|
Radial wire
As I continue my slow study of vertical antennas I am nearing the
point where I need to plan a radial system. It is no big surprise that Everything I am doing has been done before but this is intended to be a learning experience. The red North Carolina clay varies widely with the seasons, I hope to be ready when the ground softens up to where I can bury the radials. The current plan is to build a mechanism that will allow me to do the job from the seat of my tractor. I would prefer to not use fence staples because I expect they would forever plague me in my tractor tires. The question: I seem to be the only one inclined to use electric fence wire for radials. I know from experience that the galvanized steel 17 ga will last in excess of 10 years. I have found the Aluminum to be lacking in strength when I use it for antenna experiments. Both are available for less than $45 per mile. My notes on the project are at http://dixienc.us/28FtVert/28FtVertical.htm The second page is recent. Not much "meat" for the guru's, but may be interesting reading or reference links for the curious. John Ferrell W8CCW |
Radial wire
Hi, John.
You seem to be confusing radial wires with ground screen wires. Radial wires must be insulated from the ground because they need to be specific lengths for the frequency they are cut for. The ground screen is made of non-inslated wires on the ground surface, or buried slightly under it. I think the "staples" you are refering to are just wire "hair pins" to hold the wire in contact with the soil. Where you live, grass, etc. should grow over the wire in no time! Here in the desert, rocks are used to hold the wire down. There was a commercial AM radio transmitter/tower behind my place. I salvaged many hundreds of feet of #16 bare copper wire from their ground screen. It was just under the surface and held in place with lava rocks. The tower base was concrete with 8" wide copper flashing between the base and the tower. It was soldered to a copper mesh around the concrete base. The ground screen wires were just twisted into the copper mesh. Our neighbor said the whole thing was a wonderful lightening rod!!! Paul, KD7HB Redmond, OR John Ferrell wrote: As I continue my slow study of vertical antennas I am nearing the point where I need to plan a radial system. It is no big surprise that Everything I am doing has been done before but this is intended to be a learning experience. The red North Carolina clay varies widely with the seasons, I hope to be ready when the ground softens up to where I can bury the radials. The current plan is to build a mechanism that will allow me to do the job from the seat of my tractor. I would prefer to not use fence staples because I expect they would forever plague me in my tractor tires. The question: I seem to be the only one inclined to use electric fence wire for radials. I know from experience that the galvanized steel 17 ga will last in excess of 10 years. I have found the Aluminum to be lacking in strength when I use it for antenna experiments. Both are available for less than $45 per mile. My notes on the project are at http://dixienc.us/28FtVert/28FtVertical.htm The second page is recent. Not much "meat" for the guru's, but may be interesting reading or reference links for the curious. John Ferrell W8CCW |
Radial wire
Hi John,
John W8CCW wrote: The red North Carolina clay varies widely with the seasons, I hope to be ready when the ground softens up to where I can bury the radials. The current plan is to build a mechanism that will allow me to do the job from the seat of my tractor. I would prefer to not use fence staples because I expect they would forever plague me in my tractor tires. I've never had a problem with the large garden staples getting into tractor tires. If you are really concerned, you could probably get away with one staple at the very end of each radial and then remove it after the thatch grows over the radial. I would never go to the trouble of buring radials myself. I now have about 130 ranging in length from 70' to 150' under my 180' tower for my 160 system. If you still want to bury your radials here's a neat idea by SM2CEW: http://www.sm2cew.com/plow.htm The question: I seem to be the only one inclined to use electric fence wire for radials. I know from experience that the galvanized steel 17 ga will last in excess of 10 years. I have found the Aluminum to be lacking in strength when I use it for antenna experiments. Both are available for less than $45 per mile. I put down about 10 rolls of welded galvanized mesh fencing (3-4' width by about 50-100') under my tower in 1997. Those rolls completely rusted several years ago and I disconnected them recently. My soil is mostly red clay (QTH is NC also) with some sandy loam areas. In my case the mesh was probably overkill anyway since my radial field alone is sufficient close to the tower. I have used galvanized wire for Beverages and it lasts forever when suspended in air...but that was not my experience with it on the ground. Aluminum is also not a good choice because of interaction with acid in the soil. Copper is best but the prices have now skyrocketed so much I can understand why you are looking for other alternatives. Good luck with your project! 73, Bill W4ZV |
Radial wire
On 27 Oct 2006 09:31:16 -0700, wrote:
I've never had a problem with the large garden staples getting into tractor tires. If you are really concerned, you could probably get away with one staple at the very end of each radial and then remove it after the thatch grows over the radial. I would never go to the trouble of buring radials myself. I now have about 130 ranging in length from 70' to 150' under my 180' tower for my 160 system. If you still want to bury your radials here's a neat idea by SM2CEW: http://www.sm2cew.com/plow.htm The question: I seem to be the only one inclined to use electric fence wire for radials. I know from experience that the galvanized steel 17 ga will last in excess of 10 years. I have found the Aluminum to be lacking in strength when I use it for antenna experiments. Both are available for less than $45 per mile. I put down about 10 rolls of welded galvanized mesh fencing (3-4' width by about 50-100') under my tower in 1997. Those rolls completely rusted several years ago and I disconnected them recently. My soil is mostly red clay (QTH is NC also) with some sandy loam areas. In my case the mesh was probably overkill anyway since my radial field alone is sufficient close to the tower. I have used galvanized wire for Beverages and it lasts forever when suspended in air...but that was not my experience with it on the ground. Aluminum is also not a good choice because of interaction with acid in the soil. Copper is best but the prices have now skyrocketed so much I can understand why you are looking for other alternatives. Good luck with your project! 73, Bill W4ZV I am looking for the easiest way out for me! I mow the three acres of grass with a small Ford Farm tractor and a belly mower. It is seldom cut really short but I still fear picking up the wire in the mower. I have used home brew wire staples when I lived in Ohio but this soil is pretty tough for that. The SM2CEW Plow is what inspired me to consider burying the wire to begin with. I think it likely that I am considering more radials than are practical anyway. 500 feet of #14 insulated wire was less than $25 the last time I bought it. John Ferrell W8CCW |
