e THE T Y P E A W AV E M ET E R is a direct-reading dial covers in a single rotation frequencies from

Transcription

1 DRECT- R ADNG FOR N TH S SSUE VARA A - convenient instrum nt for mesuring high frequencies in the lbort:ory, where quite ULTRA- HGH FREQUENCES e THE T Y P E A W AV E M ET E R is Pge Le 'E VOLTAGE CoRRECTON WTll THE NEW DALS WAVE METER - :frequently ese of opert:ion is found to be more importnt thn high CONVENENT lnduc TA "CE CHART ccurcy The direct-reding dil covers in single rottion frequencies from 55 to 400 megcycles This wide rnge of frequencie, which is covered without S"\ itching or chng ing coi1s, is prticulrly welcome in the high-frequency field where n oscilltor my produce :frequencies quite d i fferent from those for which the circuit ws 758-A Wve- tuned circuit The TYPE meter is instrument vrible designed comprising condenser vrible nd inductnce FGURE The vrible condenser is of the stright - line con entionl frequency type The vri ble inductnce is obt:ined by s li ding silver spring which is tt ch ed to the rotor of the condenser, long silver s tri p connected to the sttor Becuse induc tnce nd cpci tnce ried re simultneously, wider rnge of freq u enc y is covered thn in when single only one Mesuring the frequency of n ullr high-frequency bnd ele ment is mde vrible wwwmericnrdiohistorycom oscilltor with Wvemeter tl1e TYPE 758-A

2 FGURE 2 Direct-reding frequency cle of the TYPE 758- W vemeter Loo ly coupled to the mesuring circuit is n periodic indictor circuit A fl Wight lmp tht will light redily with 2-wu oscillt,or is used s n indictor of resonnce f the oscilltor power i not u:fficient to light the lmp, the wvemeter cn be mde to rect on the oscill1-or nd will chnge plte or grid current of the tube suffi iently to determine re onnce The complete unit i mounted in trnsprent but lmost unbrekble cse so tht the indicting lmp cn be ob er ed from ll direc-i:ions Since the loction of condenser nd coil of the wvemeter cn be een from the outside, effective coupling to n oscilltor i obtined e il y The two bkeli-i:e end pltes of the completed instrument re cut hexgonl y so tht the wvemeter cn be rested in ny one of six different positions -E KARPLUS Rnge: 55 to 400 Mc, direct reding A c c u r c y : 2 0 Reson n c e n d i ct or : lncnde cent l m p Type SPECFCATONS De cription Dimensions: 47;1' x 4Ys x 4% inches, over-ll Net Weight: 1 pound, 10 ounces Code Word Price 758-A W emeter WTrY 2800 FrGURE 3 Two iews of LJ1 TYPE 758-A W emeter with the vrious prt identifi d SLVER-PLATED PLATES HEAVY ROTOR PLUES GENER AL RADO 2

3 3 EXPERMENTER L NE VOLTAGE CORRECTON WTH TH E VARAC e VOL TAGE CORRECTON on under-voltge or over-voltge ines is coilllon use for Vrics Figure 1 () shows the simplest connection for this purpose With this circuit line whose voltge vries by ±13 per cent cn be kept t its men rted vlue The rted currents, only, cn be drwn from the V ric when the line voltge is t its minimum When the line voltge is high so tht the V ric is used s stepdown trnsformer, the flux density is higher thn norml, which resul s in somewht greter heting Figure 1 (b) i llustrtes similr method, differing only in tht line nd output connections re reversed The method hs the dvntge tht the Vric lwys opertes t its rted Hux density n using this method it is dvisble lwys to return the brush to the neutrl position (ie, to position over tp 4) before strting opertions f the brush is set for mximum step up, nd the line voltge hppens to he t its mximum, ex es ive no-lod urrents y be drwn by the Vri nd it my become overheted The rted current of the Vric my he drwn t ny line voltge within the rnge of regultion igure 2 () shows circuit* using V ric bridged cross section of tpped utotrnsformer This circuit is especilly useful with line oltges higher thn the rted voltge of the Vric nd in cses in which it is desirble to u e the full rottion of the V ric for fineness of control Line currents up to the r1:ed current of the Vric my be used Figure 2 (b) i the inverse of Figure 2 () nd hs the sme uses Lod currents up to the rted current of the Vric my he drwn Figure 3 shows circuits which re prticulrly useful where smll line voltge vritions re required nd where the currents to be dr n re greter thn cn be supplied by ny stndrd V ric n igure 3 () Vric cross the *P K MeElroy, "Extending the Field of Appliction of the Vric," Generl Rdio Experimenter, Volume XV, o 5, October, volts , volls LNE OUTPUT FG (l FG 2 () -130 volt& OUTPUT 115volts LNE FG ( b) wwwmericnrdiohistorycom FG2(b)

