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going into mu ch detail about here are those which employ vacuum tube s or transistor s as their «active devices " or amp lifying elements, although other kinds ate possible. Some of these other kinds include magnetic amplifiers, which change the cou pling in special kinds of tra nsformers, and diode amplifi ers, which mak e use of special properties of certain special kinds of diodes. The commo n types, though , use tubes or transistors, and since thos e are tJ:e ones covered on the FCC exams, they're the on es we' ll concentrat e upo n in this course. In these amplifiers, the " power" characteristic of a signal which we men tioned a few Jines back is of critical importance, since almost all co mmon am plifier circuits make use of th eir active devices as variable resistances whi ch "valve" steady new power fro m a power supply int o the output circuit, under con trol of the input signal. We've already examined this action in vacuum tub es and in transi stors. The only new poin t we're maki ng now is that th is variable-resistance property of the devi ce is the normal situation in most practi cal amplifier circuits you're likely to run across. As we saw mu ch earlier, the relationship bet ween volt age and current at any one poin t in a circuit may be described in terms of resista nce or , mo re generally, impedan ce. Since most practi cal amplifiers operate with ac signals, "impedan ce" is the way it's specified. Th e characteristics of an amp lifier's ports are usually described in terms of their impedan ce level, an d eith er the voltage, current, or pow er to be applied there. With impedance specified , voltage, curre nt, and power are virt ually int ercha ngeabl e unit s, since the current or th e power may be calculated if voltage and impedance are known, and similarly voltage may be calcu lated if cur re nt or powe r and impedance are known. This spe cificatio n is usually given in term s of th e ma ximum signal level, and it's not at all uncom mon to find an amplifier's inpu t rated in volt age/impeda nce while the output is rated in watts. Many hi-fi rigs, for instan ce, are rat ed for a maximum SOW out at l 6n , and maximum 0.5 V in at sao kn. These port ratings are important, but they do not normally tell us muc h about the amplifier's performan ce. Perform an ce of an amp lifier is usually described in terms of gain and distortion, but this may vary depend ing upon t he use to which th e amplifier is to be put. The gain may be given eit he r in decibels, or as a ratio , so that it bec om es difficult to compare amplifi er ratings. A ty pical rf linear amplifier might be rated for 10 dB gain , in put and out put impedan ces of 52n, and requi re I DOW input for maximum out pu t. Such an amplifier wou ld produce I kW ou tp ut (IO dB gain wit h inp ut of lOOW). A hi-efi rig, on the other hand, might co mpletely neglect to mention gain and merely give out put and input levels together with distortion percentages. Regardl ess of ratings, any no rmal amplifier op erates by regulating the flow of current in its out pu t circuit. If the amplifier is inte nded for use as a voltage amp lifier (o ne in which the power gain is used to step up the signal voltage rather than signal 6-rt-- ·r T OUT •• Fig. 2. Most common amplifier o utput cou pling circuit at audio frequencies is resistance-coupled version sho wn here. Lower capacitor is not obvious on most schematics since it is called a bypass capacit or, but it serves the purpose of taking o utput as voltage drop across load resis tor. current), the resulting variation s in output current flow are converted back into voltage variations by means of a coupling device which may be a transfor mer , a resistance, or an impedance . Most of today's amplifiers use resistance coup ling (Fig. 2) ; as the current through a resistor in series with the active device varies, so does the voltage drop across that resis torv This 64 73 MA GA Z IN E
When it comes to grea t used mo bile communications equipment, we wro te " the book" . . . Send to r a tree copy at " the book" (our new ca talog). Here are onty a tew at our LOW PRICES : 2 METERS GEN ERAL ELECTRIC MAlE33 6 or 12 volts, 30 watts Vibrator Power Supply with ac cessori es $140.00 MOTOROLA X43GGV, New Low Pri ce, Special Mode l in 10" case, 30 watt, transmitt er narr ow band, recei ver wide band, vibrator powered, 2 Ir eq. transmitte r, and tran sistor powered 2 Ireq. " Private Line" receiver (single squel ch), less reeds , complete accessories ..... $100. In quantities at ten ....$00. 6 METERS MOTOROLA FMTR140D,6 or 12 volts, 60 w att , w ide band . Dynamotor Power Supply $40. Transm it ter Narro w Band $50. Fully Narrow Band $60. comp lete with accessories (less accessories deduct $15) GEN ERAL ELECTRIC PRE-PROGRESS 4ER6 RECEIVER, ET5 OR ET6 TRANSM ITTER 30 or 60 watts (as avail able), 6 o r 12 volts, inc luding all accessories $20. UHF MOTOROLA ..• T44A6A with accessories $30. T44AAV with accesso ries $48. RCA CMU15A. ,. 15 watts/minus ac cesso ries $10. For Your Convenience SCHEMATtC DIGESTS. (Po" P,id) G.E. SCHEMATIC OUTLI NE AND INTERCONN ECTION DIAGRAMS FOR GE 2·WAY FM RADIOS. Vol . 1 Pre-Pro gr ess Line ('49 - '55) 25-50 MHz 72-76 MHz Vol. 2 Pre-Progr ess Line ('49 - '55) 150-170.405-425 MHz, 450-570 MHz each vol ume $4.50 MOTORO LA FM SCHEMATIC DIGEST revised edition to 1960 $6.50
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CONTENTS where. Then carne the day
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for ~ bo ut 10 years, has know n Ro
Page 8 and 9:
:l Caveat Bmptor?r ~~~~~.~ ~.~~ *r.
