Small WiEx cellular phone repeater solves large problem

It seems once again that the misfortune of a Portelligent teardown analyst translates into fodder for the knife. As with an earlier Under The Hood column ab0ut a failed tire-pressure monitor scavenged from a staff member's car, the WiEx YX-510-PCS-CEL dual-band CDMA cellular phone repeater analyzed here comes by way of a lightning strike. In this case, the unit was in-use to address poor reception on a property well outside the city reaches, but a welcomed rainstorm (we've had drought conditions here in Central Texas) also brought a bolt that fried the repeater, or at least the antenna and power supply. Of course, the first response to any death in the electronic family around here is "take it apart!"

High bars in low places

Wireless repeaters address a fairly durable problem--getting a reliably strong cell phone signal in the face of many potential connectivity-killing effects. Network coverage in dense areas can be iffy at times, even with good regional tower density. Destructive multipath interference can lead to "dead spots," and sometimes building materials and construction alone are enough to dramatically attenuate signals that are fine just outside. Perhaps a more common issue is that which was faced here--a rural setting, low tower density, and a bit of topography occluding line-of-sight with the only tower around. Our analyst, having made the plunge to go without a land-line and rely strictly on a mobile phone, installed the WiEx to gain a reliable cellular-only service, and by most accounts the unit worked very well. No-bar or one-bar signal strength was indeed brought up to a solid four-bar level with improved call reliability.

In the case of the WiEx, the other challenging dimension lies in identifying design details in a fairly discrete RF circuit implementation.

All repeaters operate on the same basic principle; bring in a weak signal from the outside, boost it up for the local receiver, and correspondingly transmit handset signals back with better reach than possible from handset alone. In short, think bidirectional amplifier with antennas at each end, one to transceive with the handset, the other with the base station. In perfect form at least the effect is like parking yourself much nearer the cellular tower; call quality is improved. As an important side-benefit, the handset should be operating with lower power than would be needed when "shouting out" to operate directly with a far-away tower.