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#1
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Use of ground wires underneath dipoles
According to Wikipedia
(http://en.wikipedia.org/wiki/Near_Ve...dence_Skywave), a horizontally-polarized NVIS antenna will benefit from a ground wire underneath it. Here's an excerpt: "An NVIS antenna configuration is a horizontally polarized (parallel with the surface of the earth) radiating element that is from 1/20th wavelength ... to 1/8th wavelength above the ground. That proximity to the ground forces the majority of the radiation to go straight up. Overall efficiency of the antenna can be increased by placing a ground wire slightly longer than the antenna parallel to and directly underneath the antenna. While the ground wire is not necessary under good to excellent propagation conditions, antenna gain in the 3 dB to 6 dB range are common when the ground wire is used." Since I've never heard of anyone doing this, or seen any hams trying it, I'd like to hear from those who've done it, and find out if the gain is as predicted. 73, Bill W1AC, who is rushing to get a good sky-hook up before the winter -- Bill Horne (Remove QRM from my address for direct replies.) |
#2
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Use of ground wires underneath dipoles
On Tue, 30 Sep 2008 18:39:02 EDT, Bill Horne wrote:
According to Wikipedia (http://en.wikipedia.org/wiki/Near_Ve...dence_Skywave), a horizontally-polarized NVIS antenna will benefit from a ground wire underneath it. Here's an excerpt: "An NVIS antenna configuration is a horizontally polarized (parallel with the surface of the earth) radiating element that is from 1/20th wavelength ... to 1/8th wavelength above the ground. That proximity to the ground forces the majority of the radiation to go straight up. Overall efficiency of the antenna can be increased by placing a ground wire slightly longer than the antenna parallel to and directly underneath the antenna. While the ground wire is not necessary under good to excellent propagation conditions, antenna gain in the 3 dB to 6 dB range are common when the ground wire is used." Since I've never heard of anyone doing this, or seen any hams trying it, I'd like to hear from those who've done it, and find out if the gain is as predicted. I have a chain-link fence along my property line. Maybe I can move my antenna over to the property line and use the fence as ground wire. 73, Bill W1AC, who is rushing to get a good sky-hook up before the winter 73, Dick, AC7EL in Southern Nevada, who is waiting for November or later to do his antenna work. It was 95 degrees Fahrenheit today, still too hot for outdoor work for this transplanted New Hampshirite. BTW, it almost never snows here. 73 de Dick, AC7EL |
#3
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Use of ground wires underneath dipoles
"Bill Horne" wrote in message t... According to Wikipedia (http://en.wikipedia.org/wiki/Near_Ve...dence_Skywave), a horizontally-polarized NVIS antenna will benefit from a ground wire underneath it. Ever hear of a 2 element Yagi? |
#4
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Use of ground wires underneath dipoles
In article ,
Bill Horne wrote: According to Wikipedia (http://en.wikipedia.org/wiki/Near_Ve...dence_Skywave), a horizontally-polarized NVIS antenna will benefit from a ground wire underneath it. Here's an excerpt: "An NVIS antenna configuration is a horizontally polarized (parallel with the surface of the earth) radiating element that is from 1/20th wavelength ... to 1/8th wavelength above the ground. That proximity to the ground forces the majority of the radiation to go straight up. Overall efficiency of the antenna can be increased by placing a ground wire slightly longer than the antenna parallel to and directly underneath the antenna. While the ground wire is not necessary under good to excellent propagation conditions, antenna gain in the 3 dB to 6 dB range are common when the ground wire is used." Since I've never heard of anyone doing this, or seen any hams trying it, I'd like to hear from those who've done it, and find out if the gain is as predicted. 73, Bill W1AC, who is rushing to get a good sky-hook up before the winter We used a configuration of that principal, for years, when doing communications for the Ididarod DogSled Races out in the bush of Alaska. Put up a Dipole for 80 Meters, strung between the trees, and then ran a Grounded Wire, directly under the Dipole, that was 3% longer, electrically. Increased our ERP for Short Range Comms. Typical Ranges were from 120-500 Miles. KL7BB can give you any details, you could require, if you can track Crazy Bill down...... |
#5
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Use of ground wires underneath dipoles
Dick Grady AC7EL wrote:
73, Dick, AC7EL in Southern Nevada, who is waiting for November or later to do his antenna work. It was 95 degrees Fahrenheit today, still too hot for outdoor work for this transplanted New Hampshirite. BTW, it almost never snows here. 73 de Dick, AC7EL et tu, Brute? -- Bill Horne (Remove QRM from my address for direct replies.) |
