7

One of my favorite lightning anecdotes is this story by W8JI. He had lightning strike a tree, blowing the bark off down the trunk, and making a huge hole in the ground. And then some 20 feet away, the current arced to a Beverage antenna and traveled the length of the antenna to get to the ground on the other side of the antenna. The reason for this is soil ...


7

Depends on how you want to look at it. Two ground rods spaced close together will be less effective than two rods with sufficient spacing, but still at least as effective as just one rod. So it's not like adding the additional rod will make things worse, but it won't add as much as it could have. The reason for this: the real earth isn't a perfect conductor (...


6

The picture you have drawn suggests a lightning suppressor installed in this way will do little to nothing to protect your station. The suppressor does only one thing: it limits the maximum voltage between the center conductor and the shield. It doesn't do anything to limit strike current on the shield, which is where most of the energy is anyhow. The ...


5

The purpose of the ground radials isn’t to ground the counterpoise. The purpose of a dense field of radials is to emulate as much as possible a perfect mirror surface, so that, to the far field, the vertical monopole seems to have a mirror image half that makes the monopole seem more like a full size vertical dipole, with a pattern maxima orthogonal to the ...


5

Another way to detect current on the outside of coax is to run your hand up and down the coax wile an analyzer is connected , if you see a fluctuation on the meter then current is following on the outside. On vhf I built sleeve chokes to remove it with great results. KC5ULU


5

There are some suitable connections in the reusable Cadweld product line: But you're right, there don't appear to be any similar connections in the One Shot line. An alternative is brazing. An alloy like Harris Stay-Silv 15 works well. I've managed to make acceptable connections (barely) with a good MAP plumbing torch to ground rods that are not buried yet ...


4

The reason to avoid multiple of a quarter-wavelength is that by virtue of the length this will transform the low impedance at the ground rod into a high impedance. This implies you are expecting this ground connection to carry significant RF current when you transmit. Such antenna system designs are not usually good ones, for a couple reasons. Firstly, soil ...


4

Your two ground conductors must be connected at both ends. They must be connected at the bottom because that's where the ground is and they aren't ground conductors if they aren't connected there. And they must be connected at the top because if they are not, you don't have a single point ground. Without a single point ground the potentials between the two ...


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

If the schematic doesn't show a separate audio signal ground, then the audio input ground is clearly meant to be connected to chassis ground. The power supply ground is also not shown, which means that it too should be tied to chassis ground. All the ground symbols in the schematic are chassis ground, rather than earth ground. Since the circuit is an RF ...


3

The information below is extracted from the "benchmark" 1937 I.R.E. paper* of Brown, Lewis & Epstein of RCA Laboratories, and is based on their accurately measured data for these systems. IMO, the outlined and underlined text at the bottom of this clip is worth remembering, and deserves greater access/acceptance. *Proceedings of the Institute of Radio ...


3

Below for some perspective on this topic is a NEC4.2 analysis showing the difference in performance of a 40m, 1/4-wavelength, unloaded, base-fed vertical monopole antenna system when driven against either a 5/8" OD or a 12" OD, copper-clad, 8-ft long ground rod buried in poor Earth (1 mS/m, d.c. 5). Increasing the ground rod OD up to 12" is ...


3

A dipole antenna does not require a connection to an "r-f ground" reference, either in the form of a ground rod or a set of buried radials. Its radiation efficiency typically is ~95% or more without it. OTOH, a vertical monopole does require a path to an r-f ground reference, because that path provides the 2nd terminal of the antenna system, which ...


3

TLDR: 60 volts AC divided by the transformer CMRR is much greater than 1 mA times the resistance of the wire installed. -- In the first case - the raspberry Pi was floating at 60 V AC above ground, being powered by a two-pin USB adapter. The radio was earthed by its power supply, coax, etc. So the transformers have 60 volts across them, and even the ...


2

If at all possible, the feed line should go through a panel that is connected by a short cable, or directly connected, to a ground rod. A lightning arrester is a good idea also. All earth grounds should be connected, including the ground rod connected to the service panel, the ground rod connected to the coax shield, and your station ground. In the US, ...


