PROGRAM LADDER
	INTEGER CHAR
	DIMENSION R(100)
	PI=3.14159
	WRITE (3,1)
1	FORMAT (' LADDER NETWORK ANALYSIS PROGRAM')
	WRITE (3,222)
222	FORMAT (
     &' This program analyses a full ladder network for gain and phase'
     &/'  starting at the load and working towards the voltage source.'
     &/' Any null or infinite branches must be declared as such.'
     &/' ...report problems to Trevor Marshall,'
     &/'               SYSOP, Thousand Oaks Tech RBBS (805) 492 3693'/)
	WRITE (3,16)
16	FORMAT (' NUMBER OF BRANCHES (including the load) ? ')
	READ (3,2) A
2	FORMAT (F2.0)
	N=2*A+9
	DO 100 I=0,N
	R(I)=0.
100	CONTINUE
	NN=1
150	FLAG3=0
	WRITE (3,17)
17	FORMAT (' R, L or C ? ')
	READ (3,3) CHAR
3	FORMAT (A1)
	IF (CHAR.EQ.'R ' .OR. CHAR.EQ.'r ') R(3)=1.
	IF (CHAR.EQ.'L ' .OR. CHAR.EQ.'l ') R(3)=2.
	IF (CHAR.EQ.'C ' .OR. CHAR.EQ.'c ') R(3)=3.
	IF (R(3).EQ.3) FLAG3=1
	WRITE (3,18)
18	FORMAT (' VALUE ? ')
	READ (3,4) R(4)
4	FORMAT (E12.5)
	IF (R(3).NE.1) GO TO 200
C	IF (.NOT. CHAR.EQ.'R ' .OR. CHAR.EQ.'r ') GOTO 200
	R(NN+10)=R(4)
	GO TO 300
200	R(NN+11)=PWR1(FLAG3)*R(4)
300	NN=NN+2
	IF (NN.LE.(2.*A-1.)) GO TO 150
	WRITE (3,5)
5	FORMAT ('0      OUTPUT')
	IF (R(11).GT.1E-30) WRITE (3,6)
6	FORMAT ('0OHMS 0----R----O'/'      !         !')
	IF (R(11).GT.1E-30)GO TO 400
	IF (R(12).GT.1E-30) WRITE (3,7)
7	FORMAT (' HY   O----L----O'/'      !         !')
	IF (R(12).GT.1E-30) GO TO 400
	WRITE (3,8)
8	FORMAT (' FD   O----C----O'/'      !         !')
400	NN=3
450	R(0)=((NN-1.0)/4.0-INT((NN-1.0)/4.0))
	IF (R(0).GT.1E-30) GO TO 500
	IF (R(NN+10).GT.1E-30) WRITE (3,9)
9	FORMAT (' OHMS !----R----!'/'      !         !')
	IF (R(NN+10).GT.1E-30) GO TO 600
	IF (R(NN+11).GT.1E-30) WRITE (3,10)
10	FORMAT (' HY   !----L----!'/'      !         !')
	IF (R(NN+11).GT.1E-30) GO TO 600
	WRITE (3,11)
11	FORMAT (' FD   !----C----!'/'      !         !')
	GO TO 600
500	IF (R(NN+10).GT.1E-30) WRITE (3,12)
12	FORMAT (' OHMS R         !'/'      !         !')
	IF (R(NN+10).GT.1E-30) GO TO 600
	IF (R(NN+11).GT.1E-30) WRITE (3,13)
13	FORMAT (' HY   L         !'/'      !         !')
	IF (R(NN+11).GT.1E-30) GO TO 600
	WRITE (3,14)
