An Ejector for Any Receiving Circuit

Radio Record, Volume IV, Issue 26, 9 January 1931, Page 17

An Ejector for Any Receiving Circuit

A’ Wavetrap of Unusual Qualities

By

A.A.

H.

I HAVE studied and experimented on yarious ejecting circuits and eventually devised one that was satisfactory .in many ways and working efficiently. It will completely dissolve broadeasting signals at a surprisingly short distance from their transmitter, smooth out rough signals, reduce static considerably, tighten up tuning. to almost a point, and also form an adjunct to a highly efficient crystal receiving set. ° It is best to ‘be constructed as a wave-trap, alone and hooked’ up permanently to the receiver, for it does not, diminish the volume and_ often improves it. -Station 1YA ‘faded out" within a quarter of a mile away and when " signals were strongest, and Australian stations brought in. ~ On a good cardboard former,’ which may be from 24 to 2% inches in diameter, and about 8 inches long, . fix with glue match sticks minus their heads from # to 7-8 inches apart and wind on closely and tightly about 40 feet of No. 22 D.C.C. copper wire, leaying some six inches slack at each end, after anchoring, for connections to aerial and receiver respectively (see Figure 2). This is the primary (P) coil, Over the centre ofe this coil fix a band of tissue paper, one layer, about an inch broad, and over this, wind on ten turns of No. 18 D.C.C. copper wire as before, and same direction, ‘anchoring each end, leaving about 6 inches of slack. These turns can be

kept in place by threading: over and above at"two or three. places. This. is the secondary (8S) coil, each end being connected to the terminals of the condenser, which should be fastened on to the formico panelling, the coils being’ placed in.an' oblique. position to it when connected.’ Efficient soldering must .be . adopted wherever possible, even to the set terminal A, if the Sector has to be per= manent. ‘In tuning, use "both dials until signals are at the loudest. . The interfering signal ean be -then trapped out; or again, trap out the interfering sig-; nals and tune in those desired with the dial on the set.. ‘A little practice. may. be necessary as this apparatus, if, well made, is somewhat critical in using. By running’ X through .a crystal detector, thence through phones and. on, to connection Y, or, better still, connecting X' and Y to a double * point switch and wiring them as just said, reception can be. had by either valve or crystal receiver at will. In this case the arrow point goes to earth.’ The trap will also smooth out rough signals, reduce static, and it also has improved both tonal and tuning qualities often enough. It does not diminish volume and the writer. knows quite well it will solve many of the complaints from listeners that appear from: time to time. ‘This circuit does not assist short-wave reception. : For crystal work. connect arrow: point to earth.