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Show (Edited by G. Douglas Wardrop. Editor of Radio Merchandising.) i Showing Circuit Diagram of the Conventional Three-Coll Honeycomb, but With Slight Modification. By HERMAN A. FISCHER After having constructed, torn npurt anil rebuilt many kinds of receiving sets I deckled that the next one would le a permanent fixture. This, however, was not an easy matter to do, as the market was saturated with a large assortment as-sortment of new circuits and designs. My main desire was to have a set with which I could experiment and change about, but still have an outfit constructed con-structed In a cabinet w hich would present pre-sent a finished appearance. After careful consideration the set which I will describe was decided upon, and after testing I found that It met the rigid requirements in every respect. The circuit is of the conventional three-coil honeycomb, but with slight modification. A list of parts required to complete the outfit Is as follows: One panel. 7 by 24 inches ; 1 cabinet, 7 by 24 by 6 Inches deep ; 1 three-coil honeycomb mounting; 2 .001 mfd. vernier variable condensers, 1 plate variometer, 1 rheostat, rheo-stat, 1 socket (combination preferred), 1 mica grid condenser with G. L. mounting, 1 antl-capaclty switch, 3 4-inch dials, 1 rheostat dial, 14 binding bind-ing posts, 5 lengths buss bar wire, 2 extension handles for H. C. mounting (hard rubber or bakellte). Adaptable to Use of Amateur. This set was designed as a combination combina-tion long and short wave tuner and is adaptable to the use of the amateur, broadcast listener or ex-cominercial operator who enjoys copying a bit of 600-meter traffic or press on longer waves. Care must be taken w hen wiring the anti-capacity switch. Needing only a double-pole, double-throw switch, and as the anti-capacity switch I used was a four-pole double throw. I soldered the two poles together on each side. S-2 in the diagram Is a small single-pole, single-pole, single-throw push-pull dashboard switch or, as in my case, a small push-pull push-pull canopy switch, as used in electric fixtures. This switch opens the plate to the tickler coll for regeneration by the feed-back method on waves above 525 meters (determined by size of variometer) and closes circuit, so that tuned plate regeneration Is used on the lower waves. It will be noted that the plate variometer Is In series with the tickler when S-2 Is open. This will allow the plate to be tuned to a certain cer-tain extent on the upper wave lengths. Size of Honeycomb Coils. The wave lengths which this set will cover depend on the size of the honeycomb colls used. However, the et Is not limited to the use of honey- combs only, which Is the reason for the six binding posts over the honeycomb honey-comb mounting. The leads from the honeycombs, being flexible and having solder lugs as terminals, can be easily disconnected from the posts (connections (connec-tions being made from the outside), and the set is ready for experimental purposes. If the user desires to try a new varlo-coupler varlo-coupler which he has just completed he may do so by connecting the varlo-coupler varlo-coupler primary posts to the primary posts on the set and the varlocoupler secondary posts to the secondary posts on the set. Keeping S-2 closed he will secure regeneration by tuning the plate variometer. His primary and secondary sec-ondary circuits are tuned by means of the primary and secondary condensers In the set. - Suppose he now wishes to experiment experi-ment with the much-abused single circuit. cir-cuit. Removing 1:1s varlocoupler from the circuit, he connects a buss connection connec-tion from primary post No. 1 to secondary sec-ondary post No. 1 and one from primary pri-mary post No. 2 to secondary post No. 2. He then either has the choice of connecting his secondary honeycomb coll In the circuit or use of an external exter-nal coil. Setting the secondary condenser con-denser at zero and tuning with the primary condenser In series, he has his standard single circuit, using either tuned plate regeneration or feed back. Other Combinations. These are only a couple of the combinations. com-binations. Others will suggest themselves. them-selves. I am using an external three-coil three-coil splderweb mounting at present and get fine results. With a combination combina-tion of spiderweb colls I can cover a wave length range of from 17o to 1,000 meters. I expect to be able to get higher wave lengths shortly. With spiderweb coils each of 50 turns as primary and secondary and .OOOo mfd. condensers In the set, ami using the plate variometer as the method of regeneration. I have beard the following stations in the middle of summer: WGY, Schenectady, loud and clear; WDAI', Chicago, fair and clear; WJAX, Cleveland, fair and clear; WBZ. Springfield, fair and clear; WMAF, Dartmouth, fair and clear; besides be-sides all the local stations with the phones lying on the table. On 200 meters I can copy all districts dis-tricts except the . 0 7 in hot weather, and on Otxj meters I hear Canada ami alb itlong the Atlantic coast as far south as NGE, Miami, Fin. This reception re-ception was done on a UV200 tube, with 20V on the plate, and speaks well of the set for Rummer work. New York Sun. |
