If the impedance of the load matches that of the source, impedance matching is not required, and the balun has a 1 : 1 impedance ratio. This relation is also the case for finite transmission lines until the wave reaches the end of the line. For practical applications, please visit manufacturers’ websites and consult their data. Transmission line impedance is an important aspect of RF electronics, as it greatly influences the quality of a signal. 9)dB = 1. . in both cases, the speed and the Characteristic Impedance depend upon logarithms of the ratio of two distances in the cross. The cutoff frequency is the frequency up to which the system functions efficiently. Linkedin. 035 in), outer conductor diameter 3. 00 / each. “468” is the constant used to convert frequency in MHz to feet. where. RG-8 and RG-213 (50 ohm); and RG-11 (75 ohm) are about 0. So 50 ohm cables are intended to be used to carry power and voltage, like the. . The calculator will calculate one possible solution for a Single Stub Match that you can implement in your antenna system. The impedance of a coaxial cable is a critical parameter that characterizes its electrical properties. When the cable is loaded with plastic, the C increases, but the L does not, so speed and impedance change from those in the same size air-spaced cable. 15 mm (0. 80 for typical two-wire lines and coaxial cables. 405 inch. When a balanced source is to be isolated from an un-balanced load, the impedance matching transformer is referred to as a balun. Note that the very first dip is where the cable is less than 1/4 wavelength. εr = Dielectric constant of the insulator. R ≈ l σ(δs2πa) (δs ≪ a) The impedance of a wire of length l and radius a ≫ δs is given by Equation 4. in both cases, the speed and the Characteristic Impedance depend upon logarithms of the ratio of two distances in the cross. 854187817620. output power, and size requirements. Customers can choose to either buy cable in bulk or use our large selection of coax types to construct custom cable assemblies. RF Calculators. Maximum Operating Voltage (Vrms) 4000. 81, giving an impedance of 120. Visit to learn more about our other electrical engineering tools. × 10 −12 F/m is the. The quality of an impedance match can be expressed mathematically by the reflection coefficient (Γ). Permeability (µ) is assumed to be 1. 4w. Attenuation (dB/100 ft , @ 400 MHz). Maximum Voltage Rating (RMS) 4000 V. Because. A coax is a common transmission line construction and most rf cables are coax. There are three main classes of characteristic impedance for coaxial cables : 50 Ω, 75 Ω and 95 Ω. Transmission lines Transmission line concepts and an online transmission line calculator by Owen Duffy, VK1OD. VSWR is defined as the ratio of the maximum to minimum voltage on a loss-less transmission line (expressed as 3. 1: Determining the inductance of coaxial line. The length of a half-wavelength dipole can be calculated by the given formula: L =. Linkedin. For example, if you wish to input "25000000", just type "25M" instead. D = Inside diameter of the shield. Coax Impedance Calculation. See full list on allaboutcircuits. Zs = Ze + (R1 + R2) Z s = Z e + (R1 + R2) Where Zs is the line-earth loop impedance. A coax is a common transmission line construction and most rf cables are coax. c is the speed of light 299,792,458 m⋅s −1,. Equation. Apr 22, 2009. D (inches) d (inches) for a typical polyethylene-insulated cable. Length of the three-quarter-wave section 3λ g /4: mm. D is the inside diameter of the coax cable shield,. ) Published under the terms and conditions of the. I used 100m for l. The cable is a transmission line (read more here) and it will transport a signal properly ONLY when the input and output of the cable/transmission line is TERMINATED by the proper impedance ! So a 50 ohm coax cable needs a source with a 50 ohm output impedance and it needs a 50 ohm load at the other end of the cable. D is the inside diameter of the coax cable shield,. This is the only way to calculate the total impedance of a circuit in parallel that includes both resistance and reactance. Here is my measurement to a piece of RG6 cable. This works from DC to 1. c is the speed of light 299,792,458 m⋅s −1,. The characteristic impedance of an infinite transmission line at a