Determine a cable core diameter for RF current carrying loop

Thread Starter

Bhushan Pawar

Joined Jun 5, 2017
1
Problem Statement: I wish to make a current carring cable loop to generate a controlled magnetic field. http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/curloo.html

As I understand, the magnetic field generated depends on the Current in the loop and Loop radius (Fixed). I wish to maintain the current in the 50ohm loop to 25.3mA and 8mA respectively (ie. we have voltage of 1.26V equivalent to 12-13dBm and 0.4V equivalent to 2-3dBm).

I have a signal generator which can only support max RF output level of 13dBm.

I wish to have a cable diameter as large as possible so that the resonance frequency of the loop is higher. The operating frequency is below 7MHz.

As I understand the choosing a cable with higher cross section reduces the resistance and increases the power consumption. How can I determine the maximum cable core diameter (ie. thicker cable) for the loop cable so that I can maintain specified current levels in the loop with existing signal generator?
 

GopherT

Joined Nov 23, 2012
7,983
Problem Statement: I wish to make a current carring cable loop to generate a controlled magnetic field. http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/curloo.html

As I understand, the magnetic field generated depends on the Current in the loop and Loop radius (Fixed). I wish to maintain the current in the 50ohm loop to 25.3mA and 8mA respectively (ie. we have voltage of 1.26V equivalent to 12-13dBm and 0.4V equivalent to 2-3dBm).

I have a signal generator which can only support max RF output level of 13dBm.

I wish to have a cable diameter as large as possible so that the resonance frequency of the loop is higher. The operating frequency is below 7MHz.

As I understand the choosing a cable with higher cross section reduces the resistance and increases the power consumption. How can I determine the maximum cable core diameter (ie. thicker cable) for the loop cable so that I can maintain specified current levels in the loop with existing signal generator?

The two aspects you are missing are, 1, skin effect. That is, higher frequency signals conduct only on the skin/surface of copper wires. There are well-published equations and charts. To make sure the conduction is using all of the copper cross-section, stranded wire may be best (will be best) for your application. Even each strand insulated may be best (lite wire).

Second, you are correct that diameter and current are factors in the strength of the field but number of turns and length of your coil are also factors.
 

BR-549

Joined Sep 22, 2013
4,936
The link shows a wire for the loop. What do you mean when you say cable?
 
Top