与第一种方式相比，DTH方式卫星发射功率大，可用较小的天线接收，普通家庭即可使用。

Compared with the first kind of way, DTH way satellite launch big power, can use smaller antenna, average household can use.

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在全球定位系统信号不可见的情况下，可使用伪卫星系统扩展其使用范围，全球定位系统信号发生器是其中的关键组成设备。

GPS pseudolites systems were employed to extend the availability of GPS when satellites signals were not seen. GPS signal generators were the core part of pseudolites system.

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