given angular frequency is the ratio of the voltage and current of a pure sinusoidal wave of the same frequency travelling along the line. where. d is the diameter of the inner conductor of the coax cable; units of D and d must be the same,. The Coaxial Line Impedance (Z0) Calculator is a valuable tool for engineers working with RF and telecommunications systems. Set Parameters as Desired. Coaxial Impedance Calculator. RELATED WORKSHEETS: Characteristic Impedance Worksheet A twisted-pair cable is simply two wires that are twisted together so as to reduce radiated EMI (electromagnetic interference) and mitigate the effects of received EMI. . × 10 −12 F/m is the. 25 inches. For example, if you wish to input "25000000", just type "25M" instead. 035 in), outer conductor diameter 3. What is the characteristic impedance of twisted pair cables? 100 ohms. Where L is the length of the dipoles. D is the inside diameter of the coax cable shield,. D is the inside diameter of the coax cable shield,. Why these values? One explanation is that the value of 50 ohms was selected because a coaxial cable with polyethylene dielectric with relative permittivity ε r = 2. The characteristic impedance of a coaxial cable with a dielectric is then and the propagation velocity of a wave is, where c is the speed of light In free space, the wavelength of a wave with frequency f is For a polyethylene-insulated coaxial cable, the propagation velocity is roughly 2/3 the speed. From my memory, cable splitters (such as for splitting a cable tv coax cable into two televisions) provide impedance matching to prevent signal reflections, etc. 5 ohms. See also this excellent PDF by Audio Systems Group, which shows the impedance of a $75Omega$ coaxial cable rising to $1000Omega$ at 1 kHz, and almost $10kOmega$ at 1 Hz. Print - Advertisement - This calculator. 557 GHz. A microstrip is a type of transmission line in which a strip of a conducting material like copper is mounted on a dielectric material and routed to a ground plane. Coaxial Cable Impedance Calculator. September 8, 2022. It is horrible! At the compromise value of 50 ohms, the power has improved a little. Now we can add the resistances from the inner and outer shell since they're in series. The coax cable has a capacitance as a result of the gap between inner conductor and outer shield of the cable. From the u. Impedance mismatch of 75 Ohm Cable. Example: Calculate the distributed capacitance and inductance, impedance and a cutoff frequency of a coaxial cable RG-58 with the following characteristics: inner conductor diameter 0. Suitable for VHF (~1. This connection steps down the high antenna impedance to. If we calculate the inner and the outer impedance using formula Z=R+j (XL-XC), where. the combined velocity factor will be around 0. Now, let us investigate the physical meaning of return loss. Short the cable ends and measure the ZSC (cable short circuited). 035 in), outer conductor diameter 3. Explore the Coaxial Cable Calculator, a handy tool for calculating various parameters of coaxial cables such as impedance, capacitance, inductance, and cutoff frequency. This frequency to wavelength calculator helps you determine the wavelength of a waveform based on the frequency. This is a required field. The impedance of this antenna is around 300 Ω, so you may want to use a 4 : 1 transformer or a λ/4 long piece of 150 Ω coaxial cable to match this impedance to 75 Ω. 9 mm (0. 2 OUTPUTS: Impedance = 51. In the application, the reverse calculation is also available, finding the width and length of the strip according to the given characteristic impedance and the electrical length of the T-line. The use of a standardized impedance makes RF design much more practical and efficient. From then on the dips occur when the cable is an odd number of quarterwaves, or the distance between each dip is caused by an additional half-wave. **Note: Like our stripline impedance calculator, all of our RF calculators allow SI prefix input. Example 7. For example, in a vacuum, the velocity of propagation would be 100% or 1 (depending on how it is represented). 7mm. If you are interested in how to build a copper J-pole antenna, follow these instructions: Choose 145 MHz from the 2-meter frequency band, note the speed of light c, and calculate the wavelength λ from the formula λ = c/f = (299,792,458 m/s) / (145,000,000 1/s) = 2. d is the inner diameter of the cable. 