FAQ -- WiMAX -- comments on external antennas

I am occasionally asked questions about external antennas. The following comments may be helpful:

(1) vivid's modems are not designed to be used with external antennas, so YES, if you do modify the modem to add an antenna you will void your warranty

(2) modifying the modem will break its "type approval", so this is technically illegal and can get you in trouble with ACMA (see below)

(3) some high-mounted external antennas are getting signals from distant sites on the same frequency. Even though the CINR R3 metric is great (in the 30's because it was planned for separation), the R1 metric which is relevant for choosing a good DL and UL modulation is poor. In such cases the user would have been better off with a low-mounted antenna

(4) high-mounted external antennas may contribute to uplink interference at the distant site. In some recent cases ACMA have been called in and devices have been recalled.

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