WIRELESS NEWS.
STATIC ELIMINATION. A NOVEL METHOD.
(specially written for “The Press.”)
(By “Electra.”)
From the Christchurch Press, Volume LXI, Issue 18533, 7 November 1925, Page 6.
One of the greatest problems of present-day radio reception is static, which is sometimes known as atmospherics. Since wireless communication was first put into practice engineers hare striven and tried all possible methods and means to overcome this obstacle.
Interference from static is one of the greatest difficulties encountered in radio communication. Although this form of interference has been greatly reduced by means of special antennae, it is of no practical value to the radio broadcast fan. The reason is obvious. The antennae system used for this purpose is seven miles in length. Other systems of balancing have been tried with somewhat successful results. But in no case has it been possible to reduce static, interference to zero. These somewhat complicated systems merely reduce the static ratio to a value less than the signal strength of the incoming signal.
Most systems will not operate on the reception of radio broadcast signals, and therefore have been applied only to long wave trans-Atlantic wireless communication.
Apparently static has no given wavelength. That is, it may be heard on all wave-lengths simultaneously. For this reason it would be impossible to do away with this peculiar form of interference by means of some tuning device.
It was recently announced, however, that, the problem of static was believed to have been overcome by the discovery of two Chicago amateurs. The radio transmitting station emits two types of waves, according to theory. One is known as the “space wave,” which is radiated, from the antennae at an angle, and travels in space until it strikes a. layer which it, cannot penetrate. This is sometimes called the “heavy side layer.” It is then refracted back to the earth.
The Earth-bound Wave.
The other type of wave radiated by the transmitting station is known as the “earth-bound” wave, and travels along the surface of the earth. It is this latter wave that the Chicago amateurs employ in their anti-static device. The inventors are James D. and Ray Gibson, father and son respectively. The father has been a telegraph operator for many years, while his son first became interested in the radio art during the world war.
This device consists of a piece of specially prepared lead-sheathed wire 60ft in” length, and divided into condensers, together with two pick-ups, one attached to the centre of the cable and the other at the ground end. The wire is buried in the ground for a distance of 50ft at a depth of 18in to two feet, The remaining part of the wire is used for lead-in to the receiver. There apparently is not any restriction on the length of the lead-in from the ground to the set.
Mr Gibson and his son have placed their device before experts, who gave it a test for five months. It is claimed by the inventors that these “earthbound” waves are free from static and that other weather conditions do not affect them.
Broadcasting.
The orders for the first two Western Electric Broadcasting Stations have been accepted by the manufacturers, and the plants are expected to arrive in Auckland and Christchurch in February next.
It is stated that the apparatus to be supplied, although high in first cost, is the outcome of experience in more than 40 of the best known broadcasting stations overseas, and is considered the most modern and efficient radio broadcasting equipment in the world to-day. Improved speech circuits, the reduction of harmonics, a quieter carrier wave, and better facilities for monitorial and control make it capable of higher quality transmission. The plant is designed.to deliver 500 watts of radio frequency power to the aerial system, which will give a 17 mile daylight range on a crystal set, and the electrical power required is approximately, plate potential 1600 volts, total plate current, .9 amperes, filament potential 14.3 volts, total filament current 29.31 amperes.
The station at Auckland will be installed on Messrs Geo. Court and Sons’ big new building in Karangahape road The aerial will consist of two lattice steel towers spanning 220 feet and over 100 feet above the roof, which is in turn 80 feet above the street The operating room, also situated on the roof, and directly under the aerial, will measure 20 feet by 30 feet”. Plans are now in hand for building a special studio with efficient acoustic properties so as to obtain the maximum effect from the first-class talent it is the intention of the company to broadcast. Similar arrangements are in hand for Christchurch, and it is expected that both the new stations will commence broadcasting within a few weeks of each other. Wellington and Dunedin conditions are also being investigated with a view to proceeding with the installation of stations immediately the Auckland and Christchurch plants are in operation. Now that the matter of delivery of the very latest and most modern broadcasting equipment has been finalised, the company will concentrate on providing the best and latest in studio accommodation and when that is more advanced the company will turn its attention to the programmes to be broadcast.
The proposals for Dominion broad-casting have been submitted to one of the most prominent authorities in the World and mailed information just received from England gives the information that after examination of these proposals, it is considered that the scheme as defined by the Government is the best solution to the problems of national broadcasting in New Zealand, in fact, no alternative proposition to that submitted was required.
Friction, spring or pressure contacts between the movable and stationary parts of tuning instruments are a frequent source of noise and trouble. The connexion may seem excellent-when the new condenser or variometer is inspected in the shop, but after a period of use we begin to notice scratching and rasping noises upon turning the dials, which, are due to loose or corroded contacts resulting from the inevitable wear and tear, oxidation, etc. There are enough unavoidable noises about any radio without permitting such as these to continue, especially since they represent a decided lowering of efficiency through high resistance and the possible loss of DX.
Substituting short lengths of flexible wire, commonly called pigtails, for these movable contacts is to be highly recommended as well worth the trouble. To be flexible the wire must be strained the finer the strands the more so. Braided wire is especially satisfactory. The wire may or may not be insulated; it need not be unless two leads are to be brought out very close to each other, which is generally poor practice. The two ends must be soldered, of course. It is essential that the solder penetrate the strands thoroughly to make a good joint. The usual precautions of absolute cleanliness, a hot and well-tinned iron, and a minimum of some good non-corrosive flux apply here. This gives us a perfect electrical contact but some mechanical considerations are also necessary.
It is obvious that the pigtails are liable to be twisted off their anchorages if the motor be moved too far. To prevent this we should limit the motion of the dial to not more than one complete revolution; a half revolution or 180 degrees, is just as satisfactory and often simpler to obtain. This can be done in several ways. While it is possible to rely on one’s memory and simply form the habit of never going beyond the numbered portion of the dial, it is not the safest way, especially in the average family.
