Lars Thrane iridium LT-3100S, Руководство пользователя и инструкция по установке

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LT-3100S GMDSS User & Installation Manual Rev. 1.02 Interfaces
Lars Thrane A/S www.thrane.eu Page 27 of 71
In Figure 29 two different input voltages (12 VDC and 24 VDC) illustrate the maximum length of the coaxial
cable as a function of the DC cable resistance.
NOTE : The DC cable resistance that is illustrated in Figure 29 and used to calculate the maximum
cable length is the sum of the DC inner conductor resistance and the DC outer conductor
resistance. Some data sheets are not providing sufficient information about the DC
resistance, in which cases, the cable manufacture must be approached to obtain this
information.
Lars Thrane A/S has calculated the maximum allowed cable lengths with two coaxial cables as illustrated in
Table 6. The two cables are FF195LSFROH (~RG-58) and FF400LSFROH (~RG-214).
The cable lengths calculated in Table 6 are obtained by reducing the input voltage by 10% (10.8 VDC and
21.6 VDC) to compensate for variation in the power source.
The total DC resistance for the two cables are:
IMPORTANT : If using a coaxial cable that is different to what is specified in this section (FF195LSFROH
and FF400LSFROH), then verify that the coaxial cable maximum signal loss (listed in Table 5)
is respected and calculate the maximum cable length as a function of the input voltage and
the total DC resistance. Contact Lars Thrane A/S to get assistance on selection and
acceptance of a specific coaxial cable.
NOTE : The LT-3110S Control Unit must be powered off when connecting or disconnecting the LT-
3130 Antenna Unit.
Cable Type 12 VDC Supply
Max Cable Length
24 VDC Supply
Max Cable Length
FF195LSFROH (4.9mm) 70 m 285 m
FF400LSFROH (10.3mm) 265 m 500 m
Table 6: Maximum coaxial cable length to be used on 12 VDC and 24 VDC (cable examples).
Cable Type Inner Conductor DC
Resistance [ Ω /km]
Outer Conductor DC
Resistance [ Ω /km]
Total DC Resistance
[ Ω /km]
FF195LSFROH (4.9mm) 24.9 15.8 40.7
FF400LSFROH (10.3mm) 4.5 6.5 11
Table 7: Total DC resistance (cable examples).