The Birmingham age-herald., 1922-05-28
WEIRD NOISES IN RADIO RECEIVER
 ARE UNNECESSARY
CatcalIs, SqueaIing, Frying and Other Noises Can Be Removed if Small Details
 Are Observed

When some radio fans try to oper- ate a loud speaker with their receiv- ing set. the result sounds like ton of coal being dropped down chute into the cellar. This Is varied in many instsSces by n series of noises that in many respects correspond to the nightly concerts of the feline tribe. Both of these conditions are due to perfectly we'll defined causes and can be eliminated, or at least so com pletely modified as to make them eglgible.
 In the first place they are chiefly due to the fact that some fans really believe a tin horn attached to tele- phone receiver makes a loud speaker and that It amplifies sound. This is just the same as pilots of aircraft who imagine they can hold the ma chine up in the air with their hands after the engine has died out. You cannot get loud speaking results with q tin horn alone, any more than you can hold an airplane up In the air with your hands.
 It is quite possible, of course, to utiliss a tin horn attached to a tele- phone receiver for tho purpose of getting loud speaking results. but the volume must be there in the tele- phone receiver before this can be done. The horn merely directs the volumekof sound forward in the same 10 the mouth directs the speech in one direction and enables the sound waves to travel further in one par ticular direction.
 Caused by Too Much Current
 have given this explanation in order to prepare the way and show what is the cause of the frying" and ''cat calls" in the so-called loud speaker" It Is caused by the fact that the operator. In order to get re- suits out of his makeshft apparatus. puts too much current on the vacuus tubes in his sets, and the result is that they get real angry and growl and howl. That Is one of the primary causes as l have gathered from. a great deal of the correspondence re- cetned from radio fans. Another cause is in the design of the appa- ratus itself. and this applies partieu larly to sets that have been assem- bled or constructed by novices them selves.
 When using tho vacuum tube de- tector alone these noises will not be nearly so apparent, particularly If the vacuum tube Is not In a regenera- tive circuit. It Is when we come to the question of amplification that this takes place. 1t must be under stood that with frequency am plification we are increasing the volume of frequencies that corre- spond with sounds audible to the human ear That Is, frequcncies which do not range higher than 5000 vibrations a second.
 Now the transformers that are used between each of the amplifying vacuum tubes are designed especially to Increase or amplify frequency bands that correspond to the rapidity of vibrations which are audible. Therefore. if there is any noise from the detector or from the first am plifying bulb which comes within this range. it will be amplified and reproduced in the telephone re- ceivers.
 In this connection 1t Is imperative that all wires which connect the va rtous pieces of apparatus together should be as short as possible. This is particularly true of the leads to the grinds of the simplifying tubes.
 Connections Must He Tight
 Another very important thing is the connections themselves They must be absolutely tight and should be soldered together wherever possibie. If there is loose connection anywhere
 
 tneA loese wire will vibrate This vi- bration can be caused by any jarrirg, such as street traffic or any one of the hundred and one things about che house. and everytime a loose wire vibrates 1t temporarily disconnects the set and connects 1t up again. in- terrupting the steady function of the circuit and causing noise to be re- produced in the telephone receivers, and since this has passed through the amplifiers 1t will be increased lr volume with every stage of ampli- fication.
 You have undoubtedly heard the phrase tube noises" This can be caused by poor tube or by tube that does not sit tightly In it's socket or makes an imperfect connection on the base of the socket. This should be watched for very carefully In fact, 1t may very often occur that an improvement in the reception can be obtained by switching the ampli- fer tubes around.
 For detector purposes a soft tube is invariably recommended In this case a great deal of attention must be paid to the amount of current in the plate circuit as soft tube is what Is known as a "critical tube" This means that each tube will wary and consequently require a different amount of voltage on the plate cir cult. % that 1t Is very necessary to have . "B' battery for the detector tube that 10 variable and will per init you to take off any amount of voltage. In no case should this vol tage be more than a standard 22a volt.
 Difference Between Tubes
 x as an amplifier. hard tube can be used as a detector with very steady results. The difference between the hard" and the >"soft" tube is the quality of the va Yum inside of tlie glass bulb.
 In order to get vo, Qe sufficiently large enough to ol Sate, an inn provised loud-speaker, Such as t.n horn attached to one end of the tel ophone receivers, it will be better to use 5-watt power tubes as amplifiers instead of the standard amplfying tubes. In this case. as much as l50 volts can be placed on the plate cir cults of the 5-watt tubes. but before using such tubes. 1t Is very necessary to determine whether the, audio- frequency transformer will stand the voltage that will be applied to- them With such tubes, in the majority of cases, 1t will be quite possible to obtain sufficient volume to operate a loudrspeaker such as you describe above.
 Some of the frying noises caused in the loud speaker originated from the "B" batteries. These should be watched very carefully, and if they give any trouble should be replaced Gome of this trouble can be elimi- hated by placing a fixed condenser across the B" battery. Such a con denser can be purchased in a flat. metal container, and its capacity should be either or mfds.
 Another aid. is grounding the posi-