Can a wire behave like a filter? - Page 1
Forum section: electronics / beginners

author: FriedMule
author_rank: Frequent Contributor
timestamp: February 27, 2022, 01:49:28 am
content: Please forgive me, but this question has to be a bit long, I have several times experienced that my lack of knowledge and language skills, have being a cause for you wasting your time in trying to understand what I am asking about. Thanks!:-)My question is about a group of single wires (one lead with plastic around, either stranded or solid wire).In the "good old days" could you take two wires in parallel and use them as a radio or TV antenna, just by position the double wire as the letter "T", I imagine that these two parallel wires acts as a bad capacitor.You can also wind a positive and a negative wires around each other to reduce the magnetic field they create.If you wound a wire around a core, do you get the wire to act as an inductor.But can you make many wires braided together to behave like a sort of filter?Let's imagine you have 24 single wires, these gets braided together and in both ends do these wires get grouped in two, one to positive and one to the negative, would such a braided cable be able to filter out some of what is going through the cable? Let's say you try to use it as an antenna, but the signal gets "bad" because of the filtration?

author: bob91343
author_rank: Super Contributor
timestamp: February 27, 2022, 02:13:20 am
content: Yes it can be a filter. Before looking at how that could be possible, I suggest reading about transmission lines. That old book by John Kraus, called 'Antennas' is a good reference as well.

author: FriedMule
author_rank: Frequent Contributor
timestamp: February 27, 2022, 03:22:21 am
content: Thank you so much, I have a lot of reading to do, so this subject may be a couple of months in the future. :-)May I please ask you if you can give me a basic idea on how and why, does it take 24 cables?

author: bob91343
author_rank: Super Contributor
timestamp: February 27, 2022, 05:36:02 am
content: You were the one who said there are 24 cables. I don't know where you got that number.

author: jonpaul
author_rank: Super Contributor
timestamp: February 27, 2022, 10:31:10 am
content: Frequency: Audio? RF? Microwave?Legnth of the cable? Twisted pair, coax, single wire?See the excellent Belden app notes and blog of Steve LAMPEN on cable and wire transmissionJon

author: jwet
author_rank: Frequent Contributor
timestamp: March 01, 2022, 04:14:40 pm
content: I will try to delve in here but you do need to have some basic knowledge and the problem is pretty wide open. I was a beginner once and I know what it feels like to ask questions without enough knowledge to make an expert understand. It must twice as hard in a second language.Wires have inductance- this is a property of current interactions in a conductor and the magnetic field created by it. The wire doesn't have to be a coil but coils work better because they can couple to each other. The wire doesn't have to be wrapped around a core either but this will concentrate the flux and make it work better. The "self inductance of a small straight piece of hookup wire (24 AWG) wire is very approximately about 7 nH (10e-9 H) per cm (its complicated) . The reactance, roughly AC resistance, of this inductance is proportional tothe frequency applied ; X=2*pi*F*L. If you create an inductor and run signals down it, high frequencies will experience this higher resistance and low frequencies less so. This is a filter- it reacts differently to different frequencies. The more inductance, the higher the inductance and the more the reactance will be.This is a about as simple as I can explain it. Good luck.