So, one of our reps came to me with an interesting question. He was approached by someone with a copper roof who wanted to know if welding the antenna straight to the roof would allow the whole roof to become an antenna, greatly magnifying its receiving ability.
That really sounds like a great idea at first. Copper is very conductive and a roof is a big thing. There are just… a few problems.
First of all size doesn’t matter, not like you think it does.
An antenna does its best at capturing signals when it’s an exact multiple of the wavelength of the signal. Either double the size, half the size, one quarter the size, etc. You’d have to be pretty lucky to have the roof be an exact multiple of the signals you want to pick up.
And then, there’s pitch. As in, the slope of the roof.
Antennas work well when they present a slim profile to the oncoming waves, or another way of putting this is that adding more metal doesn’t actually help. So here again, only the outer edge of the roof is going to be important here, and the sloping roof itself could affect the copper’s ability to receive signal.
Finally, there’s the issue of oxidation.
As anyone who’s looked at the Statue of Liberty knows, copper oxidizes. It starts out a nice shiny brown color and as it oxidizes, a layer of green forms. This green layer doesn’t conduct electricity anywhere near as well as the shiny brown stuff so even if this worked initially it would get worse almost instantly. On the other hand, most outdoor antennas are made of aluminum which actually doesn’t have a problem when it oxidizes. The black dust on the antenna is just as conductive as plain aluminum and actually protects the rest of the antenna from damage.
So, as much as it would seem like a lot of fun and a great project to weld an antenna to a copper roof, the odds are overwhelmingly against it actually making for better reception. If you are concerned about reception in fringe areas, you can combine multiple antennas or potentially use an amplifier. Using a roof as an antenna isn’t going to do a lot for you.