Page 10 and 11:
BOOKS I ADVAN CED CLASS STUDY G U I
Page 12 and 13:
Irving M. Gottlieb W6HDM M~W 931 Ol
Page 14 and 15:
situ ated on a PC board (Fig. 4) di
Page 16 and 17: See your DEALER for DRAKE products
Page 18 and 19: Practical circuit applications usin
Page 20 and 21: INPUT )1 c I SO MHz 1N4381 IOO~ 450
Page 22 and 23: The Mos t Powerful Signals Under th
Page 24 and 25: CA 3028 J.lL 923 '" 4.7 K ., 680 4
Page 26 and 27: K
Page 28 and 29: Theodore Cohen W4UMF 8603 Conover P
Page 30 and 31: ~ ~ Installation of the switch and
Page 32 and 33: A ~Sy CQ, CQ, CQ, t his is K3FEN, R
Page 34 and 35: Messy and m ickey mouse, bu t wh en
Page 36 and 37: The tuning indicat or shown in Fig.
Page 38 and 39: Being qui te activ e on two me ter
Page 40 and 41: "'12V "' 12-24V .60 10K lOOK .I IN3
Page 42 and 43: ON.. EFFICIENCY ORGANIZATION and MA
Page 44 and 45: Bill Hoisin gton K 1eLL Far Over F
Page 46: installation of on e or more low-no
Page 49 and 50: STEP UP TOTELREX Professionally Eng
Page 51 and 52: " 4 ~ O Y " 4 ~ OY ( I U 6 2 11 0'
Page 53 and 54: etter than the "Hot-Water 100 " ...
Page 55 and 56: y Ken W. Ses$ion~ K6MVB DU LD A 8 .
Page 57 and 58: Motorola HEP Semiconductor Devices
Page 59 and 60: see the A1ann for the best in USED
Page 61: esults. The transmitter adj ustme n
Page 65: What Is An Amplifier? Several acres
Page 69 and 70: of am plifier o pera ting con ditio
Page 71 and 72: New advanced 4-band, Communication
Page 73 and 74: LI NEAR NON-LINEAR Radio Amateurs R
Page 75 and 76: 1. T he amp lifier is adjusted to o
Page 77 and 78: many do not) you can either speak a
Page 79 and 80: SOLID STATE ENCODERS for quick and
Page 81 and 82: WHEN IT COMESTO ANTENNA SYSTEMS...I
Page 83 and 84: Richard Tashner WB2TCC 163-34 2 1 R
Page 85 and 86: A. E. McGee, Jr. K5LLI 281 5 Materh
Page 87 and 88: John G. Harder W5QKO/AI4QKO 6200 A
Page 89 and 90: The LOUJ-OhTn JJleter ALL RESISTORS
Page 91 and 92: Photos I and 2 show the meter built
Page 93 and 94: powers of ove r 100W across the ban
Page 95 and 96: ,r-"--'.N=;;EED AN ] CRYSTALS? PHON
Page 97 and 98: 4.000 BIT MEMORY D $8.50 from IBM C
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