20 to 12. . 15 mm (0. d is the diameter of the inner conductor of the coax cable; units of D and d must be the same,. The cable is a transmission line (read more here) and it will transport a signal properly ONLY when the input and output of the cable/transmission line is TERMINATED by the proper impedance ! So a 50 ohm coax cable needs a source with a 50 ohm output impedance and it needs a 50 ohm load at the other end of the cable. ABOUT US. 2. 3pF) in the tuner to 111. A coaxial cable is designed Basis of Calculation. In the amplifier design, above, the goal is to transform an output load of 50 ohms down to 12. Suitable for higher power (~1800 watts) at HF. VE2ZTT said: Most ( if not all ) receivers ( scanners ) antenna input is 50 ohm ( READ YOUR SPEC. ε0 = permittivity of free space = 8. The Smith Chart achieves this by superimposing a grid on S11 that maps load impedance. Use the frequency and layer thickness/Dk value to determine the antenna size. pr is the relative permittivity of the material the cable is made from. However, the nominal refer-ence impedance of the analyzer is 50 + j0 Ω, rather than the complex characteristic impedance of the cable. In a nut shell the characteristic impedance of a coax cable is the square root of (the per unit length inductance divide by the per unit length capacitance). 14. Now we can add the resistances from the inner and outer shell since they're in series. Cable Inductance. Coaxial Cable: A common type of coaxial cable has a characteristic impedance of 50 ohms. 0815. Cutoff Frequency of Lowest Order Mode: 6. The coaxial cable, along with the balanced two-wire, is the most common type of transmission line used in RF communications. A Coaxial cable is a type of cable that is used to make transfer RF/Microwave signals. The nice part about coax is that it can be bent and flexible unlike most pcb transmission lines. Return loss (RL) is the ratio of the reflected power to the incident power, in decibels (dB). Now, to calculate the necessary line length: assuming that our cable has a velocity factor of 0. 0:1, 2. As can be seen from the calculation results, the impedance remains at 50 Ohms with the cable fitted. The. For any cable type, it is equal to the reciprocal (1/x) of the square root of the relative permittivity of the cable’s insulation. . LOGIN. frequency: f = DC - 100Hz f = 1kHz f = 100kHz Zo: Zo = R G Zo = L C Zo = R ωC Zo. A coax loss calculator is an essential tool for network planning that helps in calculating attenuation and choosing the right coaxial cable for your network. 9 mm (0. Another way is to use ladder line. Characteristic Impedance (Zo) 75±3 ohms. It is around 30cm cable. Then use the LCR Meter and measure the inductance at the open end of the cable. I leave it to other sources to provide the complex equations needed to precisely model coaxial cables. The tool provides two networks that will have the desired impedence at that frequency, but their. 4w. お知らせ:2023年11月23日(木)~24日(金)は米国祝日のため、受注のタイミングにより通常納期より2~3営業日多く頂戴する場合があります。50 ohms is used because it is the impedance of the coaxial cable, except audiovisual applications is 75ohms, and so we avoid having to use an impedance matching circuit to connect the PCB to the outside. Pasternack RG178 flexible coax cable is 50 Ohm and has a PTFE dielectric. Example: Calculate the distributed capacitance and inductance, impedance and a cutoff frequency of a coaxial cable RG-58 with the following characteristics: inner conductor diameter 0. From then on the dips occur when the cable is an odd number of quarterwaves, or the distance between each dip is caused by an additional half-wave. f if the frequency of the RF signals. Our RF calculators and converters will provide the figures you need for your radio frequency engineering needs. Where, f c = Cut-off frequency of rectangular waveguide in GHz. Choose from 50 Ohm, 75 Ohm, 93 Ohm and 95 Ohm coaxial cables or 78 Ohm and 100 Ohm Twinax cables. Question 17. If the impedance of the load matches that of the source, impedance matching is not required, and the balun has a 1 : 1 impedance ratio. Micro Coax & Twinax Cable Specifications 20Ω Coax Cable – 26 