Lit Number: 11-06-21-068
Page (20)
Note:
The values in this table are calculated and because of component
tolerances, may not be exactly right for a particular reader.
The values in Table 2 assume that high voltage (1000 ~ 2000 VDC) polypropylene
capacitors are used. When high Q antennas are in use be careful not to exceed the
manufacturer’s ratings for these capacitors, because as frequency increases the AC
voltage capability of these capacitors reduces.
Figure 23. Polypropylene Capacitor De-rating
When designing an antenna that has to be a set size and by varying the number of
turns, the antenna can have an inductance too low or too high, always opt for ‘too low’.
From Table 2, if the inductance is just too high e.g. 30 µH, a 0.47µF capacitor in series
is required. If the inductance is just too low e.g. 22.5 µH, a 0.010 µF capacitor in
parallel can be used. The smaller capacitor is 10 times less expensive and much
easier to fit in parallel across the antenna terminals
Figure 24. Polypropylene capacitors (0.01 µF & 0.47 µF)
1000
10,000
100,000
1,000,000
20
40
60
100
200
300
500
700
Hz
V.eff (~)
2000 VDC/ 500 VAC
1500 pF
4700 pF
0.022 µF
1000
10,000
100,000
1,000,000
20
40
60
100
200
300
500
700
Hz
V.eff (~)
2000 VDC/ 500 VAC
1000
10,000
100,000
1,000,000
20
40
60
100
200
300
500
700
Hz
V.eff (~)
2000 VDC/ 500 VAC
1500 pF
4700 pF
0.022 µF
134.2 kHz
134.2 kHz
Summary of Contents for 2000 LF Series
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