4 wwwmericnrdiohistorycom GENERAL RADO 4 LNE line delivers controllble voltge to the full winding of n uxiliry utotrnsformer, prt of whose winding is in series with the lod With the V ric brush in the 5 position, 1:he series voltge in1:roduced into 1:he output circuit by the u iliry "trnsformer is zero, nd line nd output: voltges re equl Rottion of the brush increses or reduces the output voltge by n mount depending on the turns rtio of the tr n former nd the po ition of switch S2 FG 3 (l FG3(b) o------' FG3 (c) O\JTPUT 6 T J OUTPUT Assuming tht the line voltge to be compensted is t its m imum, we strt with S2 in position nd the brush t position 1 As the line voltge drops, the output cn be held constnt by rotting the brush to rd po ition 5 This gives continuous control until the line voltge flls to norml output voltge f the line fll switch S1 is clo ed, switch below norml, 2 is thrown to position b nd then switch S1 is opened This ope rtion chnges the uxiliry trnsformer from step-down to step-up trnsformer without opening the output circuit The output cn now be kept t its norml vlue by rotting 1:he V ric brush bck towrd position 5 s 1:he line voltge fll to its minimum Obviously, in the cse of line which is lwys too high or lwys too low, the switches my be omitted nd the full rnge of control oh-tined by single rottion of 1-he V ric brush Output currents up to rted current of the V ric times the turns rtio of the uxiliry trn former cn be controlled Figure 3 (b) gives the sme type of control s the circuit of Figure 3 () The opertion nd uses of this circuit re the sme s for Figure 3 () except tht the use of n inductively coupled trnsformer obvites the nece sity of using shorting switch to keep the output circuit lose d while the reversing switch is being operted Figure 3 (c) gives method by which desired output oltge my be obtined from either higher or lower line without the neces ity of ny witching This me1:hod re quires the u e of center tp on the Vric t Figure 3 (d) shows n obvious extension of Figure 3 (c) which is useful in cses where the line voltge is higher thn the rted voltge of ny stndrd Vric - S BucK GHAM tceoter t[l re provided on 230-volt models LNE FG 3(d)

5 wwwmericnrdiohistorycom NEW DALS e T H E T W 0 - N C H D A L used on everl Generl Rdio instruments hs now been mde vilble for generl sle Two types re listed, one with divisions for 360-degree rottion, nd the other with divisions for 180-degree rottion Both models re drilled for -inch shft A new four-inch dil with divisions for 360-degree rottion is lso vilble in both direct- nd friction-drive models These new dils re mde of nickel silver with photo-etched scles nd TYPE 637 Knobs All dils re insulted from the shft An indictor, s shown, nd drilling templte re supplied with ech clil FGURE 1 View of the T YPE 717-K or 717-L Dil The dil i shown pproximtely % ctul size Type hft Dim Dil Arc Divs Friction et Code Drive Rtio Weight Word Price 4-lnch Dimeter -Type 703 Friction-Drive Dils 703-K ;!iv 360 1: 5 $ L %" 360 1: 5 8 oz DHlP oz DHOP 4-lnch Dimeter-Type 717 Direct-Drive Dils 717-K ;!i" oz DHUG L %" oz DKEG A ;!i " lnch Dimeter -Type 701 Direct-Drive Dils 2 oz DLAP K ;!i" oz DL X 125 FGURE 2 View of TYPE 701-K (left) nd TYPE 701-A (right) Dil The dil re hown pproximtely% ctul size 5 EXPERMEN TER