2

Surely a 1m copper stake provides better ground connectivity for a vertical dipole? What really matters is conductivity. Current doesn't just go in the ground rod and then it's done. It has to flow through the surrounding soil. Soil isn't a very good conductor: (68.2 kΩ, says the display) Now imagine how much lower this resistance would be with a copper ...


2

Because the radials act as ground, and they're better at it than actual ground. Ground (as in: dirt) isn't a great conductor. A couple laid out good conductors hence work much better as ground plane than well-connected earth. For RF, a good connection to ground potential isn't necessary – what's necessary is that there's a large plane that conducts.


2

One important reason is safety. One wants the exposed metal part of the coax connector to be at the same potential as the Transmitter case at one end, and any grounded equipment at the other end. Not at a high (RF or A/C) voltage.


2

The coax shield must be at ground potential if you want the coax to function as a non-radiating transmission line. If the shield isn't at ground potential, then there will be a non-zero electromagnetic field between the coax and its surroundings. Meaning, it will radiate. The shield could be left floating, but the shield can be grounded without changing the ...


1

Assuming that the copper earth/ground rod is buried in earth, it is tightly coupled to the earth. Because of the tight coupling to a lossy material, there will be no resonance effects at the end. In other words, the length of the earth/ground rod doesn't matter for resonance purposes, as long as it's buried. Your connection to earth must be short, a small ...


1

A part of the antenna system (system = antenna + transmission line) that is truly grounded can't radiate. Most antenna systems are more efficient when the antenna, the part that is designed to radiate, is up high. So the antenna is deliberately ungrounded. Antennas are usually designed with the assumption that the transmission line doesn't radiate much; ...


1

Just about anything should do. The ground connection between the entrance panel and the desk shouldn't carry any current if everything else is properly installed. I'd probably use some tinned copper braid because I already have some and it would be easy to install. It's not too important what's connecting the desk and that exterior panel because: it shouldn'...


1

Ground wire is very inductive and thus high impedance to sub-nanosecond arc rise time when the leader path finally conducts. Therefore you want the shortest path to the air gap arc suppressor which is sub-picofarad higher impedance then the current will have a greater chance of following the ground wire. The voltage induced may still be high but hopefully ...


1

As Phil Frost mentioned, you can try the MAPP gas and silver brazing rods. There is a good article which has some suggestions on doing all this, including how to get the materials on a budget (scrap copper roof flashing, for example, instead of expensive strapping). Lowes has a MAPP gas cylinder and torch for about $55. See this article for details. It ...


1

If by improving conductivity, you mean flooding several acres or square miles with ocean (or saltier) sea water (or via natural intrusion near a low lying shoreline or wetlands), or installing a solid copper floor several square wavelengths in size in the parking lot, yes. But some people have reported improved antenna performance by putting a metal mesh of ...


1

A rather common expectation is that bonding the outer surface of the shield of a coaxial cable to a buried ground rod effectively "grounds" that conducting surface at radio frequencies. If that was true, then it would be a good means of removing common-mode currents that can be present in some typical antenna/transmit systems. The study below is ...


1

RE (from the OP): I'm confused by having one-half of the dipole tied to the RF transmitter output and to Earth ground. Can anyone explain the electronics behind what is going on? Just to note that all antenna systems are two-terminal devices — no r-f energy will flow on one "leg" of a dipole without an equal amount of r-f energy flowing on the other leg. ...


1

Welcome to the world of RF (radio frequency) and AC power, where the obvious rules of DC power don't work. In RF electronics, just because two wires are DC shorted doesn't mean they are RF shorted. In RF, a transmission line (like coax) can be shorted at one end and measure as RF open at the other end if it is an odd multiple of quarter wavelengths ...


1

This handy item at least makes the disconection easier: https://wr9r.com/product/antenna-disconnect/


1

Lightning takes the path of least resistance I believe. If you have a larger conductor just above the highest point of your antenna going to ground that is a better conductor than your antenna I would think that would cover you.


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