rf_engineer
join:2003-08-04
USA
| "the court maintained their right to allow unlicensed devices to interfere with licensed spectrum"
This applies when the BPL carrier attenuates their signal 20 dB below the emission limit for signals below 30 Mhz, and 10 dB below the limit for systems above 30 Mhz.
Here's the language in Title 47 Part 15.611(c):
(i) For frequencies below 30 MHz, when a notch filter is used to avoid interference to a specific frequency band, the Access BPL system shall be capable of attenuating emissions within that band to a level at least 20 dB below the applicable part 15 limits.
(ii) For frequencies above 30 MHz, when a notch filter is used to avoid interference to a specific frequency band, the Access BPL system shall be capable of attenuating emissions within that band to a level at least 10 dB below the applicable part 15 limits.
(iii) At locations where an Access BPL operator attenuates radiated emissions from its operations in accordance with the above required capabilities, we will not require that operator to take further actions to resolve complaints of harmful interference to mobile operations.
Paragraph (iii) is the problem. The level of emissions at the limits can easily cause interference; the limits were never set to entirely prevent interference, just provide a reasonable target for consumer electronics. The FCC has acknowledged this before, and the limits in the US are looser than European ones. 10 dB and 20 dB below the limit is better, but still can cause problems. The FCC is basically telling the carriers that they can emit whatever they want 10 or 20 dB below the emissions limit and the harmful interference clause is null and void. It's a bad situation as the whole basis for unlicensed operation of any device has been no harmful interference to licensed devices. |
