A New Wave Trap

Radio Record, Volume III, Issue 4, 9 August 1929, Page 30

A New Wave Trap

Advantages Claimed A DEVICE akin to a wave-trap, which is said to be very effective for cutting out unwanted stations, was described recently in the "Manchester Guardian." It incorporates a plug-in or solenoid coil of 35 to 60 turns, tuned by a’ .0005mfd. variable condenser in parallel. One end of the coil is connected to the earth terminal. of the set and the aerial is attached direct to the other. Another lead is taken from the aerial end of the coil to the aerial terminal of the set, and in this lead is inserted a seven-plate neutralising condenser or a compression type variableee rrr rrTTrririciriiirit) ~

PRESRERCRRSSCCRRSERR SRR RCERRSES SSPE ROC ERS ASSL CEES EAE fixed condenser with a maximum. ca~ pacity not exceeding .0001mfd. The best size of coil can be found 4 experiment, but’ 50 turns is a fair erage for the broadcast band. he small condenser is generally set -with its vanes all in, but may be adjusted as required. .Some constructors may regard the inclusion of another tuning control in the set-the unit must be tuned every time the tuning of the set is alteredas a drawhack, But this is not so difficult ag may at first appear. The tuning condenser of the unit moves in unison with the other tuning condenserthat is to say, if the tuning condenser .of the set is moved up a few degrees the tuning condenser on the unit is also, moved up similarly. After a littles practice this additional operation oecupies only a fraction of a second. Furthermore, this disadvantage may be overcome bythe use of a changover switch for the aerial, which will

New Wave Trap

(Continued from page 30.) allow the unit to be reserved for cases where greater selectivity is desired. — The device is claimed to be moré adaptable than the ordinary wave-trap and to have little effect on the strength of signals received. ~