Showing posts from May, 2010

900 Mhz Experiment (Con’t)

  900 Mhz Experiment (Con’t) Filed in 900Mhz on May.02, 2010 Once the Cordless phone part of the project was complete, we went on the the cellphone interface.  I bought a device called a “Cell Phone Docking Adaptor”.  Its purpose is to link a cell phone to a normal landline telephone system.  This is the XLink BT box.  It connects to up to 3 cellphones (for three lines) and one landline phone.  It is not designed to hook to a system that is still connected to a live phone line.   It has a power connection, and a phone line output connection.  In addition, there is a USB port that is only used for applying updates (like for new models of phones).  The cellphone connection is via Bluetooth only.  No cable needed there.   When you press a button on top for one of the lines, the XLink searches for a Bluetooth signal.  You set up your phone to accept the connection.   And once you accept the connection, you just set down the cellphone nearby the XLink box, and use the phone at

900Mhz Experiment

  900Mhz Experiment Filed in 900Mhz on May.02, 2010 I happened to have an old 902 – 926 Mhz cordless phone laying around the shack. Since this is in the range of the 33cm ham band (902 -928 mhz), I thought it might be cool to make a sort of portable autopatch with it.  It has full duplex capabilities, with the base transmitting in the 902 mhz region, and the handset transmitting in the 926mhz region.  Both use narrow band FM. Here is what the end result looks like: Basic system for testing The idea of the project is to use a cellphone as the phone carrier end, and the 900 mhz cordess phone as the remote radio end. The first step was to range test the 900 mhz cordless phone.  Since this had to be outside, where there was little interference from walls, I had to devise a scheme to provide telephone carrier current in order to test it without actually hooking it to a phone line.  By putting a 9-volt battery in series with a 220-ohm resistor, all in series with one leg of t