7412533623

Tube-Transistor “Carrier Switch”

By DAVE STONE

/Use power linę for remołe conłrol wiłh łhis easy-ło-build and easy-ło-align carrier-current łransmiłłer and receiver.

CARRIKR reccivcr and transmittcr systcms are “old hat" in the field of elect ronić remote-control de-vices. They are a time-tested means of using the power lines to carry a trans-mitted low-power. low-frequency radio signal to operate a remotely located re-ceiver relay unit. The receiver relay set can operate other electronic equip-ment, turn on motors, lights. open garage doors and. in generał, conłrol many other types of appliances which need to be turned on or ofT.

Today’s miniaturę components lend themsehes readily to the construction of compact transmitters and sensitive receivers for carrier-control work. This transmitter-receiver combination is un-complicated, easy to construct and align. and is very reliable for operation over moderate distances. It uses standard components and best of all. it calls for easily obtained TV replacement width coils for the tuned circuits so coil winding is unnecessary. The fre-quency can be varied from approxi-mately 60 to 80 kc. and the Iow power output of the transmitter precludes in-terfering radiation from the power linę.

Circuit

The transmitter uses a 6AQ5 in an electron-coupled oscillator Circuit, as shown in Fig. 2. This Circuit arrange-ment is very stable and tends to keep power-line yariations from loading and affecting the oscillator freąucncy. L_x with C, forms the tuned tank Circuit for the oscillator section. with feed-back obtained from the cathode winding into the grid Circuit. The piąte tank Circuit. La-Ca, tunes to the same frequency established by the grid tank and couples the signal out to the power linę via L»'s secondary. Cs blocks the a.c. linę from being short-circuited through the secondary winding and RFC i keeps the r.f. output from being shunted by the power transformers primary winding. This insures that all the output is sent into the linę.

The transmitter power supply is compact, consisting of a smali power transformer, selenium rectifier, and miniaturę elect rolytics. The trans-mitted signal is simply turned on and off with the “Carrier On-OfT” switch S, which applies “B + ” to the 6AQ5*s screen grid and piąte. R, is the filter resistance and R- provides bleeder ac-tion by serving as a constant load to the power supply when the “B-f” is disconnected in the "Carrier Off" po-sition.

The transmitted signal enters the receiser (Fig. 1) through the tuned Circuit La-Ci- and is detected by the 1N34A germanium diodę. The amount of rectified signal applied to the base of the 2N35 n-p-w transistor is con-trolled by the “Sensitivity" potenti-ometer. The two transistors are con-nected as a d.c. amplifier Circuit and the resulting amplified current in the collector of the 2N43 p-n-p transistor operates the 8000-ohm sensitive relay. The 1N69 germanium diodę in the emitter of the second transistor pro-

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Ri—1000 ohm. V₂ »*•

Rj—10*000 ohm linttr laper carbon poi R*—4700 ohm, ^l/₂ w. rei.

Ci—.01 m/-. 600 V. dii€ capecUor Ci*—}00    600 y. diic Cćpacitor

Cir-~f ^ minisiure eltc. capaeitor CRr—lN)4A ltrmenium diodę CRr—lN69 germanium diodę

Alt/—S.p.d.l. 8000-ohm temiliye relay (Sigma 8000 CDS or equi*aleni) ii. Jr—Pin ieck Br—9-12 v. baitery Sr—D.p.d.l. loggie swileh

Vi-fn.p.n" iramiitor (2Nif)

Vs—“p~n.p" iramiitor (2N4i)

Fig. 1. Circuit oi the transistorized carrier-current receieer. ►

Front views oi the complete carrier-current unit with the transmitter at left and the receirer at the right in this photograph.

ELECTRONICS WORLD

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