AWG 50Ω Coax Cable – 34 AWG Ω Coax Cable – 36 AWG50 Ω Coax Cable – 38 AWG 85Ω & 100Ω Twinax Cable – 30 AWG 85 Ω & 100 Twinax Cable – 32 AWG 75Ω Coax Cable – 38 AWG 100Ω Twinax Cable – 30 AWG Board-to-Board Assemblies = Eye Speed ® Coax = Eye Speed Twinax. Compared to waveguides, microstrip is generally has a lower power handling capacity, and higher losses due to the fact that it is not enclosed. There are more than 75 different RF Coaxial Connectors that can be used in wireless systems. It has an inner copper weld wire (CW) or copper-clad steel (CCS) conductor (carrying the electrical signal), which is enclosed by an insulation layer typically made of air space Polyethylene (ASP). Gamma matching allows you to match such a dipole with a 50-ohm coaxial feeder. To find the termination resistance that matches the characteristic cable impedance, connect a 200Ω potentiometer at the cable end and tune it until no reflections occur. Where, P A = Power output of Port 2. Out of Stock Online. Polar or rectangular grids only allow direct reading of S11. The entry unit of frequency can be modified, the output wavelength is calculated in meters. Lower VSWR is always desirable for a system. 854187817620. × 10 −12 F/m is the. This online reflection coefficient calculator calculates the reflection coefficient (Γ) by entering the value of the characteristic impedance Z o (in ohms. So, if the Propagation Velocity is 70%, it means that the signal. 3. RG178B/U part number from Pasternack is a RG178 coax cable that is flexible. Schelkunoff in 1934, is a very convenient parameter for the prediction and control of EMI coupling through cable shields. S. Same-day shipping if you order in the next hours!. Step by Step Procedure The 125 ohm cable is connected at the end of a regular 50 ohm RG-213 cable. The Pi (pad) RF attenuator calculator allows you to determine the Resistor values (R1 & R2) for a Pi attenuator. Formula for Antenna Near Field & Far Field Distance Calculator. Coax Conn Rx Cable and connector impedance The characteristic impedance of a cable and its connec-tors should match the impedance of the transmitter and receiver. Where we basically use the effective area instead. Cable Capacitance (pF/ft) 23. 7 Ohm = 117 Ohm) and a. Coaxial cable characteristic impedance Calculator and formula. thus a big transmission line can have the same impedance as a small transmission line if one is scaled in proportion from the other. 035 in), outer conductor diameter 3. The input impedance of such a dipole is typically less than 50 ohms and may have a reactance. 1. Coaxial characteristic impedance calculator. For example, connecting coax cable to a dipole antenna. 85, and using a speed-of-light figure of 186,000 miles per second, the velocity of propagation will be 158,100 miles per second. Free Windows program for calculating the loss and impedance transformation. We have now proven by measurement that the LOAD Termination, Signal Generator and Coaxial Cable all have. This coaxial cable calculator determines the distributed capacitance and inductance of a coaxial cable, its impedance and cutoff frequency for a given cable geometry, and relative permittivity or velocity factor. For any cable type, it is equal to the reciprocal (1/x) of the square root of the relative permittivity of the cable’s insulation. 5 mm Coaxial Connector is designed to be relatively rugged. Picking it interactively in the 3D view and. Values range between 0. Although this sounds somewhat crude and primitive, I have watched technicians perform such an “operation” several times with very good success. The formula defining characteristic impedance may be written as follows : Theoretical formula in the case of a perfect line. for chosen frequency. 65. Scroll down to find formulas for determining attenuation, wavelength, characteristic impedance, time delay, and more. The above formula is another form of the familiar equation: Z (squared) = Zo X Zr. If we calculate the inner and the outer impedance using formula Z=R+j (XL-XC), where XL=j2pifL, and. coaxial cable. Visit to learn more about our other electrical engineering tools. … with a feeder attached to it - usually a coax cable with an impedance of 50 Ω (remember to seal the endings!); Fixings; Two high-located, obstruction-free points to plant the antenna - the dipole's length is the most crucial feature to consider; and. Question 17. RG-8 and RG-213 (50 ohm); and RG-11 (75 ohm) are about 0. 