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horizontal vs sloped ground elements on a vertical ?
- Thread starter br549
- Start date
basically any vertical with ground elements . all else being equal , assume using 4 quarter wave length ground elements below the feedpoint on the same vertical , height and location , the only difference being the ground elements being parallel to the ground or sloped down at 35-55 degrees .
i trust field strength meters , but i don't trust every bodies interpenetration of what they're seeing on the meter , reflections , obstructions , ground conductivity , in a valley or on a hill , and more can effect those readings and if not accounted for can skew actual results .
i trust field strength meters , but i don't trust every bodies interpenetration of what they're seeing on the meter , reflections , obstructions , ground conductivity , in a valley or on a hill , and more can effect those readings and if not accounted for can skew actual results .
Running some models myself using 4nec2...
The 0 model is horizontal, the other numbers are that many degrees below horizontal.
These models are mounted 18 feet above the earth. I also tuned all of them to resonance and did it in such a way that the vertical elements were the exact same length as the radial elements in the individual models.
Essentially, when it comes to gain, horizontal radials provides the most low angle (in this case 15 degree radiation angle) gain, and as you angle the radials down, that gain drops. However, you won't notice a difference in gain as the worst angle has -0.29 dB less gain from the model with horizontal radials. The more I angled the radials down the less gain the model had.
It should be noted that the exact opposite is happening with the higher angle lobe (up at the 45 degree radiation angle). As you angle the radials down, this lobe gets stronger.
When it comes to radiation efficiency, angling the radials down also drops the antenna's overall radiation efficiency. The difference between the horizontal radials model and the model with the radials angled down from horizontal to 60 degrees down is about 6%. Again, not enough in and of itself to be noticed.
One other thing to look at is the impedance matching results. In this case, R and SWR at resonance.
Horizontal radials show an R of 22.9, and an SWR of 2.18
Angling the radials down causes R to go up, and SWR drops to its low point at about 45 degrees. Angle the radials further than that and SWR starts going up again.
If you are someone who cares about SWR, the only real benefit to angling radials down is the lower SWR you can get. If, however, you are one of us that don't really care about SWR, as long as it is "close enough", then just adding a slight angle will be enough.
I want to point out that this is for a 1/4 wavelength vertical antenna, if you are talking about radials on a 5/8 wavelength antenna, downward angled radials can actually work against the antenna. If you want to see angled radials put on a 5/8 wavelength antenna model, ask and I will make some models for you.
The DB
The 0 model is horizontal, the other numbers are that many degrees below horizontal.
These models are mounted 18 feet above the earth. I also tuned all of them to resonance and did it in such a way that the vertical elements were the exact same length as the radial elements in the individual models.
Essentially, when it comes to gain, horizontal radials provides the most low angle (in this case 15 degree radiation angle) gain, and as you angle the radials down, that gain drops. However, you won't notice a difference in gain as the worst angle has -0.29 dB less gain from the model with horizontal radials. The more I angled the radials down the less gain the model had.
It should be noted that the exact opposite is happening with the higher angle lobe (up at the 45 degree radiation angle). As you angle the radials down, this lobe gets stronger.
When it comes to radiation efficiency, angling the radials down also drops the antenna's overall radiation efficiency. The difference between the horizontal radials model and the model with the radials angled down from horizontal to 60 degrees down is about 6%. Again, not enough in and of itself to be noticed.
One other thing to look at is the impedance matching results. In this case, R and SWR at resonance.
Horizontal radials show an R of 22.9, and an SWR of 2.18
Angling the radials down causes R to go up, and SWR drops to its low point at about 45 degrees. Angle the radials further than that and SWR starts going up again.
If you are someone who cares about SWR, the only real benefit to angling radials down is the lower SWR you can get. If, however, you are one of us that don't really care about SWR, as long as it is "close enough", then just adding a slight angle will be enough.
I want to point out that this is for a 1/4 wavelength vertical antenna, if you are talking about radials on a 5/8 wavelength antenna, downward angled radials can actually work against the antenna. If you want to see angled radials put on a 5/8 wavelength antenna model, ask and I will make some models for you.
The DB
Good post DB thanks for the models.
Confirms how the starduster type antenna work.
Direct feed no matching network.
Nothing mentioned on the ground radials eliminating CMC or contributing to CMC.
did you happen to model a feed line and mast also?
Confirms how the starduster type antenna work.
Direct feed no matching network.
Nothing mentioned on the ground radials eliminating CMC or contributing to CMC.
did you happen to model a feed line and mast also?
