| Show vr interference OF RECEIVING SETS each when tuning for distant station acts as a continuous wave transmitter I 1 we have explained that the ous ons fairly toady will whistles st les usually heard beard while walla tuning for or the distant ata eions was due to a combination of the carrier waves of 0 two stations which were very nearly on the same wave length there Is another series of whistles always present which very much resemble the tha whine of 0 a mosquito both in tono tone and amount of annoyance ino yance produced these are arc calls caused A by the receiving sets acts ot of other listen eni em every receiver using a vacuum tube detector with a regenerative circuit Is a potential transmitter jn fact it contains all tho the essentials of Is radiophone transmitter cc in a small scale I 1 the detector etor tube when oscillating produces oscillation exactly similar to the carrier wave ot of the radiophone stations the frequency or wave length of tills this wave ran can be vt varl d by changing than glue tho the tuning ot of the receiving i toner tuner I 1 the usual procedure in tuning for or a distant phone station Is its a follows put nt tho the detector tube la in no an oscilla oscillate tl condition after the tuner tins lias been adjusted near the pont where experience I 1 tins has taught us to look for the broadcasting stations then move tile the dial slowly across tile the approximate point where the stations anre usually heard tile alie carrier waves are located ity by it a whistle which starts at tile tho upper limit of 0 audibility and goes down tile the settle until it becomes ito go low that it Is 13 a 0 longer a note at title point tho the act Is in exact resonance reto anil and it if ill alio e tickler coupling or plate tuning inductance duc tance Is decreased until the detector c tube stops oscillating tile ver very y best adjustment la Is obtained for reception of that particular st atlon I 1 unfortunately while tills this listener Is going coins through this operations operation his receiving set Is acting as afi it a continuous co wave transmitter find and Is producing some inharmonious wall nails in the lit phones iones of ills his neighbors who happen to be already on the wave of the lie same station tnt lon tile the continuous wave wae sent tilt out by the receiver combines with the carrier wave of the station producing tin on audible note it UK tilt operator could tune time his bis met act ns as olm dm ply as was described above there would be very little but fee be usually whistle back bach mid and forth across the wave of the transmitting sintina several times often several listeners who have beten bern getting fit the e concert perfectly will get restless between selections and get their tubes to tc oscillating and whistle up bp and down it few dinies all listeners should tie very careful to keep their detectors in it a non oscillating condit condition lort at as much its as possible to reduce this annoyance of interference between receivers opinions seem to vary considerably in regard to tho the amounts of energy inducted int ini tho the antenna by the lie single circuit or conductively coupled and the three circuit or inductively coupled receiving set let previous to ilia introduction of tho aln 10 lo circuit very tory little trouble hall had been exper experienced lend with beat notes irom from rec elOng stations tills this wa no doubt duo due to tile the fact that receiving sete acta were rather fe few v and for far also up lip until a few years ago aeo thore there was it very ey small email percentage percent aeo of c w telegraph and phone stat tomi so that there was no reason mison why tn en amateur should keep tits his tube tuba in oscilla oscillation tio a condition on the contrary he was ivery to keep it just below the oscillating point that belarr tie ilia most sensitive adjustment for spark signald I 1 with elih the telephone and c w tele dropla transmitting 1 I a tube transmitters crime canio the single circuit tuner with its extreme 0 of adjustment which wits was so BO well cd 0 to the tory slurp sharp tuning of the 0 i iview BOW transmitters and with the advent of these ney new transmitters mine came tire necessity for making tte tile detector I 1 tube oscillate to in order to locate a station stai on the wale ale of a receiving tuner naturally raily then the interference between receiving sets became noticeable at about bou the time that the ging I 1 e sets amato nume rolis and this helped to prejudice tile the minds militia of the radio public against this me of re r belver no weier the t fact that the 1 tingle circuit arrived ill at about the dime time with the interference Inte ference was by no rit tans the only renson reason for bellev believing bellevon tn Z this tuner toner to be the racial main cause or of ithe trouble I 1 for instance in A single circuit or er conduct conductively ivell coupled tuner tile the Is ii in regeneration at all points on the th scale till INS beems to show that there Is more re in this circuit in the in du furtively clively coupled type tym the main point of difference 1 Is the clow cle coupling to tho the antenna beins con du clively coupled the coulling coull ng to ahe the antenna Is 13 at maxi maximum murn at bil times tuli causes tile lie rn ra thallon don resistance to be which pee benn me to be the factor that keeps th take ane arm rem oscillating freely without unusually lose clotte be awen plate and ard circuits aliu we nv are led to bel believe eve that tills on a one ene to lo avold avoid it 1 with ather uw listeners la aso 0 o bv bu if we must have minsio circuit turi tun er era the thing to do to reduce the radiation di tion to a is to reduce the size of the antenna a series condenser and increase liter e nse the number of 0 f turn tu in n the t b e inductance this 1 l will alve g lt ra sharper sharp e r tuning and ance there t her e will will b be much less trouble in getting the tube tub to regenerate in many localities there Is it a great rent deal of interference from spark sta ta bioni especially in the cities on the coast or great lakes where there are commercial om mercial stations to handle the ship raffle I 1 these rhese spark stations do not tune lery cry sharply thai ply and even eien it if the eta tion Is located several miles away it ll if often impossible to tune tua them out with the average tuner when tuning for a faint at station ani using amputation there la is nothing more nono nerve wracking than to have a spark station roar in unexpectedly there Is little that can be done about tills this interference it if the station Is in close a change of wavelength wave coneth would do little good even if this were possible if it Is a commercial station elation it Is doing a much more important work than our broadcasters are and of course cannot be expected to stand by for them |
