Opweb.de

When used with a highly sensitive radio set the kit should be located at least three and preferably five feet away. If used with a less sensitive receiver it may be found, on trial, that a smaller distance will be satisfactory. On the other hand, a much greater separation is not desirable. The attachment plug and cord, extended if necessary, should be run to a lighting receptacle or wall outlet and should be kept as far as practicable from all wires leading to the radio set, including antenna and ground. Tiwo or three wires for carrying the “B” battery potentials to the set may be run in the usual manner. The output from the radio receiver should be carried to the input terminals of the kit by a double telephone cord or a pair of twisted leads which should be kept separate from the “B” battery leads. A similar conductor should be used connecting the loudspeaker to the output terminals. Under certain conditions better quality can be obtained merely by interchanging the input leads at the input terminal posts. The majority of radio sets have the positive or negative filament terminal connected to ground. This provides a sufficient grounding for the eliminator. With sets wherein the filaments are not grounded and those employing an ungrounded loop, it may be advisable to ground them through a condenser of from two to four M. P. capacity. This ground is unnecessary in many cases but under certain conditions it is desirable to reduce the alternating current hum. If the kit is used merely as a power Amplifier it may be desirable to ground the B— terminal. A word of caution should be added here concerning the attempt to measure the voltage at the “B” battery terminals of the kit. The ordinary, inexpensive, voltmeter draws so much current that the increased load on the kit lowers the voltage considerably so that the readings of such a meter are meaningless unless the meter load is known and taken into account. Reliable results may be obtained by using a five milli- ampere meter connected in series with a resistance of 100,000 ohms. Such a voltmeter draws only one milliampere per 100 volts deflection, which is permissible. Tests have shown that, on the average, using the type HB Raytheon and with the UX-171 tube in the circuit, the open circuit voltage at the —(—90 terminal is about 145. This potential drops at a rate of 3.25 volts per milliampere of current drawn from this terminal. The open circuit voltage at the —(—40 volt terminal is about 50 and this diminishes at a rate of 2.23 volts per milliampere load from this terminal. These values meet the requirements of the great majority of radio receivers. It is possible to use either a UX-112 or a UX-210 tube for the power Amplifier, but for the best quality of reproduction the UX-171 tube is recommended.