5. The parameter scale of the X and Y axis of the oscil-loscope screen are 20 ns/div and 200 mV/div. Then ta ke the potentiometer and measure itsI have a passive GNSS antenna with a 6" 1. To calculate the impedance of a coaxial cable with a diameter of 0. Here it is: For outer diameter D, inner diameter d, and eccentricity c: Z0= [60/sqrt (ER)] x acosh [ (1/2)x (D/d+d/D-4c^2/ (dxD)] We entered the equation into Excel, and sure enough, if c=0 you get the same exact impedance you get from the. e. Where, Np/Ns = Turn ratio. As we know that the definition of the return loss of a system is the ratio of incident power to. By inputting the necessary values into the. High return loss means low reflected power, so high return loss is good for a system. a = r = 0. The measure of this reflected power is called as return loss. Provides an impedance matched 50 ohm coaxial connection for two receivers when feeding signal from one active antenna, or when combining two different antennas (L. A Rectangular Waveguide is a conducting cylinder of rectangular cross-section used to guide the propagation of waves. The coaxial cable is a transmission line, designed to have a specific impedance, usually 50O, though there are other standard impedances, such as 75O. If I place a trans-match between the rig and the feed, then I'm tuning the feed line. If we look again at the example of the coaxial cable and leave it open at the end, achieving a characteristic impedance of ~377 Ω does not relate to anything about the fields. The formula for the length of the matching section is as follows: Q-Match Coax (in feet) = 246 x [velocity factor] / Frequency (MHz). You can select the unit of measurement for the coaxial cable's inner diameter,. Figure [Math Processing Error] 7. This calculator can also be used for measuring coaxial cable and will then give Relative Dielectric Constant rather than Effective Dielectric Constant. Choose from 50 Ohm, 75 Ohm, 93. All coax impedance transformersThe Twelfth-Wave Transformer is often a more convenient alternative to the more well-known quarter-wave transformer Choose Coax and calculate 1/12 λ of 50Ω coax. ε 0 = 8. Coax Impedance Calculator – EEWeb Community. In the case of coaxial cables, impedance is expressed in terms of "ohms impedance". Our RF and microwave calculators and converters will provide the figures you need for your radio frequency engineering needs. 398Ω. Some industry-standard coax cables. RF calculations and RF conversions include metric-standard, link budget, coax cable, power, attenuation, frequency and many more. Sensor Fusion Comes to RetailNext: Interview with Alexei Agretchev . where. The transmission line is terminated in a load impedance of 50 . Useful. 2. The coaxial cable's diameter conduction allows for. Here's a multi-dielectric coax calculator, contributed by Alex R. A directional coupler is a passive 4-port device used to sample a small amount of microwave power for measurement purposes. × 10 −12 F/m is the. Distributed Inductance (L') For a coaxial cable, the inductance per unit length L' in henries per meter (H/m) is defined as. 15 mm (0. . The Number that follows "WR" is the width of the waveguide opening in mils, divided by 10. Choose from 50 Ohm, 75 Ohm, 93 Ohm and 95 Ohm impedance coaxial cables or 78 Ohm and 100 Ohm impedance Twinax cables. The functionality of a coax loss calculator is straightforward, yet it provides critical information for ensuring optimal performance. 124 in), type of insulation is polyethylene with the relative permittivity of 2. In fact, striplines often make components such as band-pass filter's more accurately, with more symmetric roll-off and no lower cutoff frequency. Coaxial Impedance Calculator. To use the calculator you first need to measure the impedance (resistance + reactance(j)) of your antenna, this can be done with an antenna analyzer (i. In some cases, users require a custom impedance value. 