Embedded Files
The inductance of the full wave wire equivalent, the lumped component radiator element, equates to an inductance at the lowest frequency of operation of a value of:
full wave length * inductance of wire per metre : (300 / 1MHz) * 300nH = 300uH of inductance as a coil of wire.
The impedance match tuning of the 50Ω stub tuning are as follows with the calculated SWR matching values.
The code for the base 50ohm stub circuit loading impedance is listed below as a BBC Basic code file in a text window.
Text Box
10 Cshunt= 120E-12
20 Lcoil = 3.5E-6
30 PRINT
100 PRINT
110 PRINT TAB(15);"HF vertical antenna stub tuning Trapped"
120 PRINT TAB(15);"Cshunt = ";Cshunt/1E-12;"pF";" Lcoil = ";Lcoil/1E-6;"nH "
130 REM PRINT TAB(15);"leg_B = ";segments_B;"m"
140 PRINT
150 PRINT TAB(15);"performance spec's"
160 PRINT
170
180
190
200 FOR f = 1 TO 30 STEP 1
210 PROC_sums
220 NEXT
230 PRINT
240
250 REM *CHDIR C:\Users\alastair\Pictures\antenna designs
260 REM *SCREENSAVE 50omh_mobile_phone_antenna.bmp 1,1,2000,1100
270
280 END
290
300
310
320 DEFPROC_sums
330 Xc=1/(2*PI*f*1E6*Cshunt)
340 Xl = (2*PI*f*1E6*Lcoil)
350
360 Trap_effect = ((Xc*Xl)/(Xc+Xl))
370
380 L_trap_effect_inductance = Trap_effect / (2*PI*f*1E6)
390
400 L_antenna_inductance = L_trap_effect_inductance
410
420 resonant_length = L_trap_effect_inductance/(0.3E-6)
430
440 wave_length = L_trap_effect_inductance * 2 * PI * f * 1E6
450
460 SWR_imped = (wave_length)/50
470
480 PRINT TAB(15);" freq = ";f;"MHz";TAB(32)"eqiv. stub = ";INT(resonant_length * 100)/100;" m";TAB(59);"coax line = ";INT(50*SWR_imped*10)/10;" ohms";TAB(88);" SWR = ";INT(SWR_imped * 100)/100
490
500 ENDPROC
510
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