Pi-L Network Calculator
This is a somewhat different version of a Pi-L calculation program
which computes "real" rather than theoretical values.
The program uses a two pass methodology in which the coils
are first calculated for the tops of the wider band(s)
then the capacitors are calculated at the band edges
and finally the true Q of the resulting combinations are derived.
The initial Q's may be set individually per band which allows for
tweaking the values to accomodate one's real world components or
a constant Q may be set which will override the table entries.
This program is written in the "dead" language of Quick Basic
running under the defunct DOS operating system.
Perhaps, a young computer genius may import the formulae
into a spreadsheet format, the current default vogue.
No error checking is provided against entering silly values but,
the program will crash without harm should a divide by zero
or similar anomaly be encountered.
The output values are written into a text file named "pilX.txt"
where "X" is the selected plate impedance.
*** The Program Listing ***
Note the underscores which denote continued lines for this web posting.
The Quick Basic editor will remove these and restore the program's original format.
REM -- Pi-L Network Calculator by WC6W, Copyright 2005
3 DIM FQ(20), QQ(20), FL(20), L1(20), L2(20): N = 15: CLS
5 PI = 3.14159
10 QZ = 14: REM Use fixed Q if not 0
REM -- Frequencies in MHz
20 DATA 1.8, 2.0, 3.5, 4, 5.4, 7.15, 10, 14.15, 18.15,21.2, 24.85, 28, 29.7,50,54
REM -- Pi-Section Q's
30 DATA 7, 7, 7, 7 , 8, 8, 8, 8, 8, 8, 8, 8, 8, 10, 10
REM -- Coil Frequencies in MHz
40 DATA 2, 2, 4, 4, 5.4, 7.15, 10, 14.15, 21.2, 21.2, 29.7, 29.7, 29.7,54,54
50 FOR X = 1 TO N: READ FQ(X): NEXT X
55 FOR X = 1 TO N: READ QQ(X): NEXT X
60 FOR X = 1 TO N: READ FL(X): NEXT X
REM -- Network Impedances
70 R1 = 4500: REM Plate Impedance
80 R2 = 250: REM Mid Point Impedance
90 R3(1) = 52: R3(2) = 25: R3(3) = 100: REM Output Impedances
REM -- First Pass: Calculate L's at band tops
100 FOR X = 1 TO N
110 F = FL(X) * 1000000
120 Q0 = QQ(X)
130 IF QZ <> 0 THEN Q0 = QZ: REM Force Fixed Q
REM -- Figure Q's
210 Q1 = (R1 * Q0 - SQR(R1 * R2 * Q0 * Q0 - (R1 - R2) ^ 2)) / (R1 - R2)
220 Q2 = Q0 - Q1
230 QL = SQR(R2 / R3(1) - 1)
REM -- Calculate Pi Coils
330 XL = (R1 * Q0) / (Q1 ^ 2 + 1)
340 L1(X) = XL * 1000000 / (2 * PI * F)
REM -- Calculate L Coils
350 XL2 = QL * R3(1)
360 L2(X) = XL2 * 1000000 / (2 * PI * F)
399 NEXT X
666 OPEN "PIL" + RIGHT$(STR$(R1), LEN(STR$(R1)) - 1) + ".TXT" FOR OUTPUT AS #1
REM -- Second Pass: Calculate Network for 3 output impedances
700 FOR Z = 1 TO 3