#6
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Use of ground wires underneath dipoles
You wrote:
In article , Bill Horne wrote: According to Wikipedia (http://en.wikipedia.org/wiki/Near_Ve...dence_Skywave), a horizontally-polarized NVIS antenna will benefit from a ground wire underneath it. [snip] Since I've never heard of anyone doing this, or seen any hams trying it, I'd like to hear from those who've done it, and find out if the gain is as predicted. We used a configuration of that principal, for years, when doing communications for the Ididarod DogSled Races out in the bush of Alaska. Put up a Dipole for 80 Meters, strung between the trees, and then ran a Grounded Wire, directly under the Dipole, that was 3% longer, electrically. Increased our ERP for Short Range Comms. Typical Ranges were from 120-500 Miles. KL7BB can give you any details, you could require, if you can track Crazy Bill down...... What puzzles me is the ground: I don't understand why such a wire would function as anything but, well, ground. I understand that it's a parasitic reflector if not grounded (has anyone tried this?), but I don't get the reason for the ground. BTW, is it grounded at both ends? 73, Bill W1AC -- Bill Horne (Remove QRM from my address for direct replies.) |
#7
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Use of ground wires underneath dipoles
On Oct 2, 12:58 am, Bill Horne wrote:
What puzzles me is the ground: I don't understand why such a wire would function as anything but, well, ground. I I think it's really about ground (dirt) conductivity. Which varies all over the place. In some places (moist, loamy soil with lots of minerals, coastal areas where the water table is very high and salty) the dirt is a pretty good conductor, to the point where antennas "worked against ground" do pretty well with just a ground rod or two. RF just bounces off that sort of dirt. In other places (dry, sandy, rocky soil) the dirt is a very lossy counductor, and acts more as an RF absorber. With a low dipole, the ground is so close that it has major effects on the antenna. If it's lossy dirt, it just soaks up RF, but if it's a decent conductor, it can act as a reflector. The added wire is just a way of improving the ground conductivity in the dirt that is most involved: the dirt directly under the antenna. 73 de Jim, N2EY |
#8
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Use of ground wires underneath dipoles
Hi O,m's
interresting things around here about groundwires at a dipole in my reply of the 3.5mc vertical i told that an antenna can bee seen as a coil and a condensor tuned at working frequencie a run of wire has an inductance remind the stripline tuned circuit at vhf if we have a normal tuned circuit coil and capacitance it is understandable we see the parts if the coil is a length of wire a litle less but if we remind uhf circuits if we move the condensorplates to the top and bottom of the coil we can see still the tuned circuit and we have a new experimental antenna type google H antenna for more details also commercial available even precooked building instructions very interresting to understand the basics of antennatheory if we strech the coil we got the wireantenna where is the condensator hi the wiresurface to earth now we can understand that the dipole is a serial combination of two coils and 2 condensators and a thirdth to earth notice that there are 2 radiation paterns a magnetic from the coil and a statthic from the condensator so it is to understand that a groundwire under the dipole has an influance at the capacity of the antenna and also at its radiation the groundconditions of our garden chances rain moisture sun etc the condition of the diged wire will not chance and the results of the antenne too. i hope i cleared a little 73 de ruud PA0RAB schreef in bericht ... On Oct 2, 12:58 am, Bill Horne wrote: What puzzles me is the ground: I don't understand why such a wire would function as anything but, well, ground. I I think it's really about ground (dirt) conductivity. Which varies all over the place. In some places (moist, loamy soil with lots of minerals, coastal areas where the water table is very high and salty) the dirt is a pretty good conductor, to the point where antennas "worked against ground" do pretty well with just a ground rod or two. RF just bounces off that sort of dirt. In other places (dry, sandy, rocky soil) the dirt is a very lossy counductor, and acts more as an RF absorber. With a low dipole, the ground is so close that it has major effects on the antenna. If it's lossy dirt, it just soaks up RF, but if it's a decent conductor, it can act as a reflector. The added wire is just a way of improving the ground conductivity in the dirt that is most involved: the dirt directly under the antenna. 73 de Jim, N2EY |
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