Radial wire
John Ferrell wrote: I am looking for the easiest way out for me! I mow the three acres of grass with a small Ford Farm tractor and a belly mower. It is seldom cut really short but I still fear picking up the wire in the mower. I have used home brew wire staples when I lived in Ohio but this soil is pretty tough for that. The SM2CEW Plow is what inspired me to consider burying the wire to begin with. Mow it as low as possible when the grass is dormant, put down the radials, staple them and then let the grass grow as high as possible before mowing at a medium height. If you put the radials down now, I suspect they will mostly pack down before the grass starts growing again in the spring, especially if we get a couple of snow or ice storms. I think it likely that I am considering more radials than are practical anyway. 500 feet of #14 insulated wire was less than $25 the last time I bought it. Here's a simple formula to save you money since I've heard that same roll of wire is now around $45! No matter how long your radials are, put the ends down such that they are ~0.025 wavelengths apart on the highest frequency band you plan to use. On 160 this is ~13', on 80 6.5' and on 40 3.25'. This works out to about 63 radials total if they are all 1/4 wavelengths long in a circular configuration, but the formula also works for random lengths in non-circular configurations. The idea is to have the end points no more than ~0.025 wavelengths apart. While ON4UN's book suggests 0.015 wavelengths apart, some recent measurements by N6LF seem to indicate that may be overkill (i.e. 60 radials are within a few tenths of a dB of 120 radials). http://www.antennasbyn6lf.com/files/...asurements.pdf 73, Bill W4ZV |
Radial wire
Here's a simple formula to save you money since I've heard that same roll of wire is now around $45! No matter how long your radials are, put the ends down such that they are ~0.025 wavelengths apart on the highest frequency band you plan to use. On 160 this is ~13', on 80 6.5' and on 40 3.25'. This works out to about 63 radials total if they are all 1/4 wavelengths long in a circular configuration, but the formula also works for random lengths in non-circular configurations. The idea is to have the end points no more than ~0.025 wavelengths apart. While ON4UN's book suggests 0.015 wavelengths apart, some recent measurements by N6LF seem to indicate that may be overkill (i.e. 60 radials are within a few tenths of a dB of 120 radials). http://www.antennasbyn6lf.com/files/...asurements.pdf 73, Bill W4ZV At $45/500 feet it is still a long way from Cost prohibitive. Do I misunderstand? My intuition is to place the radials I use over as much area as I can. The way I read your note is that they should be installed in a small sector... I think I am misunderstanding that point. Also, on the distant planning horizon I will likely use the Radial field for a permanent Multi band Vertical. The current 28 foot radiator is simply a convenient place to gain experience. I am inclined to pursue the advice presented in the article http://www.ncjweb.com/k3lcmaxgainradials.pdf John Ferrell W8CCW |
Radial wire
|
Radial wire
John Ferrell wrote: Do I misunderstand? My intuition is to place the radials I use over as much area as I can. The way I read your note is that they should be installed in a small sector... I think I am misunderstanding that point. You want to cover the maximum area...but using the minimum amount of wire to do so effectively...which is what 0.025 wavelengths spacing between the endpoints yields. I am inclined to pursue the advice presented in the article http://www.ncjweb.com/k3lcmaxgainradials.pdf The problem with all of K3LC's articles is that he only uses NEC-4 modeling with no empirical measurement data. N6LF's article below compares his measurements to the same NEC-4 model (see Figure 5 and last paragraph on page 5). Modeling programs are notorious for poorly handling radials on ground. Although NEC-4 is supposedly the best for this, the results N6LF reported (i.e. NEC-4 saying no improvement for more than 16 radials) are inconsistent with all measurement data going back to the 30's (including that used by the FCC for broadcast station commissioning). http://www.antennasbyn6lf.com/files/...asurements.pdf (see Fig. 5 & bottom paragraph, p. 5) 73, Bill W4ZV |
Radial wire
The problem with all of K3LC's articles is that he only uses NEC-4 modeling with no empirical measurement data. N6LF's article below compares his measurements to the same NEC-4 model (see Figure 5 and last paragraph on page 5). Modeling programs are notorious for poorly handling radials on ground. Although NEC-4 is supposedly the best for this, the results N6LF reported (i.e. NEC-4 saying no improvement for more than 16 radials) are inconsistent with all measurement data going back to the 30's (including that used by the FCC for broadcast station commissioning). http://www.antennasbyn6lf.com/files/...asurements.pdf (see Fig. 5 & bottom paragraph, p. 5) 73, Bill W4ZV I appreciate your patience and guidance. The current 28 foot radiator is poorly located to invest too much labor and materials for a permanent radial field. This location will only permit 270 degrees of radials. It seems prudent to locate the permanent field where I can get at least 0.125 wave length radials at 160m with a minimum of 16. Although it will complicate things by requiring additional coax and a longer run of #6 ground wire to include it in the lightning protection system I think it will be worth it. That plan will also allow additional longer radials in the future. John Ferrell W8CCW |
| All times are GMT +1. The time now is 08:24 AM. |
Powered by vBulletin® Copyright ©2000 - 2025, Jelsoft Enterprises Ltd.
RadioBanter.com