We describe an impulse-radio ultra-wideband (IR-UWB) transmitter made with off-the-shelf discrete components. It was initially designed to be used in a UWB testbed for measurement and algorithm validation purposes. There already exist several versions of an IR-UWB transmitter, but many of them are made with custom designed integrated chips. For this reason, it is very difficult for anyone other than their designers to test and measure with the same material. We describe all the information the readers would need to build their own IR-UWB transmitter.