Copper tube or aluminum tube ?
The losses of an aluminum radiator can be 4db worse compared to a copper radiator of the same thickness. Stainless steel is even worse.
After calculations using loopcalc.exe :
For the same efficiency, an aluminum radiator should have 2.5x more thickness
than an equivalent copper radiator has.
|=||Costs for copper and aluminum tubes differ therefore little.|
|=||Copper and aluminum must both be painted, as bare aluminum oxidizes too.|
|_||Bending aluminum tube into a circle is a specialists task and very expensive.|
|_||The welding of aluminum causes :
extra transport costs of the completed loop to the antenna site,
impossible moving through housing.
|+||Brass knees + tin solder, cost less than the argon welding of aluminum.|
|+||Copper tubing can be cheaply soldered yourselves for free, using tin
on the definitive antenna site itself.
|+||Separate 2.5m long copper tubes can be costless transported in you
and easily moved through buildings.
|+||The thinner copper tubing is less obvious than bigger aluminum tubing.|
Construction with copper is much easier, and
extra costs are much lower.
Think about thick Cellflex coax.