6 wwwmericnrdiohistorycom GENERAL RADO 6 A CONVENENT NDUCTANCE CHART SNGLE-LAYER SOLENODS FOR H-H-H-+-Hl H-1-+J-F 5 0 OO llhllllllllllllllllb H m+-++t -H-++t +t -H-++H+-H-+-+-t H+H-rH-tffi l-h-+h+ m-t+th-i+ 10 lo ( = ool 0005 ' Ud:::c:::LLJJJJWWWJLJJWWWwJLJLJWwJLUJdJJJWJLWL1JJW:WW1-WLJLUJ

7 wwwmericnrdiohistorycom 7 EXPER MENTER 0 :: () z ::: <{ w z _J :: UJ en z 0:: :::> / - "' _, ro B & S GAUGE Wt RE e 0 N T H E S E T W 0 P A G E S re r nted chrts for dete1 mining the numb r of turn nd the ize of wire to be used in ord r to obtin gi n indu - tnce on given w jncling forn1 n the left-hnd hrt the vrib]e l re n th number of turn, nd il' th rtio of winding Jength to winding dimeter The rtio of inductnce to dimet r of winding ( ) i used prmeter The cur es were compu ted from the expression gi en in Cir ulr 7 4 of the U Bureu of tndrds, *which, using he t rminology of th chrt, my he written, L = n2d2 K l where L is the inductnce in µh K is N gok 's onstnt nd d nd l r in in he * Rdio nstruments nd Mesurem nte," p 252 (1)

8 wwwmericnrdiohistorycom GENERA L RADO 8 turn For given inductnce the nmnber of is then, n = ( ) ( ) (3988) ( ) (2) This form of the expression is prticulrly convenient becu e, in designing coils, the engineer usully strts with l given coil form ( d known ) nd needs The second chrt is plotted from tndrd winding dt publi hed by wire mnufc1:urer s n exmple of the use of th e chrts, consider the problem of de ign ing coil of µh inductnce on winding form two inches in dimet er, wi1h n vilble winding spce of two inch s l Th L e quntity di un 1ty n d d is 50 E n- L tering the chrt t d = 50 nd following given inductnce L ( esily clculted) Since N gok 's constnt depends on l the rtio d' the use of this rtio for the horizontl scle mkes ll the curves prllel, so tht, in plotting them, only one curve need be lculted The other cn be drwn from templte For interpolting between curves, logrithmic scle covering one decde of is shown t the right of the chrt down the curve to the verticl line = 1, we find tht n, s indicted by the lefthnd verticl scle, is 54 turns With winding spce of two in hes, this is equivlent to 27 turn per liner inch, close wound The second chrt shows tht o 18 enmel or singlesilk-, No 20 double-silk-, or singlecotton- or No 22 double-cotton- o ered wire would be used close wound o 25 bre wire, double spced, could l o be used ERRATA T HE FOLLO WNG ERRORS o curred in the rti le entitled sub titution Mesur ment t Rdio Frequen ies," by R F ield, ppering in -the M, 1940, issue of the Experimenter 1 The vlues Le = 0006 µh d Re = 0005 n pply not to the TYPE 722- Preci ion Conden er stted, but to newly designed condenser used in the TYPE 82 1-A Twin-T mpednce M - uring Circuit, whi h wijl be de rib din fort hcoming is ue of the Experimenter 2 n Tble, first column, fourth line, RL should be R GENERAL RADO COMPANY 30 STATE STREET CAMBRDGE A, MASSACHUSETTS BRANCH ENG NEERNG OFFCES 90 WEST STREET, NEW YORK CTY 0 NORTH SEWARD STREET, LOS ANGELES, CAL FORN A