what you are saying isnt rigth.

For antennas it doesnt mather on wich frequency you apply the rules.
as long it is equal in reference to wavelength.

so a have wave length dipole at 1 wavelength heigth on 3,8 Mhz will show the same results as a have wave length dipole at 1 wavelength heigth on 27 mhz etc..

Allmost all antenna rules can be aplied to any frequency

PS...have you ever heard of a standard dipole producing different gain at different frequencies?..

Just buy one of the books and it will be explained...

The behaviour of propagation is different with frequency perhaps thats where you went wrong?

Kind regards,
Henry
19SD348

When you talk about a vertical antenna and what the ground plane requirements of that antenna are, frequency is one of the most important differences between 160 meter low band DXing and 27 MHz. What you say about the dipole and it's height in terms of wavelength above ground is correct. What you are missing is that the article speaks about ground mounted low frequency vertical antennas very similar to AM broadcast stations that use that many radials to increase the radiation efficiency. With an elevated groundplane on 27 MHz the groundplane requirements are much less then around 1.8 MHz. Adding more then 4 radials will not make a noticeable difference on CB. Look into this further and you'll see the information I've provided is accurate.

 

[bob85]

TIP OF THE WEEK,
adding more than 4 full size radials to an antenna elevated high above ground relative to wavelength is similar to adding chrome spinners to your wheels,

folding them up to where they add constructively to the vertical pattern in a favourable way is like buying better tyres and negates the need for an extensive radial system when the antenna is not mounted high above ground,

the downside is only people that understand tyres appreciate what you did

 

[Henry HPSD]

Hi Shockwave,

Thanks for the fast replay !

...But That is exactly what i am saying....how can you disagree with me ?

In my first answer:

1) I started off by saying it concernes quater wave verticals sitting on the ground.
2) In the attachement you can see the difference on 27mhz.
calculated by Eznec. With different heigths , so with the elevetad radials...
I also mention the difference is less when the antenna is higher in the air.

Now when a groundplane is placed at the ground the radials have the largest influence..
So that is why i would prefer to mention the differece when the antenna is placed at
0 feet. IF they are elevetad difference would be less significant..(as earlier mentioned)

I dont understand why you quote my entire reply and then just say...does not apply at all...
I disagree.... wouldnt the difference between 60 and 120 radials at 3,5 or 27mhz be nearly the same?

To my believe i have given the maximum difference. If you think otherwise please give me some facts.

About your remark about the 4 radials. I am not saying there will be a big improvement.
(not looking at t.o.a. because of differnet heigth)
we are talking about less the 3dB... (when the antenna is at the ground) at heigth as mentioned this is less... so again...why are you saying i am wrong?
Wasnt 6dB 1 s-unit and 2..3 dB of difference in gain is about the first the human ear could notice..


Kind regards,
Henry

 

[BOOTY MONSTER]

hello henry , welcome to the forum .

im just a cber , not a ham but ive become fascinated about antennas . i understand that having the feed point of a verticle antenna at ground level requires many many many ground elements . i think most of us cb'ers have our antennas feed point about 1/2 a WL (18 feet) or more above the ground . i understand higher is better , but usually money or location keeps a good deal of us from going higher . its seems the main thing is to get the feed point above any nearby structures roofs and we can usually do fairly well . in the cb antenna section were pretty much always talking about elevated base antennas or mobile antennas .

anyhow , what are your thoughts on ground elements on elevated antennas with the feed point 20 or 30 or 40 feet above the ground , on 27 MHz. ?

 

[Shockwave]

Hi Shockwave,

Thanks for the fast replay !

...But That is exactly what i am saying....how can you disagree with me ?

In my first answer:

1) I started off by saying it concernes quater wave verticals sitting on the ground.
2) In the attachement you can see the difference on 27mhz.
calculated by Eznec. With different heigths , so with the elevetad radials...
I also mention the difference is less when the antenna is higher in the air.

Now when a groundplane is placed at the ground the radials have the largest influence..
So that is why i would prefer to mention the differece when the antenna is placed at
0 feet. IF they are elevetad difference would be less significant..(as earlier mentioned)

I dont understand why you quote my entire reply and then just say...does not apply at all...
I disagree.... wouldnt the difference between 60 and 120 radials at 3,5 or 27mhz be nearly the same?

To my believe i have given the maximum difference. If you think otherwise please give me some facts.

About your remark about the 4 radials. I am not saying there will be a big improvement.
(not looking at t.o.a. because of differnet heigth)
we are talking about less the 3dB... (when the antenna is at the ground) at heigth as mentioned this is less... so again...why are you saying i am wrong?
Wasnt 6dB 1 s-unit and 2..3 dB of difference in gain is about the first the human ear could notice..


Kind regards,
Henry

I'm sorry I missed where you said the 27 MHz antenna was mounted at ground level. While this is common practice on the lower HF bands, there are not too many applications where you would do this with a CB base antenna. The signal gained with height on CB is way more then gained with a full buried radial system on the ground.

I also find it interesting that EZNEC says a ground mounted 27 MHz 1/4 wave could have an improvement measured in db's rather then tenths of a db by going over 4 radials. If someone else has more experience with a ground mounted CB 1/4 wave and it's radial system, please share your input. I'm interested in learning something new especially if my initial understanding was wrong.

 

[mackmobile43]

TIP OF THE WEEK,
adding more than 4 full size radials to an antenna elevated high above ground relative to wavelength is similar to adding chrome spinners to your wheels,

folding them up to where they add constructively to the vertical pattern in a favourable way is like buying better tyres and negates the need for an extensive radial system when the antenna is not mounted high above ground,


Will these help me bob85?:tongue: