I have a new unused commercial bias tee for sale. http://www.teletronics.com/Accessories.html#24ghzbiastee They call it a Bias Tee/dc injector. Part 17-101 on the above page. It is in a cast-type box, female N connectors. Rated at 2.4GHz. DC connector is type normally used with wall warts. This might be what you want if you don't want to build and want guaranteed specs. ron w8gus