# Tag Info

12

If anything, living in an area with high metal deposits near to the ground will improve your conditions by improving the conductivity of your ground. That said, unless it's very near to the surface and high concentration, I doubt you'd notice any difference. Note that when we model the ground as an ideal ground plane, anything underground has no impact on ...

9

There is a special adaptation of the Friis equation, called the Radar Equation, that describes the range of a radar system. Here is a basic version that calculates the maximum range of a radar system: $$R_{max}=\sqrt[4] {\frac {P_tG^2\lambda^2\sigma}{P{_{r(min)}}*(4\pi)^3*L}} \tag 1$$ where $R_{max}$ is the maximum range in meters, $P_t$ is the transmit ...

9

Other Effects are there any other geological properties that can affect radio waves? Yes, there are other effects. Basically, every material affects the propagation of radio waves. Absorption That one's kind of obvious: radio wave hits medium (e.g. soil), gets absorbed. That's the reason you can't look through a piece of coal – light is just a wave at a ...

7

With the canal 60 feet away it's not of much help. The objective with a monopole antenna is not just to have any ground connection, but to have a low-loss ground plane under the base of the antenna. The ground plane provides the return current and creates an image antenna. The return current density is highest where it converges at the base of the antenna. ...

6

The number of horizontal radial wires used in an elevated "counterpoise" can be far fewer than the 120 buried wires used by most AM broadcasters, and the even fewer numbers of buried wires often used with vertical monopoles, inverted Ls etc by amateur radio operators. Several AM broadcast stations use 3 or 4 pairs of λ/4, co-linear, horizontal radial wires ...

5

The purpose of the counterpoise is to provide an efficient means of conducting the return RF current of the antenna. In the absence of an efficient counterpoise, the current will return through the lossy earth or poorly quantified paths such as coaxial cable shields. An efficient counterpoise will carry the same current as the primary radiating element. A ...

5

Larger wire will have less resistance. However, the resistance of the radials in either case is negligible compared to the soil resistance, so I wouldn't worry about it. Longevity would be my concern. Commercial broadcast towers use 10 gauge bare wire. Anecdotally, there are plenty of amateurs happily using 18 gauge wire. Corrosion depends on many factors. ...

4

It is well-established that a wire reflector --on or just above the ground-- directly under a dipole can do just that. I don't have a reference, but at a field day that I was present at years ago, a ham on 75m did that. Afterwards, as W8JI (who also was present) said, "He was just 'killing people'", meaning that his QSO count immediately went way up. His ...

4

Here are the fields for AM_conductivity_m3.seq_.txt and AM_conductivity_m3hw.seq_.txt files: 4001 21.5750 158.2760 21.5840 158.1900 2.00 5000.00 Fields, left to right: The number of the line segment. The north latitude of the start of the segment. The west longitude of the start of the segment. The north latitude of the end of the segment. The ...

3

With only three radials, the wire you use is probably not very relevant. Although a smaller wire has a higher resistance and thus loss, with only three radials directly on the ground your losses will still be dominated by the resistive loss of the soil. As a rule of thumb, a good ground requires at least 16 radials. It's not critical that they be exactly a ...

3

AM broadcast stations do not use the Earth as ground for the antenna. To the contrary, they go through great expense laying huge radial fields precisely to avoid ground currents in the Earth. See these pictures of WTMJ on qsl.net. Here's one of them: If you look closely, there is a copper mesh all around the antenna base. Around the base perimeter, there is ...

3

Well, I operate daily from an old copper mine - where the main mineral is iron! The comment about iron oxide are not correct. In places such as here, and where the OP mentions, the ground is highly acidic. Consequently, iron is in the FE2+ (ferric) state, not the FE3+ (ferrous/rust) state. This may or may not affect conductivity. You will have to ...

3

Probably not much effect from iron in the ground. HF communications are very sensitive to the ionosphere and other natural effects. Predictions are difficult, and only give a probability, never a guarantee. Real data are thin on the ground, and you know that the plural of anecdote is not data. HF propagation happens mostly in the air, and by reflection off ...

2

I did find a reference in MCRP 6-22D, Marine Corp Antenna Handbook page 1-10. It talks specifically to ground wave. “At high frequencies, 3 to 30 MHz, the ground’s conductivity is extremely important, especially above 10 MHz where the dielectric constant or conductivity of the Earth’s surface determines how much signal absorption occurs. In general, the ...

2

2

Can you elevate the radials? Two or three properly installed elevated radials can be just as effective as 120 on the ground! By properly installed, I mean that they should be roughly 10 feet high and have an effective common-mode choke on the coax right at the junction of the radials and coax shield. This junction MUST NOT BE GROUNDED. Try and make the ...

2

Below is the result of a NEC4.2 comparison of a 75m, center-fed dipole at 10m elevation above 15 mS/m Earth, with and without a reflector on the surface of the earth directly under it. The gain improvement with the reflector is about 0.03 dB. As for adding a single wire on the surface of the earth or buried several inches below the surface to improve the ...

2

Random long wires - probably will help. Especially if they're aligned with the dipole above them. Space blankets might not have a thick enough metal layer to be effective at HF, (though I know reflective window film is as good as wire mesh at 900 MHz). Most importantly, things < ${1\over2}\lambda$, not connected together, will make no difference, the ...

1

The figures on that map are approximate. They represent estimated ground conductivity in millimhos per meter. And it varies with (among other things) how wet or dry the soil is. I live near a line where on one side it is 15, and on the other side it is 8. Driving across that line, the conductivity does not suddenly jump to the other number. Rather, it ...

1

You could get the data from e.g. the Sentinel-1 or possible the TerraSAR-X satellite missions, and look for the ground characteristics (much like for moisture estimation) that are beneficial to ground wave propagation. Don't know how much that actually helps – C-Band wave propagation is pretty different to HF, but I could imagine that conductivity estimates ...

1

Either elevated radials, or radials lying on the ground or buried just below the surface can work just fine. The difference usually comes down to what's more convenient to install. I would not recommend a folded counterpoise, or any other kind of counterpoise which is not simply a straight wire unless you are constrained by space. Elevated radials have the ...

1

Be aware that connecting your antenna to a good solid earth, and then connecting your radio gear to that antenna, and to the mains electricity supply can be a hazard in the event of a mains electrical fault. Some properties in some parts of the world are wired using a 'protective multiple earth' (PME) system, and bringing a 'real' earth into the shack can ...

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