A couple of weeks ago I came across the article, Combine power feed and data link via cable for remote peripherals, in an email newsletter from EE Times. While this article shows you how to power remote peripherals via the signal lines used to connect them to a computer, this technique can also be used in an amateur radio station to power say a remote antenna tuner via your coax feedline.
You can, in fact, already buy such devices. MFJ, for example, sells the MFJ-4116 Bias Tee. You can make one for a lot less than the $25 a pop that MFJ wants for one, though. As you can see from the article, the circuit is simply a capacitor and an RF choke. Even with a box, a couple of SO-239s, and a power connector, you can build this for less than ten bucks each.
Another fine article on this topic was written by Jim, K5LAD. To house his circuit, he chose an electrical junction box from Home Depot. The nice thing about using these junction boxes is that they have flanges for mounting the device at both the shack and remote ends.
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