14	FORMAT (' FD   C         !'/'      !         !')
600	NN=NN+2
	IF (NN.LE.(2*A-1)) GO TO 450
700	WRITE (3,15)
15	FORMAT ('      O  INPUT  O')
C
750	WRITE(3,28)
28	FORMAT('0FREQUENCY SWEEP STARTS AT ? ')
	READ (3,19) R(0)
19	FORMAT(E12.5)
C	R(0)=R(0)/(2*PI)						  omega
	WRITE(3,20)
20	FORMAT('+              AND ENDS AT ? ')
	READ (3,21)R(1)
21	FORMAT(F5.0)
C	R(1)=R(1)/(2*PI)						  omega
	WRITE(3,22)
22	FORMAT(' NUMBER OF INTERVALS ')
	READ(3,23)R(2)
23	FORMAT(F3.0)
	WRITE(3,24)
24	FORMAT('0FREQ.(HZ),MAGNITUDE (DB),PHASE (DEGREES)'/' ')
	C=R(0)
	R(4)=(R(1)/R(0))**(1./R(2))
C	CALL PLOT S/R 'P'
900	R(7)=1.
	X=1
	Y=0
	R(5)=0
	R(6)=0
	R(8)=0
	NN=1
1300	FLAG1=0
	FLAG2=0
	FLAG3=0
	FLAG4=0
	IF(R(NN+10).GT.1E-30)FLAG1=1
	IF(R(NN+10).GT.1E-30)GO TO 1000
	R(10)=R(NN+11)*2.*PI*C
	IF(R(10).GT.1E-30)Z=FLAG2
	IF(R(10).GT.1E-30)GO TO 1100
	FLAG3=1
	R(10)=-1./(R(NN+11)*2.*PI*C)
1000	R(3)=R(NN+10)
1100	ZZ=((NN+1.0)/4.0-INT((NN+1.0)/4.0))
	IF(ZZ)1115,1115,1120
1120	IF(FLAG1.EQ.1)R(3)=1./R(3)
	FLAG4=1.
	IF(FLAG1.EQ.1)GO TO 1115
	R(10)=1./R(10)
1115	IF(FLAG1.EQ.1)X=R(3)*X
	IF(FLAG1.EQ.0)X=R(10)*X
	IF(FLAG1.EQ.0)ZZ=FLAG4*FLAG2+(1-FLAG4)*FLAG3
	IF(FLAG1.EQ.0)Y=Y+PWR1(ZZ)*PI/2.0
	Z=X*COS(Y)
	Y=X*SIN(Y)
	X=Z
	IF(FLAG4.EQ.0)X=R(7)+X
	IF(FLAG4.EQ.0)Y=R(8)+Y
	IF(FLAG4.EQ.1)X=R(5)+X
	IF(FLAG4.EQ.1)Y=R(6)+Y
	IF(FLAG4.EQ.1)R(5)=X
	IF(FLAG4.EQ.1)R(6)=Y
	IF(FLAG4.EQ.1)GO TO 1200
	R(7)=X
	R(8)=Y
1200	Z=SQRT(X*X+Y*Y)
	IF(Y.GT.0)R(2)=PI/2.0
	IF(Y.LE.0)R(2)=-PI/2.0
	IF(X)2220,2250,2220
2220	R(2)=ATAN(Y/X)
	IF(X.LT.0)R(2)=R(2)+PI
	IF(Y.LT.0)R(2)=R(2)-2*PI
2250	Y=R(2)
	X=Z
	NN=NN+2
	IF(NN.LE.IFIX(2.0*A))GO TO 1300
	X=1.0/X
	ZZ=20*ALOG10(X)
	ZZZ=-Y*180./PI
C	CC=C*2.0*PI							  omega
	CC=C
	WRITE(3,25)CC,ZZ,ZZZ
25	FORMAT(F8.2,2(' ',F12.2))
	IF (R(0).EQ.R(1))GO TO 1550
	C=C*R(4)
	IF(C.LE.R(1))GO TO 900
1550	WRITE (3,26)
26	FORMAT('0NEW SWEEP (Y/N) ? ')
	READ(3,27)ISTRG
27	FORMAT(A1)
	IF(ISTRG.EQ.'Y ')GO TO 750
	END
	FUNCTION PWR1(Z)
	IF(Z.EQ.0)PWR1=1
	IF(Z.EQ.1)PWR1=-1
	IF(Z.EQ.2)PWR1=1
	RETURN
	END

.