Sorry, Jason, but you did ask if money were no object....
That means you can buy a new yard 😆
Buried copper radial wires (radials) have a very different effect on AM propagation than other types of grounding systems. That is because of the way the radials actually interact with the antenna. When I said you can never have too much grounding, I really meant to say that you can never have too many buried copper radial wires, at least until you reach 360 of them.
I recall reading on some forums about dramtic range increases with 60 or more buried copper radial wires. A mesh just won't interact with the antenna like a lot of buried copper radial wires.
I know you don't want to spring for the rangemaster, but check out some of their testimonials and see if you can track down the real stations using their sync'd transmitter system. The url is:
http://www.am1000rangemaster.com/
The following post on this forum has some other goodies:
There is a citation by tregonsee about the rangemaster's specs calling for at least 64 buried radials of #12 ga. copper wire.
I don't see how to get away from not having radials for the range itch that you have.
You can try some searches on the Rangemaster on this forum and other parts of the internet to see if you can come up with additional info on syncing multiple p15 AM transmitters. I have seen them in the past, but can't find links right now.
I placed my antenna up next to my house, so that would limit me from having 360 degrees of ground radials.
Must ground radials be placed symmetrically? I seem to recall reading something about that. I'd probably be able to get them 120-150 degrees around my antenna, out into the yard running away from the house.
Does anyone have any experience with this? Or would I be better off with simple grounding rods?
Many thanks,
Scott
If money truly was no object, a few acers of land and radial strethcing man mnay feet and 360 of them would be great...
I wil upgrade my radial to probably 60 or more.. as long as i can make them.. But it will have to wait till next year...
I would love a rangemaster, but truly money is a object in my book.. so its best bang for the buck here..
I feel i tmay be easier to lay out a ton of radials then have a few dumptrucks of dirt to spread over it all... Thoughts?
HAs nay one determined if dept makes a idffrence for radials?
Jason
Must ground radials be placed symmetrically? I seem to recall reading something about that. I'd probably be able to get them 120-150 degrees around my antenna, out into the yard running away from the house.
Yes Scott, they have to be symetrical to obtain the optimal, desired propagation characteristics. Even on commerical phased arrays that have multiple antennas, the radials are symetrical around each antenna within the array.
I feel i tmay be easier to lay out a ton of radials then have a few dumptrucks of dirt to spread over it all... Thoughts?
Jason, many years ago I heard about a fellow who was putting up a new AM commercial station. He and an employee hand laid all 360 buried copper radials with a type of hand trenching tool. I am not "handy" enough at outdoor tools to know what it was. I also have no idea how long it took.
I believe that "Invisible Fence" (TM), which is a buried copper wire system for activating dog training collars is hand laid with a special type of trenching tool that basically pushes the wire a few inches under the top of the topsoil. While I have never seen the actual tools they use, the lawns look pretty good shortly after installation, so it probably isn't too "invasive."
That dog fence tool sound like a good idea, any one know what this is called, and where to get them...
My neighbor has the invisable fence thing for her dogs.. And your right its not invasive and i think they fenced here entire yard in a few hours.. THats pretty fast to burrry a fence line around a entire double city lot (about 1/2 acer)..
Very good idea, actually i wonder if there fence line is copper and if it would be suitable for radials.. heck you could hire the fence guy to run you 60 or so radials say 30 foot long, and it could probably be done quickly and not cost to much and i would actually be willing to hire some one for a few hours to gun me a killer gound radial system... Hmm I will have to talk to my neighbor some time.. see if sh can give me the guys number.. see if he would be willing to do this..
IM going to search around for this tool..
Jason
OK Radio Fence,says a power lawn edger works well...
This is a little two stroke motor or electric notod with a cutting bat its normally used to trim the edge of your walk or drive from the greass that is growing over the edge.. thus the name a edger...
I have seen these they dig a trench about 2 inches deep in the the lawn between a 1/4 and a1/2 inches wide.. perfect for a ground radial... HMMM if you mounted a spool and made a way for the spool to unroll as you went you could trench and burry radials all day with very little effort... HMM Very interesting... THis would make placing your ground system very quick and make ing a huge system would be very easy..
I also found that radio fence is actually aliminum... 17 gauge...
I would assume we want to stick with copper and go with a lower gauge (thicker) wire than that.. any thoughts?
I may have to buy a edger and give it a shot next year Heck if i hurried up i could do it this year..
Jason
Must ground radials be placed symmetrically? I seem to recall reading something about that. I'd probably be able to get them 120-150 degrees around my antenna, out into the yard running away from the house.
Yes Scott, they have to be symetrical to obtain the optimal, desired propagation characteristics. Even on commerical phased arrays that have multiple antennas, the radials are symetrical around each antenna within the array.
Hi RadioheadC:
If I can't lay radials symmetrically, would I be better off not using them at all, but rather, focus on a good grounding rod system? I have two eight-foot rods now, and I could probably go as high as eight arond the mast.
Thanks,
Scott
That dog fence tool sound like a good idea, any one know what this is called, and where to get them...
As I said in my post it is called "Invisible Fence" (TM). Invisible Fence is the brand name and the website is www.invisible fence.com
If you Google "invisible fence" you will come up with lots of their kniock off competitors like Radio Fence andn others. Good luck! (And please send us some pictures of your torn up yard!)
If I can't lay radials symmetrically, would I be better off not using them at all, but rather, focus on a good grounding rod system? I have two eight-foot rods now, and I could probably go as high as eight arond the mast
Scott,
I don't know what a "sub-optimal" asymetric radial pattern would do. There may be some RF wizards on this forum who can model this.
