US 2325174 A
Description (OCR text may contain errors)
July 27, 1943. A. H. COOiPER TUNED CIRCUITS FOR WIRELESS RECEIVERS Filed April 21]., .1942
70 AMPuF/m j 2: 721 AMPL mm INVENTOR. Air/we flaw/FY (oo s/ ATTORNEX i Patented July 2 1943 rime. c wwsae .BECEIV 1 .:Arthur JienryrCwpe Buchinghams ra llng E ici8:;Musica i1n mir es.if .L' e eH i ess ilan ias i n 1 -Applicatin:Aprilfil, 1942,'Se1 ial No. 439,350
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core or magnetic material isemployed inside a solenoid. This type of tuning inductance is most convenient for receivers covering only one Wave-' band; the addition of a further band leads either i to unsuitable ratios of inductance to capacitance or else to the need for additional components. in receivers with bandspread tuning in some wavebands, the complications are likely to be serious. 7 I
The object of the present invention is to provide inexpensive waveband spreading tuning means in a circuit employing permeability'tuning and involving he use of a vary few components.
According to the present invention a tuning circuit includes a single permeability tuned inductance which serves as the main tuning adjustment means over frequencies in one tuning range and as a fine tuning adjustment means at frequencies higher than those in said tuning range.
A particular formof tunin circuit according to the invention includes a single permeabilitytuned inductance shunted by a condenser which may be variable, the frequency bandwidth covered by said inductance and condenser being extensible by the addition of an alternative shunt condenser, tuning to higher frequencies being effected by the addition of an inductance in shunt with the first inductance together with a suitable condenser or condensers in shunt, the arrangement being such that the permeability-tuned inductance operates as a fine tuning control at the higher frequencies.
The tuning inductance can take care of the medium Waveband, for example, and can easily be arranged to cover the long waveband by the connection of a suitable fixed condenser in shunt. On the short waves, the tuning inductance can be used to provide fine tuning in the spread bands by connecting suitable values of fixed inductance and capacity in shunt so as to center the tuning range in the frequency ranges required, the ratio of the fixed inductance to the fixed capacity being so chosen that the desired tuning, range is provided by the tuning inductance.
In order that the invention may be more clearly unde rst'ood and readily 1 carried into efle'ctg al- 'ternative circuits embody g 'the invention will 1. wbe described in grea fdetail by accompanying drawing.
'diun1b 'adcastwav inductance required. yrrhe "shu'nt condenser Z'may sa am i-semi 1 1 na zf ar'nple-with'refernbe ftofil igures j neat-re e; 1, the permeabilityto v. i r ,h e,
be fixed or variable. An extension orniawaimband over longer Wavelengths is obtained Without the addition of variable inductance merely by arranging the wave change switch 3 to increase the capacity across the variable inductance I by the substitution of a shunt condenser 4 for the condenser 2. band over shorter wavelengths, again Without the use of additional variable inductances, is obtained by arranging the wave change switch 3 to remove the shunt condensers 2 or i and to connect in their place in parallel withthe variable induct-- ance l appropriate tuning elements such as inductance 5 and condenser E, or inductance! and condenser 8. It will be clear that the provision of pairs of shunt components provide suff cient degrees of freedom to allow both the mid-frequency and the spread of each band to be given a any reasonable values.-
In a receiver with several bands, various components may with economy be shared between ,Wavebands; As an example, Figure 2 shows a method of sharing condensers such as, could be v performed if the values of condenser 2 and condenser 8 in Figure 1 were found to be substantially the same, by splitting up the wave change switch Sinto two ganged sections 3 and 3a, one
selecting condensers and the other inductances. v 1 7 It will be seen in Figure 2 that by providing 'a a lead 9 from the end contact of the switch contact arm 3 to the condenser 2 and by providing two dead contacts for the first two positions of the V switch contact arm 3a, the equivalent arrange ment of Figure l is provided except that in the extreme right hand position of the switch contact arms, the condenser 2 will be connected'across inductance 7, thus eliminating the condenser 8 of Figure 1.
Variation of the position of the adjustable iron core cooperating with the variable inductance I in Figure lior 2will tune the combination of shunt inductance over a range adequate to cover one of the allocated broadcast bands, although the tuning is not linear.
The invention will be found to be of particular application to the design of low priced radio re-' Further, an extension of the wavetuned inductance, a condenser and a circuit com-' prising inductance and shunt capacity, and means for selectively shunting the condenser or the latter circuit across the permeability-tuned l inductance, the arrangement beingsuchthat with,
the condenser shunting the permeability-tuned inductance the latter serves as the main tuning p means in one of the wave bands, and with the circuit of the inductance wand shunt capacity shunting the permeability-tuned inductance, the
latter serves as the fine tuning means in another,
higher frequency band.
2, A tunable circuit comprising a. single per meability-tuned inductance and a shunt condenser of such values 'to tune the circuit over 7 one, wave band, said inductance serving as the tuning means in said band, a circuit corni prisinga fixedinductance and a shunt capacity, =tunedito the mid-frequency of a band of higher frequencies than the first band, and means for substituting thelatter circuit for the first mentioned shunt condenser across the permeability- I tuned inductance, the latter now serving as the fine tuning means in the band ofhigher frequencies..
3. In a receiver; at least" one tunable circuit? ceiver through a band of medium or broadcast 5 frequencies, and means for'replacing the shunt.
condenser with, a shunt circuit comprising an in ductance and a shunt capacity which are tuned. to the mid-frequency of a higher frequency band,. the permeability-tuned inductance effecting band.
10 spread tuningin said higher frequency band.
bility-tuned inductance, a, plurality of condensers: and a plurality of fixed tuned. circuits, means for selectively connecting one of the condensers or 5 one oi the fixed tuned circuits in shunt across the permeability-tuned inductance, the values of said elements being such the receiver will be tuned to different frequency bands depending upon the position of the selective means, the permeabilitytuned inductance serving as the main tuning means when one of the condensers is shunted thereacross, andsaid inductance serving a the fine tuning means for efiectin-g band spread tuning when one of the fixed tuned circuits is shunted g5 thereacross. I v
5. The invention as defined in claim 4 Where in at least one of the condensers serves also as an element of the fixed tuned circuit.
30 V ARTHUR HENRY COOPER.
' 4'. In'amulti-band receiver, a single permea--