Texas Instruments 2000 LF Series, Примечание к применению

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Lit Number: 11-06-21-068
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4.5 Antenna Tails
The antenna tail serves only to allow the antenna loop to be separated from the RF
module and the longer the tail, the greater the losses that are introduced. For every
metre length of the tail, approximately 0.5 µH inductance is added. If we assume that
the standard antenna has an inductance of 27 µH and the upper limit that is allowed
with the on-board capacitance/ variable inductance is 28.5 µH, then we can add
around 3 m of extra wire and still tune to resonance.
Unfortunately, adding the extra tail also adds extra resistance and we have seen how
as the R increases, the Q drops. To minimize the added resistance, the recommended
wire for this tail is twin 2.5 mm
2
‘Jumbo’ speaker cable.
Caution
An unshielded antenna tail can pick up noise – the longer the tail, the
more potential for noise. Do not run the tail with other cables, especially
power cables.
4.5.1 Tail Construction
Of the other points about the tail we need to pay attention to when designing our own
antennas, the most important is to keep the two conductors tight together.
Figure 25. Antenna Tail Construction