Archive for the ‘Communications’ Category
February 11th, 2012 | 
Author: It’s probably not something many people are interested in unless they’re some kind of an electrical engineer or just bored, but understanding how an antenna works can be useful when the one on your TV or radio goes south on you and the reason is beyond your comprehension.
Trying to explain how an antenna works in simple English is not an easy task as there are a lot of technical specifications that need to be explained. But a general understanding is possible without getting into tech speak that would make Einstein cringe.
In order for an antenna to work it has to radiate. Your antenna, whether TV or radio has what is called free electrons running through it. It is these free electrons that vibrate. The question becomes, how do these free electrons vibrate and what causes them to vibrate?
Well, in real life it takes an electric field to move an electron. If you take an isolated straight dipole, the power comes from the combined fields of all the charged particles, both positive and negative, in the antenna. We’ll call this field the antenna’s coulomb field.
In addition to this field, the antenna exhibits a magnetic field that is the sum of the magnetic fields of all the free moving electrons. The antenna also has a dynamic electric field that is the vector sum of the dynamic electric fields of all the free electrons. What we can do is separate the electric field of the antenna at any point in space into two components. One of the components will be in phase with the total magnetic field and the other will be 90 degrees out of phase. The in-phase component is the radiation field of the antenna and the out of phase component is the induction field. At the antenna, both fields are parallel to the metal surface.
Read the rest of this entry »
Posted in 
Tags: 
Continuing with our research into the CB craze of the mid 70s we’ll take a look at what were considered the elite antennas when it came to having a CB setup. While the truckers may have ruled the roads and channel 19, it was the everyday hobbyist who ruled the airwaves from his home, and rule they did.
If you were on CB and really wanted to impress people with your booming voice over the airwaves you had no choice but to set up a base unit. Not only were the units themselves powerful but the antennas that people put up on their roof tops could have given some rival TV stations a run for their money.
Choosing a CB antenna for your base station was not easy. There were plenty to choose from and they all had their pluses and minuses.
One of the most powerful, yet most frustrating was the ever popular Moon Raker. This was a beam antenna that looked very similar to TV antennas, most having 3 elements mounted on an 11 meter base. These were called regular Moon Rakers. However, there were beam antennas that had up to six elements on them. They were referred to as a Moon Raker 6. These things were huge. The problem with them was that they were directional antennas. What this means is that depending on what direction your antenna was pointing that was where you got your best reception and transmission. So if you were speaking to somebody who was south of you and your antenna was pointing north you had to turn the antenna 180 degrees in order to get a decent reception. This got to be a pain after a while. The plus side was that these antennas were so powerful they could cut through anything once you had your target zeroed in.
Read the rest of this entry »
An anonymous proxy, also referred to as an anonymous proxy server, allows a client to access a file, web page, or some other resources through a server which services the requests of the client through another remote server. For example, when a client accesses a web page through an anonymous proxy, the client talks to the proxy and the proxy talks to the web page, maintaining the privacy of the client, such as his/her IP address. The purpose of such a proxy, or a server, is to protect the privacy of the client from the service and from other individuals who may be logging and inspecting the client’s connection.
Such proxies are commonly used in schools and workspaces, to pass-by potential firewalls and monitoring services in place. Students will often utilize anonymous proxies to access social networking websites deemed and blocked by the school as harming the productivity of the students. Employees of a company may try to circumvent forms of monitoring within a company that may try to track or control which websites its employees are visiting.
Read the rest of this entry »
In today’s world, communications are of utmost importance, there is absolutely no doubt about that. Satellite tv is one of the technological breakthroughs of the 20th century. Made possible because of the massive satellite fleets deployed by different companies and with different purposes, satellite tv has in a way revolutionized communications.
The communications satellites of different companies relay on an increasingly diverse range of TV programming. And when it comes to the options you have for your satellite tv receiver, this will greatly depend on the very nature of the satellite tv service you desire to view. There are satellite tv programs which are (FTA). FTA is an abbreviation from “free to air”. However, there are other satellite tv services which are encrypted, and are only available to subscribers of various satellite tv companies.
Another important distinction must also be made between satellite tv services which are analog and those which are digital. The analog services are based on electromagnetic waves that vary in their frequency. I am sure you have heard of the term FM, which is short for frequency modulation. Also, analogue transmissions can vary in intensity. In the latter case, the process is called amplitude modulation, or AM.
Read the rest of this entry »
