Show diagram showing tandem tuning scheme by BOUCK in the new york it Is the purpose of this article to consider the new ideas involved in tuning several radio frequency circuits simultaneously by means of two or more condensers mounted on a single shaft the problems of tandem tuning are really nothing more than the problems of scientific set design slightly emphasized in some respects they are mechanical rather than and in all cases are modified with other problems in individual receiver design there are however some general points which should receive primary consideration before the specific niceties are tackled there Is really only one fundamental secret to successful tandem tuning this Is the matching of indue alv e and values in the in tuning circuits which con aldera the inductance and capacity introduced by leids and wiring it Is the problem of the designer so to arrange his parts and their In that the parasitic capacities and inductances are either negligible or arc the same in each stage of radio frequency amplification this accomplished there remain only the matching of the deliberate inductances the tuning colls and the capacities of the tuning condensers the latter Is taken care of in the case of any reliable condenser such as the amaco amsco siamese which the writer used in his experiments it Is the designers job to match the inductors vernier capacitances and inductors of any tape whatever can be used to balance stray capacities and inductive values as well as poorly matched inductors however no ver aler can efficiently compensate the discrepancies in some tapes of condensers compensation on one wave length Is immediately upset upon tuning to another frequency coils recommended colls characterized by a relatively tow L to C ratio are recommended for use in tandem circuits contrary to general practice in other words space wound colls and similar tricks designed to reduce the capacity of the windings are not recommended n tandem tuning circuits the use of higher capacity colls lowers the proportion of tube and stray capacity to total circuit minimum capacity thus reducing whatever effect tube changing may have upon tuning tandem tuning needless to say can be adapted to practically any tuning messages may travel over separate paths radio messages frequently travel from a broadcasting station to a receiving set over two entirely separate paths piths scientists of the general electric company according to dr B D frees press bulletin the weeks science new york report the dla co ery of further facts confirming this idea oae path Is along the surface of the ground the other pith Is through the high levels of the air fifty or a hundred miles above the earth when both these waves arrive at the same set they sometimes interfere this may cause what radio fans call fading or some other disturbances of reception much progress ani been made recently in understanding just how radio waves move through the ether from place to place As these facts become better known and are applied we may expect further improvement in the quality of the radio gaea sent out part played by tubes on your crystal set crystal sets without tubes are for local stations one tube sets will reach out almost as well as pets if a good aerial Is installed tubes added after the detector add tittle if any to the distance received but do add greatly to the volume tubes before the detector mean sensitiveness ti veness and permit only a small aerial to get the same distance A loop Is not used without radio frequency amplification simplify mg radio fifty feet of wire of little more than pencil thickness hung vertically from the cross arm of a wooden pole 70 feet high has been dishing radio pro to grams from schenectady N Y practically overy corner of the abl taUe aloba system A fundamental panics these notes attention la cu the input or antenna cult the proximity circuit in almost every throw the tuning of th denser out of alignment condition Is especially cot properly compensated r immediately possible ws this the first is to knipf primary with coupling or variable coup ia ly compensated by the 1 e marlc system the present preferable arra B the use of the antenna j denser 0 A certain opi d across primary capacity decided upon by the besl ad or thirty y antenna v lo 10 where between this value pa to r 1 the desired across coll c ev berles condenser of about as introduced as sug gestel 1 denser is varied for in to tennas and left set bhea value Is discovered it M I 1 mended that this con lenss wal ed within th cabinet to P the itching of 0 o anteen campens Com pens alel if two stages of tw oe v quency amplification tn previous to the detector tr one single and one tande a it la advisable to th ked denser across the ferit j this will eliminate the i pens atlon problem at ro pens atlon however la r if only to maintain dial i e almost any efficient sr f the r f stages li t ed for use with tandem r cults the addition of tt s D arann ment presents B 0 B th all grid returns in tl to t common grounded rotor 1 orl down to ohp negative st battery this fact the detector circuit e clency postulates tt to secure nsf shunting the grid ia leak as Is usually doni y grid return Is brocht i esse plus filament tl cw connected between the r I 1 po ment plus of course alk S tandem tuning presents and demands onh te gent application that amsi taa design and building of t e satisfactory to the disca 1 u ale thus last lofb wave length ran how to keep two simple principles of average receiving set all anwa operator to keep in tf i quo waves from to c ay ol 01 coll of wire lg placed in T the antenna it has aims a effect as increasing thet e i antenna thereby matani e to pick up higher ware lc na larger the coll the greater as increase in wave length I 1 it condenser Is placed ins ot antenna or ground vart t length range of the set b the smaller the capacity s i denser the greater will wave length to place an with the antenna connitt il wire to one end of the col wire from the other tera coll to the antenna the set A series cosse i necked the same way length of aerial to get Desire 1 ai use a short aerial and a long outdoor vf ume and distance A be an as easily the two can stalling a pole A switch run a a rooi 11 through one or two the molding in one ha door aerial the end tte u other post Is attached r aerial coining in from center contact goes t w on the set loop aena from the ex perlen arega boers throughout rt been found that f aerial Is abbot 5 P dij outa aa the average w w P aerials are from t |