AUTOMOBILE RECEPTION.

Manawatu Times, Volume 62, Issue 37, 13 February 1937, Page 15 (Supplement)

AUTOMOBILE RECEPTION.

The quality of reception from, an .utomobile radio set depends, to a great extent, on the way in which the installation work is done. And since the same make and model of automobile will sometimes respond differently to the installation methods used, the problem of the mechanic is indeed a difficult one.

There are three general types of disturbances which must be eliminated in making the installation of an automobile radio. The first of these, called chassis pick-up, is the noise that is transmitted to the loud speaker through faulty mechanical installation of the set. Poor ground connections at the chassis mounting studs, loose wire connections, poor ground connections at condensers and loose wires in the distributor cap or a partially discharged battery are responsible for the majority of this class of noise. The battery ucts as a large electrolytic condenser, and When it becomes run down it loses its power to by-pass noises generated by the engine and the generator. Chassis pick-up noises are audible in the set with the radio antenna disconnected, and when attempting to eliminate the noises from any radio, it is advisable to first disconnect the antenna lead-in and classify the noise. Chassis pick-up noises should be eliminated first.

The second group of noises is classed as antenna pick-up, and consists of ignition interference picked up by the rnteuia. lead-in, and is most noticeable when the aerial is connected to the speaker. Good condensers with good grounds, clean and properly spaced •park plugs, clean and properly spaced breaker points, clean and tight connections at ground straps, with shielding and bonding at all points likely to transmit ignition interference to the loud speaker will usually take care of tlris class of disturbance.

The third group is classed as the static discharge group, and consists of static given off by .wheels and tires, and by the road surface. It is easy to eliminate this class of interference, as it will occur only when the car is in motion, and with the engine turned off. St&tie eliminators installed in the front and rear wheels, transmission ground straps, grounds installed on torque tubes and on muffler tail pipes have to be resorted to. Tire inflation also enters into the picture, as under-inflated tires cover more Toad surface end therefore increase tires static.

Most of the present-day automobile rqdie sets do not require supporters on ihe spark plugs, and employ a suppressor only on the distributor high tension wire. Spark plug suppressors should be avoided if possible, as they •re inclined to interfere with engine performance. Low tension distributor wires that travel to the distributor parallel with the high tension wire sometimes have to be shielded to prevent breaker point interference. Spark plug and distributor wires that are carried in metal tubes present a source of trouble for the radio, and best results have been obtained when the wires have been removed from the tube, and if necessary shielded individually. If the coil is located on the instrument panel, the high tension wire should be shielded for a distance of from about iin. from the coil to the front side of the dash panel, with the shielding soldered to the front side of the dash. The principal point to remember throughout the installation of the set. is to be sure that wherever a connection is made the paint and dirt is scraped off so that a bright metal surface is available. It is tne general practice to install a condenser on the generator, connecting the lead to the output terminal. Care should be exercised to be sure that the terminal is not connected to the field terminal of the generator; such an installation would interfere with the voltage control unit. Many of the current model cars use a condenser connected to the negative side of the ammeter, and some connect a small condenser in the dome light wire. Car accessories sometimes interfere with radio reception, causing a hum, and in those cases small condensers have to be installed. Thcro are certain points that require special bonding on the various models experience having shown that these additional connections are necesary to satisfactory radio reception. The 1930 Oldsmobile should have a ground strap installed from the left rear cylinder head bolt to the top of the starting pedal bracket, and another ground strap from the frame “X" member to the rear of the transmission. The metal pipes and Cables that pass through the dash panel should be bonded to the front side of the dash. The steering column should also be bonded to the dash, and a ground strap installed from the muffler flange to the frame side. rail. Pontiac requires bonding of the pipes and cables leading through the dash panel, and also a ground from the torque tube to the frame cross member just to the rear of the tunnel in the * * KY V member. The end pigtail of the antenna lead-in shield should be grounded to the left front antenna bracket. It is important that the paint be scraped off the bracket at the joint and also at the junction between the bracket and the running board. A condenser is mounted on the Ford roil, the lead being connected to the low tension terminal on the left rear aide of the coil. The generator condenser is attached to the generator cut-out mounting lug, with the lead connected to the battery terminal of the cut-out. An additional condenser is provided to removed interference from the dome light wire, and is mounted to the screw connecting the instrument panel to the pillar, the lead being connected to the bullet connector ou the dome light wire at the entrance to the pillar. The elec-' trie oil and gas gauges also require con-

d«nsers, the oil gauge condenser being mounted on the transmission housing underneath the starter wire clamp, with the lead collected to the terminal of the gaugo on the flywheel housing. The gas gaugo condenser is installed on top of the left side of the gas tank. Nash Model 400 and the Lafayette for 1936 use a condenser on tho generator and on the dome light wire, and in addition, it is suggested that the distributor rotor terminal be peened bc that it comes within about O.OOlin. ot the stationary electrodes of the distributor cap. The Ambassador models also use a condenser on the ammeter side of the ignition coil. Chrysler, Do Soto, Dodge and Plymouth models follow tho same general points outlined above, bonding the pipes and cables leading through the dash panel, installing a ground on the steering column and using condensers on tho generator, dome light wire and ammeter