Hints on Design and Installation of Automobile Radio
September 1932 Radio News Article

September 1932 Radio News [Table of Contents] Wax nostalgic about and learn from the history of early electronics. See articles from Radio & Television News, published 1919-1959. All copyrights hereby acknowledged.

Having never owned a diesel-powered car or truck, I can't say whether not having a high tension (voltage) ignition system eliminates any possible interference with AM radio reception. Although not many people listen to AM radio these days, there was a time when it was still a popular option along with FM, and a time before that when it was the only option. Diesels have long been much more prevalent in Europe, so those of you who were around in the era might recall whether you were contently listening to the BBC in static-free bliss while your petrol-powered friends were fighting the ignition noise battle with chokes, capacitors, and resistor wires. Ignition noise did not come only from the car you were driving; often in high density city environments the interference from nearby cars, trucks, and buses could render acceptable radio reception impossible no matter how great the noise mitigation in your own vehicle was.

Hints on Design and Installation of Automobile Radio

The rather complex electrical system of the modern automobile offers many problems for the auto radio installation man. The following pointers on noise elimination, based on the author's extensive experience in this field, should prove unusually helpful.

Part Two
By M. J. Sheedy

In making a radio installation in an automobile it is always well to look over the car wiring and make certain it is in good order, also that the breaker points are clean and have a flat surface, and that the generator brushes and commutator are in good condition.

Shielding the spark plug wires is not recommended. It is expensive and the results obtained do not warrant it. Tight shielding adds considerable capacity to the system. This capacity must be charged and consequently absorbs energy from the coil. This will be noticeable by hard starting. In cars equipped with a magneto this rule does not apply.

Shielding H. T. Wiring

Rubber covered high tension wires should never be shielded as corona trouble and leakage will soon be experienced if tight shielding is used. Where it is necessary to shield a high tension wire, varnished cambric covered wire should be used. This wire can also be had with metal shielding already on it.

If the ignition coil or coils are mounted on the car side of the dash, they should be removed and remounted under the hood. Always keep the hood down when listening for spark noise in a receiver. The hood acts as a shield to confine the radiation. If a top antenna is used, it is a good idea to bypass the wire to the dome and tonneau lights. This will be necessary if the switch is on the ground side. Another wrinkle is to lengthen the distributor rotor, so as to shorten the gap.

Quite often a noisy condition can be traced to poor suppressors. While a collection of suppressors of various makes, when tested, may show a nearly uniformed d.c. resistance, yet their a.c. resistance may vary greatly. This is caused by either the quality or nature of the material, or the kind of binder used in it's composition. The simplest and best way to test them is to notice the color of the spark. The whiter the spark the more efficient the suppressor. The more blue in the spark, the more a.c. there is present.

If a motor does not idle properly with suppressors, it may often be remedied by shortening the gap in the spark plugs. The effect of the suppressor on the plugs is like increased compression.

The installation and service of auto radio equipment can be most efficiently handled by automotive electric shops, with the services of a good radio man. Large service stations of this type, having drive-in facilities, can supply service for a number of dealers, and are also in a position to make direct sales to their car service customers. Customers sent in for radio work are also good prospects for car service work.

Very few dealers have the facilities to properly do the work and frequently work an injustice on the customer when they try it. Curb-stone installations are rarely satisfactory. A few manufacturers discourage their dealers from attempting it by only guaranteeing the equipment when it is installed by an authorized service station.

This policy reacts to the dealer's advantage. It relieves him of the installation problem, and assures the customer of specialized and intelligent service and gives the dealer greater confidence to make sales. Poor installations have spoiled more sales than poor receivers.

Every radio dealer, car dealer, and automotive service station can sell auto radios. It is an excellent sales item for the radio dealer in the spring and summer months, when the sale of household receivers is slow.

Auto radio is gradually taking a prominent place in the radio industry. Practically all the leading manufacturers are now marketing receivers for this purpose. Although auto radio was originally introduced for pleasure cars, it's field is rapidly expanding, and there are unlimited opportunities for this business.

The thousands of buses in use throughout the country in themselves constitute a sizable market. Anyone who has ridden any distance by bus, can appreciate this. A little entertainment or current news flashes go a long way to break the monotony of an otherwise tedious ride. Very little effort has been made, however, to sell this market. We will admit that the general run of equipment has not been up to standard for this type of service. With the introduction of superhetrodyne receivers, special tubes, greater output with less current drain, and dynomotors for plate current supply, this business can now be gone after with greater confidence. Buses equipped with radio are given preference by the public and are also in demand (or private charter.

Taxicabs constitute another prospective market. Such installations can be arranged so that the set can only be used when a fare is in the car. Much more headway has been made in Europe along this line than in this country.

If a radio is appropriate in an automobile, it certainly is at home in a motor boat. Household receivers are not adaptable to this use and do not give consistent service when used aboard ship. Automobile receivers are better able to stand the rigors of this type of service. The one drawback is that while present-day radios are fine for speed boats, and runabouts, they are not quite adaptable for the small cruisers, due to the mounting arrangements and types of control used. The small cruiser constitutes the greatest market.

Motor-Boat Radio

There is an opportunity for some enterprising manufacturer to market a set to fill this need. Such receivers should be similar in type to the present-day midgets, but built to withstand the corrosive effects of salt air and dampness. Provision should also be made for additional speakers. Motorboat builders and dealers are waiting for such a receiver. The radio mariner in coastal waters can set up a loop antenna with such a receiver and have an excellent direction finder.

Auto radio has made more progress from an engineering standpoint in the last eighteen months, than in the previous three years of its history. This is largely due to the cooperation of the accessory manufacturers in designing special tubes, batteries, generators, condensers, etc.

In selling or installing radio sets in cars or boats one should not overlook the advantages offered by the auto B eliminators, a number of which have been placed on the market within the past few months. Equipped with one of these units, the auto radio is as trouble free as the home receiver. The A battery, of course, requires no special attention so far as radio is concerned, as that is of necessity kept in proper operating condition at all times anyway. The extra drain imposed on it by the radio is slight, but even this can be compensated for by increasing the charging rate at the car generator. The use of a B eliminator, depending on the car storage battery for its supply source, not only eliminates the B battery replacement nuisance, but most of these eliminators require less than half the space required for B batteries of the same total voltage. One can be mounted in any spare space in or beneath the car.

In this connection it is well to make sure before buying any particular make of eliminator, that it will work with the receiver which is to be used. Tests have shown that some of the eliminators on the market are noisy with certain receivers but quite satisfactory with others. Other eliminators, on the other hand, work satisfactorily, with any receiver. Some auto receiver manufacturers have tested various eliminators and are therefore in a position to recommend the most satisfactory eliminators for use with their equipment. On the whole, there is now some excellent auto radio equipment on the market and it is worth looking into. What was yesterday's luxury is fast becom­ing tomorrow's necessity.

Posted July 9, 2014