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One External Antenna and Two Wattwatchers Devices

by Darius Salgo
posted on Monday, May 28th, 2018

Jon Keeble: Chief Technology Officer

In some 3G Auditor installations, where there is very low 3G signal, locating the antenna outside a metal box can make the difference between getting a signal or not.

There are two ways to arrange things so that the antenna is outside the metal meter box

  • Install an IP66 plastic enclosure outside and next to the metal box and use it for the Auditor and antenna
  • Mount the Auditor inside the metal box, and use a cable to locate the antenna outside the box.

If there are two Auditors, two external antennas can be used. However, if the antennas are too close together they may not function very well. What is “too close” … can’t say! my guess, keep them as far apart as possible, and greater than two times their length.

Another method is to use a “2-way resistive hybrid combiner”. These things have a minimum loss of 6dB (that’s about 2 or 3 RSSI points). The actual loss is pretty much 6dB plus a negligible amount.

They are made of conductive material so will have to be mounted securely to the inside of the metal meter box so that they cannot come in contact with any live metal.

The 6dB loss is offset by having the antenna outside the box (+12dB) plus the antenna gain (+5dB), so the net result is about +11dB (about 4 RSSI counts, a very useful amount).

The use of such a device makes effective use of a single long (hi gain) antenna.