If natural oxidation occurs at joints of electrical parts that's a bad thing (increased contact resistance)tech99 said:
I'm not aware of any antennas that use bare copper. Bare metal is usually aluminum or other metal that is fairly stable when exposed to the weather.Tom.G said:
I constructed a three element vertical out of 3/4" copper tubing and used it for years on 80m-10m. It worked great at 100w with no degradation in swr...plenty of dx with excellent signal reports. Oxidation was a non issue.berkeman said:
Seems to me you don't understand the effect good enough and the question is answerable . If the surface of Cu wire gets covered by thin coating of a poorly conducting material the RF current still mostly passes thru the thin section of an unaltered copper beneath the coating. IOW, negligible influence. Only in the case of a VERY thin wire when coating thickness starts to dominate Cu thickness the effect isn't smallJackson Richter said:
Interesting! Did you use Cu pipe just because you had it left over from a home plumbing project? I've seen a fair number of 80m-10m antennas at our local Field Day events, and I don't remember any made out of Cu tubing...Fred Wright said:
Yeah, copper heavy, alu lightberkeman said:
I found the design somewhere... in an old 60s edition of CQ magazine..I think. I decided to try it out and was amazed at the results.berkeman said:
73!Fred Wright said:
You should consider humidity of the atmosphere as a variable. The thickness of the surface dielectric oxide layer determines the velocity factor on the wire, but that effect is small because the layer thickness is small. With time the oxide may be converted to a copper acetate which has more stable but different dielectric and hygroscopic properties as it matures over time.Jackson Richter said:
Yes, copper oxide is a semiconductor, but that is not important. It is only when a connection is made that pinches, but does not cut through the surface layer, that any harmonic generation can occur. Zinc oxide is also a semiconductor, so the same is true of galvanised and zinc flashed conductors.Jackson Richter said:
Antenna efficiency will not be affected by the oxide. Much greater losses arise due to variation in height, or distance from support structures. Failure to taper the effective wire diameter to maintain constant transmission line impedance along the wire causes much greater losses due to progressive reflection. Tapered cage dipoles are often needed to make efficient HF antennas.Jackson Richter said:
Any loss is a loss, is a truism, unless it is a directional gain reduction which is not a real loss.Jackson Richter said:
Resistive I²R losses convert RF energy to heat. Reactive variations reflect energy and redistribute the phase of the signal current on the antenna. As a result of the redistribution, the gain of the radiation pattern is changed, and the expected peaks are often reduced, which some incorrectly interpret as a resistive energy loss.Jackson Richter said:
Metal oxide rectifiers were used from the 1920s.Svein said:
The electrical RF conductivity of copper oxide refers to the ability of copper oxide to conduct radio frequency (RF) electrical current. It is measured in Siemens per meter (S/m) and is dependent on factors such as the purity and crystal structure of the copper oxide.
Copper oxide has a relatively high electrical RF conductivity compared to other materials. It is not as conductive as copper, but it is more conductive than most insulating materials. This makes it a useful material for applications that require moderate RF conductivity.
The electrical RF conductivity of copper oxide can be affected by several factors, including the purity of the material, the crystal structure, the temperature, and the frequency of the RF current. Impurities and defects in the crystal structure can decrease the conductivity, while higher temperatures and lower frequencies can increase it.
The electrical RF conductivity of copper oxide is typically measured using a technique called four-point probe conductivity measurement. This involves passing an RF current through the material and measuring the voltage drop across four evenly spaced points. The conductivity can then be calculated using Ohm's law.
Copper oxide with high electrical RF conductivity has various applications, including in electrical circuits, antennas, and telecommunications equipment. It is also used in sensors, electronic devices, and in the production of conductive coatings and paints. Additionally, copper oxide is being researched for its potential use in advanced technologies such as quantum computing and solar cells.