Yes there is. Plus, I know I have said this before if a manufacturer can shave a nickle off of the cost building it they will. Look at all of the additional hardware and design to get all of it to hold together. It was not done just to make it pretty.
Actually, a lot of antennas have been sold because of the looks.
there is no reason for 4 radials @ 90 degrees, 2 @ 180 work just as well
https://www.w8ji.com/ground_plane_verticals.htm
https://www.w8ji.com/VHF mobile vertical.htm
https://www.w8ji.com/end-fed_vertical.htm
Some good reading especially comparing 1/4 wl, 1/2 wl, 5/8 wl verticals
https://www.w8ji.com/VHF mobile vertical.htm
https://www.w8ji.com/end-fed_vertical.htm
Some good reading especially comparing 1/4 wl, 1/2 wl, 5/8 wl verticals
1. Below are two overlays of my 1/4 wave vertical StarDuster like antenna with horizontal radials, no mast, and no feed line included in the model.
I set each model to resonance similar to the way DB suggested he did as he changed the radial angles.
The antenna is also set 18' feet above ground, but my model is set with the Ground Description set to Average Soil.
Each model is also set similar to what DB did with radials slanted down at 15,30,45,60 degrees and is noted in the color descriptions listed.
I uses the same models and simply changed the soil condition settings to Extremely Poor in order to try and get my patterns to look more similar to DB's presentations.
2. The second PDF file is the starting model with 3 horizontal radials which includes added performance details and antenna images. Note that these two models with horizontal radials both show similar matching results compared to DB's starting model.
The models are set over Average Soil and Extremely Poor Soil as a comparison to the effects that soil settings have on the patterns and gain produced.
This said, I cannot explain why my models show producing a steadily increasing trend in gain as the radials are set at lower angles. This is the opposite trend we see in DB's models.
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I'm currently using a Starduster type set-up. I have one of the Workman hubs. I'm using a 102" Radio Shack stainless steel whip as my vertical radiator. The hub has slots for 3 ground radials. I am using 3 of the 102" Radio Shack stainless steel whips in that role, too. The itself hub screws right onto the threaded galvanized plumbing pipe that I am using for a mast.
It works. No tuning network needed. Excellent skip, but the local communications are definitely not as strong as with the IMAX 2000.
It works. No tuning network needed. Excellent skip, but the local communications are definitely not as strong as with the IMAX 2000.
I am using an starduster, not the m400 version.
compared to my imax the starduster receives better and transmits better.
As rick posted direct feed but I am using the original configuration and no modifications for elements.
I can not explain why the starduster outperforms the imax.
Not a big difference no such thing as an S unit difference, not even 1/2 s unit.
Over months of comparing the two antennas the starduster seems to be more sensitive to weak signals. I can have a qso on the starduster, I can not even hear them on the imax.Again this is weak signal, not moving the S meter and only hearing audio.
I can not explain this nor will I attempt to. just throwing out my observations and opinions.
compared to my imax the starduster receives better and transmits better.
As rick posted direct feed but I am using the original configuration and no modifications for elements.
I can not explain why the starduster outperforms the imax.
Not a big difference no such thing as an S unit difference, not even 1/2 s unit.
Over months of comparing the two antennas the starduster seems to be more sensitive to weak signals. I can have a qso on the starduster, I can not even hear them on the imax.Again this is weak signal, not moving the S meter and only hearing audio.
I can not explain this nor will I attempt to. just throwing out my observations and opinions.
waverider,
w8ji explains why a starduster can outperform an imax,
https://www.w8ji.com/end-fed_vertical.htm#IMAX
it also explains why some people swear by their imax 2000 while others swear whenever somebody mentions imax or a99,
i have seen with my own eyes what isolation + radials can do for the imax & a99 on some installs.
w8ji explains why a starduster can outperform an imax,
https://www.w8ji.com/end-fed_vertical.htm#IMAX
it also explains why some people swear by their imax 2000 while others swear whenever somebody mentions imax or a99,
i have seen with my own eyes what isolation + radials can do for the imax & a99 on some installs.
Sold to the targeted gullible demographic crowd that use "Fat Watts." Two radials at 180 degrees?
My M400 is pole mounted with the feed point right at 18 feet. I made my very first International ham radio contact using the M400 and my HR2510 bare foot. The contact was made to an island in the Atlantic off of the coast of Spain. It was not the Azores.
The operator thought I was local pulling his leg.