accordingly to this textbook i have, it says that the RF signal has a tendency to travel on the surface of the conductor. This causes unexpected resistances in the conductor.
From memory Audio-G (Audio Guru, but comon Audio-G sounds cool) said that the bigger the wire the more surface area for the FR signal to travel on. And this provided better performance???
Skin effect is caused by the electrons repelling each other. This has an effect in straight conductors but tends to cancel out when they are wound into coils as the repulsion is the same at all point due to neighboring wires.
At high frequencies the current travels only along the outer of the conductor the depth the current travels into the conductor is the skin depth which is determined by the frequency.
So at high frequecies it is better to use several thinner wires twisted together, that way the curent will travel in all of the conductor (no wasted copper).
30 guage wire is awful darn small for a VHF inductor. I have never heard of using an iron core for such a high frequency.
I used 9 turns of 1mm enamelled wire tightly wound on a 3mm former. The end wires have exactly 0.4" spacing and I spaced these air-core inductors about 2mm above the board. Even though I used Veroboard, my layout was tight without any extra track lengths so my wiring was extremely short, like a pcb.
If you want to worry about skin effect?, try searching for 'litz wire'.
But! - have you EVER seen a VHF coil wound using Litz wire? - including coils in high power radio transmitters!. The only place I've ever seen Litz wire used is in old IF transformers, and old shortwave radio coils.
I used 1mm enamelled wire for the coils in my FM transmitter and they work fine. I used such a heavy wire not only for its high surface area which helps "the skin effect", but also because it allows the coils to be tightly wound. The coils are so strong that they don't change if I bump them or even if I stand on them. :lol:
Hi MS,
Oh yeah? If the power cord to your toaster had 100 ohms per cm then at 1m in length and at 120VAC it would pass a max RMS current of only 6mA! The wire would heat with 0.72W and the toaster would heat with only 0.4mW.
The toaster is probably only 12 ohms to dissipate about 1KW, and the cord is two wires each with a resistance of probably only about 0.05 ohms to dissipate about 10W. Therefore the resistance of the wires in the cord are about half a milli-ohm per cm.
But you are correct, the wire is way less than 100 ohms per cm, about 200,000 times less! :lol: