Mt. Whitney Portal Store & Hostel Forums General Mt. Whitney Portal Store Message Board Cell Phone as Personal Locator Beacon?

Just a wild idea here. Has there been any thought by the authorities related to SAR to get a special portable receiver so that they could pick up a transmission from a cell phone directly without it having to go through a cell phone tower? Thus a person in trouble could communicate with SAR that is trying to find them and the signal could be used to locate them, if they aren't within range of a cell phone tower.

There are systems sold to law enforcement to provide the capability to listen to operating cellular networks, but this is not the situation with a single cell phone ie no base station to cell phone commands are being passed. These systems also can be sizable.

http://www.cellularintercept.com/pc-12-1-cellular-intercept-tdmaamps.aspx

What would be needed is a portable base station functionality and a cell phone to enable searchers to talk to a cell phone. And the base station must match the type of service used by the cell phone. There may be portable test equipment that includes the base station functionality. A first trivial Google didn't find any, but there were 106,000 hits and there were several of those that I didn't read.

This isn't a functionality that is useful until a search has already been triggered since the link won't exist until the portable base has been brought near line of sight with the cell phone point of contact.

Dale B. Dalrymple
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C'mon! Get off the couch!

Dale, Thanks for the link about the Cellular Intercept devices. From what I read there, it looks like they are about the size of a suitcase, and there are three different types, depending on the type of cell phone that is monitored.

As you mentioned, this could only be useful after a search has been triggered. Seems like almost all searches today are of this type since most people don't take PLBs along. Maybe these Cellular Intercept devices could be useful in such a search? For example, they could be used in a helicopter while searching?

Bob

The problem with the intercept devices is that they don't do enough. A cell phone begins a call by asking the base station for a channel assignment to send and receive on. If no base station responds to the cell phone, no attempt is made to transmit or receive a call. The 'bars' rating signal strength on a cell phone are a measurement of the base station control channel signal strength. The intercept devices are designed to be used where there already is functioning cellular service. You need the base station function to tell the cell phone it can make a call and what channel to use. Even if you have an intercept function and a base station function in a helicopter, the people on the ground will need to be trying to make a phone call in an area where their cell phone has told them there is no reception. How do people know when to play "Can you hear me now?" The searchers could use the link, but the searchee won't know. Until the helicopter gets close enough, the cell phones will be saying: "No Service".

There are conceivable circumstances where cell phones could be a part of a search link, but they require special equipment and special training for those on the ground.

Dale B. Dalrymple