Dead air

This article is about the technical phenomenon, for the Iain Banks novel see Dead Air.

Dead air is a phenomenon whereby a broadcast which normally carries audio or video unintentionally becomes silent or blank (also known as unmodulated carrier). The term is most often used in cases where programmed material comes to an unexpected halt, either through operator error or for technical reasons, although it is also used in cases where a broadcaster has 'dried up'. It is the duty of all concerned to rectify the problem as quickly as possible; in many parts of the world dead air is considered to be one of the worst crimes a broadcaster can commit.

This is different from being off-the-air. When a station is off the air, the transmitter is not active and there is no signal at all. Dead air is where a carrier signal is being transmitted, but there is no modulation of that signal.

In the United Kingdom, any radio station which transmits dead air for more than ten minutes without rectifying the situation, broadcasting an announcement, or otherwise warning its listeners, can be penalised and may be fined up to £25,000 per minute by the independent regulator and competition authority for UK communications industries, Ofcom.

Dead air can also apply to television broadcasting, generally when a television channel has an interruption to its output, resulting in a blank screen or in the case of digital television, a frozen image, until output is restored or an apology message is broadcast.

Having dead air during commercials or sponsorship announcements can cost networks considerable advertising revenue.

Examples

An example of dead air was a Chris Evans radio transmission for the British Virgin Radio station. As a promotional stunt, Evans did not arrive for work, and his show went to air carrying nothing for about twenty five minutes.

Another case was BBC Radio 4's failure to broadcast Big Ben's midnight chimes on New Year's Day 2003; after announcing the chimes, a technical error caused the station to fall silent for a minute. This was caused by the correct feed not being faded up. Ironically, the chimes were supposed to be coming via a new link which the BBC had just installed to Westminster just to avoid cases of dead air.

On September 11, 1987, Dan Rather walked off the set of the CBS Evening News when a late running U.S. Open tennis match threatened to delay the start of his news broadcast. The match then ended sooner than expected but Rather was gone. The network broadcast six minutes of dead air before Rather was found and returned to the studio. There was considerable criticism of Rather for the incident.

Batteryless radio

A Baygen clockwork radio with crank in winding position

Radio receivers were originally operated by battery. The term batteryless radio was initially used for the radio receivers which could be used directly by AC mains supply (mains radio).

It was invented by Edward S. Rogers, Sr. on April 8, 1925 in Canada who made world history when he and his two chief engineers built the world’s first all-electric radio. The unit operated with 5 Rogers AC Vacuum tube and the Rogers Battery-Eliminator Power Unit (power supply). This unit later becomes marketed for $120 [1] as "Type 120". Batteryless Radio were not introduced in the United States until May, 1926 and then in Europe in 1927.[2]

Crystal radio receivers are a very simple kind of batteryless radio receiver. They do not need a battery or power source, except for the power that they receive from radio waves using their long outdoor wire antenna.

Thermoelectricity was widely used in the remote parts of the Soviet Union from the 1920s to power radios. The equipment comprised some bi-metal rods, one end of which could be inserted into the fireplace to get hot with the other end left out in the cold.

After second world war, kerosene radios were made in Moscow for use in rural areas. These all-wave radios were powered by the kerosene lamp hanging above it. A group of thermocouples was heated internally to 570 degrees by the flame. Fins cool the outside to about 90 degrees. The temperature differential generates enough current to operate the low-drain receiver.[3]

Foot operated radio or Pedal radio were once used in Australia. Another way of achieving the same function is Clockwork radio, hand crank radio and solar radio [4].

A modern crystal radio set

SWR Meter

Equipment for Radio Technician, but if you install HF Codan it's not need.
Because in HF-SSB Codan is include at Handle Mic.

The Bird Model 43 THRULINE® directional wattmeter is a portable insertion-type instrument for measuring forward and reflected power in coaxial transmission lines. It will accurately measure RF power under any load condition. Plug-in elements are available to fit your frequency and power needs. The more common ones are listed below.

The Bird Model 43 N is shown left with optional elements (sometimes called slugs). This model features N connectors for input and output.

The plug-in elements (slugs) determine the power rating and frequency range of the Bird 43 wattmeter. A few of the more common ones are listed below.