710 R3 = R3(Z)
720 PRINT #1,
730 PRINT #1, TAB(15); R1; "ohm to"; R3; "ohm PI-L Network"
740 PRINT #1,
750 PRINT #1, "FREQ"; TAB(10); "Pi-Q"; TAB(20); "C1 pF"; TAB(30); "L1 uH";_
TAB(40); "C2 pF"; TAB(50); "L2 uH"; TAB(60); "Mid Z"
760 PRINT #1,
REM -- Calculate at all Frequencies
800 FOR X = 1 TO 13
810 F = FQ(X) * 1000000
REM -- Calculate XL's
820 XL = L1(X) * 2 * PI * FQ(X)
830 XL2 = L2(X) * 2 * PI * FQ(X)
REM -- Calculate Actual Mid point Z by figuring L network "backwards"
850 R2 = ((XL2 / R3) ^ 2 + 1) * R3
REM -- Capacitance of L network
860 XCL = R2 / SQR((R2 / R3) - 1)
REM -- Pi section caps
910 XC1 = R1 * XL / (R1 + SQR(R1 * R2 - XL ^ 2))
920 XC2 = R2 * XL / (R2 + SQR(R1 * R2 - XL ^ 2))
REM -- Pi-section Q
930 Q1 = (R1 + SQR(R1 * R2 - XL ^ 2)) / XL
940 Q2 = (R2 + SQR(R1 * R2 - XL ^ 2)) / XL
950 Q0 = Q1 + Q2
REM -- Combine output C of Pi-Net and L network C
960 XT2 = (XC2 * XCL) / (XC2 + XCL)
REM -- Figure C's
970 C1 = 1E+12 / (2 * PI * F * XC1)
980 C2 = 1E+12 / (2 * PI * F * XT2)
990 PRINT #1, FQ(X); TAB(10); INT(Q0 * 10 + .5) / 10; TAB(20); INT(C1); TAB(30);_
INT(L1(X) * 100) / 100; TAB(40); INT(C2); TAB(50); INT(L2(X) * 100) / 100; TAB(60); INT(R2)
995 NEXT X:
998 PRINT #1,
999 NEXT Z
1000 CLOSE
*** A Typical Output file ***
4500 ohm to 52 ohm PI-L Network
FREQ Pi-Q C1 pF L1 uH C2 pF L2 uH Mid Z
1.8 15.1 247 37.78 1794 8.07 212
2 14 202 37.78 1424 8.07 250
3.5 15.5 130 18.89 954 4.03 203
4 14 101 18.89 712 4.03 250
5.4 14 75 13.99 527 2.99 250
7.15 14 56 10.56 398 2.25 250
10 14 40 7.55 284 1.61 250
14.15 14 28 5.34 201 1.14 250
18.15 15.7 25 3.56 188 .76 197
21.2 14 19 3.56 134 .76 250
24.85 16 19 2.54 141 .54 190
28 14.6 15 2.54 109 .54 227
29.7 14 13 2.54 95 .54 250
4500 ohm to 25 ohm PI-L Network
FREQ Pi-Q C1 pF L1 uH C2 pF L2 uH Mid Z
1.8 17 261 37.78 1797 8.07 358
2 16 216 37.78 1413 8.07 436
3.5 17.3 137 18.89 958 4.03 340
4 16 108 18.89 706 4.03 436
5.4 16 80 13.99 523 2.99 436
7.15 16 60 10.56 395 2.25 436
10 16 43 7.55 282 1.61 436
14.15 16 30 5.34 199 1.14 436
18.15 17.5 27 3.56 190 .76 326
21.2 16 20 3.56 133 .76 436
24.85 17.8 20 2.54 143 .54 313
28 16.5 16 2.54 108 .54 391
29.7 16 14 2.54 95 .54 436
4500 ohm to 100 ohm PI-L Network
FREQ Pi-Q C1 pF L1 uH C2 pF L2 uH Mid Z
1.8 14.7 243 37.78 1551 8.07 183
2 13.4 198 37.78 1250 8.07 202
3.5 15.1 128 18.89 821 4.03 178
4 13.4 99 18.89 625 4.03 202
5.4 13.4 73 13.99 463 2.99 202
7.15 13.4 55 10.56 349 2.25 202
10 13.4 39 7.55 250 1.61 202
14.15 13.4 28 5.34 176 1.14 202
18.15 15.4 25 3.56 162 .76 175
21.2 13.4 18 3.56 117 .76 202
24.85 15.7 18 2.54 121 .54 172
28 14.1 14 2.54 95 .54 191
29.7 13.4 13 2.54 84 .54 202