Very good idea, actually i wonder if there fence line is copper and if it would be suitable for radials.. heck you could hire the fence guy to run you 60 or so radials say 30 foot long, and it could probably be done quickly and not cost to much and i would actually be willing to hire some one for a few hours to gun me a killer gound radial system...
Jason,
I don't know whether or not 30 feet is the appropriate length for the radials with a Part 15 antenna. I would assume that the length of the radial, relative to the antenna length would have an impact on the AM signals propagation characteristics. (Like how far out it will go.) There was some discussion of the appropriate length in another thread on this forum some time ago. Sorry, but I can't remember when and I can't point you to it.
Must ground radials be placed symmetrically? I seem to recall reading something about that. I'd probably be able to get them 120-150 degrees around my antenna, out into the yard running away from the house.
Radial ground wires provide a low resistance path for the currents induced in the nearby earth from radiation by the antenna. This is important to have, because the resistance in this connection is in series with the r-f current in the antenna. The current flowing through the ground resistance consumes power that could otherwise be radiated by the antenna, which reduces the radiation efficiency of the antenna system.
Here are some numbers showing the effects of a radial ground system on received field strength, based on carefully measured data. Frequency is 1.7 MHz, radial length is 80 feet (0.137 wavelengths). The reference field is that produced by a 1/4-wave vertical with about 120 symmetrically arranged radials, each 0.41 wavelengths long.
Number of Radials > % of Ref. Field
2 > 9.5
15 > 16.8
30 > 20
60 > 22
So using 30 radials in this situation increases distant field strength to more than double that when using 2 radials. To double field strength when using 2 radials, the transmitter power would need to increased by four times. (All comments assume other things are equal.)
The most important benefit of the ground system is to reduce ground losses for the antenna system. Asymmetric placement of the radials around the base of the radiator isn't ideal, but if the radials that [b:30eaeef90e]can[/b:30eaeef90e] be installed minimize ground losses for a given installation, that will maximize the radiation efficiency of the antenna system for that situation.
The feedpoint impedance of the antenna system will change after installing a radial ground system. The resistance term should be lower, and the tuning/matching circuits of the transmitter may need to be optimized for maximum power transfer for the new conditions.
BTW, a cold water pipe ground or "ground stake" is not a very effective MW ground no matter what the length. There is little r-f current induced in the earth beyond about 1/2-wavelength from the radiator and most of it is flowing near the surface, horizontally back toward the radiator. So the only lengths that collect any ground currents from the antenna are within that area.
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Hi, Rich.. (Gonna pick your brain a little)
Let's assume that a PART-15 Legal antenna is a 1/4 wavelength radiator and one has an area where a 120 radial ground system can be installed..
Is 0.41 wavelength/per freq on the ground radial length pretty much "standard" or is there a more efficent length that could be considered?
I seen on one of your graphs using a 20' level above the ground area for good results. (as for outer field strength) Would there be a better heigth above a "good" or "efficient" ground system that could give maximum or best possible performance?
Is 0.41 wavelength/per freq on the ground radial length pretty much "standard" or is there a more efficent length that could be considered?
Using 120 radials each at least 0.41 wavelengths long with a 1/4-wave vertical will produce a field strength at 1 mile that is within a few percent of the theoretical maximum for a zero-loss ground connection.
If that same radial ground system is used with a 3 meter, ground-mounted radiator operating on 1.7 MHz, the field strength at 1 mile will drop to about 82% of the value produced by a 1/4-wave radiator (other conditions equal). Note that this is the effect of the reduced radiation resistance of the very short radiator, only. It does not include the losses of the matching components needed to couple maximum available tx power into that radiator.
Using longer that 0.41-wave radials probably isn't justified for the small additional coverage benefit they would add to a system of 120 radials. But if fewer radials are used, they can be shortened, because using fewer radials reduces their effective length.
I seen on one of your graphs using a 20' level above the ground area for good results. (as for outer field strength) Would there be a better heigth above a "good" or "efficient" ground system that could give maximum or best possible performance?
The field strength improvement in the graph you mentioned was due to the added electrical length of the "Part 15" radiator when mounting the 3 meter portion and tx 6 meters above ground, and connecting the tx chassis to earth ground by a conducting path (some combination of a ground lead/ground wire/tower).
The longer-than-3-meter antenna created this way has higher radiation resistance than the legal 3-meter antenna, which means that a greater percentage of the available power is actually radiated rather than being lost in the ground system as heat.
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Thanks, Rich..
I'm begining to get a grasp on this MW stuff..
Since we have been discussing "directional" antennas, Gonna pick your brain again.. 💡
Let's say that only 1/4 of a ground array was laid out from a central point (like a 1/4 of a pie..30 radials.. or more) at 0.41 wavelength per frequency. Would the antenna react to the area of the less resistance (ground resistance) and cause a lobe in the direction of that area.. making it somewhat directional? Would the majority of the radiated power be drawn towards the ground area?
Thanks in advance.. 😉
Let's say that only 1/4 of a ground array was laid out from a central point (like a 1/4 of a pie..30 radials.. or more) at 0.41 wavelength per frequency. Would the antenna react to the area of the less resistance (ground resistance) and cause a lobe in the direction of that area.. making it somewhat directional? Would the majority of the radiated power be drawn towards the ground area?
Repeating what I wrote a few posts earlier in this thread, "the most important benefit of the ground system is to reduce ground losses for the antenna system. Asymmetric placement of the radials around the base of the radiator isn't ideal, but if the radials that can be installed minimize ground losses for a given installation, that will maximize the radiation efficiency of the antenna system for that situation."
If the radials are missing over some sector, that will increase total ground system losses -- meaning that less power is available to be radiated by the antenna. But that will reduce radiation in all directions, not just where the radials are missing.
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