Good News for US Amateurs on BPL Interference.

This week Motorola announced the development of a new BPL delivery method which it claims greatly reduces the potential interference to amateur radio stations.

The ARRL, which cooperated with Motorola from the start in the development of the system, reports that the semiconductor manufacturer was `all ears’ when it came to avoiding interference to radio amateurs. Quite a coup, and a slap in the face to other BPL technology suppliers who are still pushing their polluting technology in the face of mounting opposition.

Named “Powerline LV”, the new system is quite different from current North American BPL systems, as it only uses the local low voltage power line from the transformer to the home to deliver the BPL signal, using a “Homeplug” type format. The long haul distribution of the BPL signal which was previously achieved using the medium voltage power lines, is now achieved in the Motorola system by wireless. The long haul medium voltage distribution of BPL was found to be the major radiating component in US trials.

Using BPL only from the transformer to the home allows the BPL signal to be injected at much lower power, so unwanted radiation is reduced considerably. Motorola have also included proper RF level “hard” filtering for amateur frequencies at both the transformer injection point and the in-home modem.

However the Australian and New Zealand power distribution systems are very different from the North American system power distribution system.

Because the American mains power is 110V the medium voltage to low voltage transformer can only serve a few homes, and the line length from the transformer to each home must be short to avoid excessive voltage drop. In Australia and New Zealand, our 240V distribution system allows more users to be connected to each transformer and therefore a greater distance from the transformer to the home, typically one transformer every few hundred meters.

If the Motorola BPL system was used in Australia and New Zealand, unacceptably high levels of interference to HF users might still occur due to the increased length of line carrying the BPL signal into the home, and the likely necessity for higher injected power to enable the BPL signal to span that greater distance. The characteristics of such a BPL distribution system may not be very different from what we have already experienced in Australian trials where the BPL signal has been injected from a long haul fiber optic distribution feed into the local 240V power cables.

Inclusion of “hard” filters in the equipment is a major step forward in reducing interference potential, however due to the high reliance on HF usage in this part of the world, filters may need to be installed for a number of HF communications services and shortwave broadcasting, not just for radio amateurs, possibly causing lack of sufficient bandwidth for the BPL signal.

In short it’s great that the ARRL have been able to work with a company such as Motorola, and it’s testament to Motorola’s commitment to get it right, however we need to look at this technology very carefully in the Australasian context before we get too excited about it down here, but certainly it’s on the right path and a welcome step forward in anyone’s language.

The ARRL news release is available via the following Link

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