5 mm Coaxial Connector is a widely used standardized coaxial connector type with some interesting features. Frequently, it becomes necessary to match. where. When the bend radius is exceeded it alters the characteristic impedance of the cable. In a nut shell the characteristic impedance of a coax cable is the square root of (the per unit length inductance divide by the per unit length capacitance). e. Characteristic impedance = R + jωL G + jωC− −−−−−−−√ R + j ω L G + j ω C. A rectangular waveguide is commonly used for the transport of radio frequency signals. 36Ω), the impedance is: Transformed through 25 feet of RG-8 coaxial cable to 111. The length of the cable makes no difference whatsoever in regard to the characteristic impedance. Micro Coax & Twinax Cable Specifications 20Ω Coax Cable – 26 AWG 50Ω Coax Cable – 34 AWG Ω Coax Cable – 36 AWG50 Ω Coax Cable – 38 AWG 85Ω & 100Ω Twinax Cable – 30 AWG 85 Ω & 100 Twinax Cable – 32 AWG 75Ω Coax Cable – 38 AWG 100Ω Twinax Cable – 30 AWG Board-to-Board Assemblies = Eye Speed ® Coax = Eye Speed Twinax. and Canada (866) 727-8376 International +1 (949) 261-1920Another way to measure the characteristic impedance of coax cable is to measure its inductance and capacitance per unit length; the square root of L divided by C will be in ohms (not farads or henrys) and will be equal to the characteristic impedance. This ratio represented in dB is called as Return Loss. c is the speed of light 299,792,458 m⋅s −1,. 2,210. 7 - 29. An example follows. We are bespoke cable designers and manufacturers and we struggle to hit accurate designs on Coaxial Cables. Cutoff wavelength and frequency. Although implementations vary, the wire diameter is usually about 1 mm and and the wire spacing is usually about 6 mm. 15 mm (0. Conductor DCR Nom. 86 mm] x 0. If you want to put this thing outdoors, do not use brass, as it gets brittle. DS3 & DS4 Cable. The velocity factor of a foam insulated cable depends on the production technology and varies from manufacturer to manufacturer. If there is an insulator around the wire then this. #2. 35dB. 4. The coaxial cable is so fundamental that Oliver Heaviside patented it in 1880, just a few years after Maxwell published his famous equations. One online calculator tool that seems to work well and gives expected results is Coaxial Cable Impedance Calculator. c is the speed of light 299,792,458 m⋅s −1,. 3. Zp= Input/Primary impedance. To use the calculator you first need to measure the impedance (resistance + reactance(j)) of your antenna, this can be done with an antenna analyzer (i. Return loss (RL) is the ratio of the reflected power to the incident power, in decibels (dB). A quarter wave transformer is used to match two transmission lines with different impedances. Formulas. This online microstrip impedance calculator calculates the characteristic impedance of the microstrip (Ω), W/H ratio, and effective dielectric constant (εe) by entering the value of dielectric material relative permittivity (εr), the width of. This CalcTown calculator calculates the capacitance, inductance, impedance and various other parameters related to a dual dielectric coaxial cable. Formulas. 4. This causes an impedance mismatch at each staple location resulting in micro-reflections. When the source impedance is a complex value, the magnitude of the S-matrix is not always less than or equal to 1, even for a passive device. This example is for LMR-600 which is very low. Executive Summary. Coaxial cable combiners with ferrite cores are often used to combine the output powers of power amplifiers intended for wideband applica-tions. As can be seen in the following graphs, the only time a 1:1 choke-balun accomplishes a 1:1 transformation is when it sees 50 ohms at its output. The following formula is used to calculate the cut-off frequency, lower & higher operational frequency of the rectangular waveguide. × 10 −12 F/m is the. If that transmission line is 1/4 wave long, it's called a quarter-wave transformer, and it makes whatever's at the end of it look like the conjugate impedance. This topic describes a technique for calculating the impedance of a waveguide. Altium's built in impedance calculator shows the trace impedance at 34 ohms not 50 ohms. com If it. for a typical polyethylene-insulated cable. ε = dielectric constant = ε0 * εr. Pasternack's RF Calculators and Conversions section provides engineers valuable and easy-to-use tools ranging from complex mathematical formulas to simple conversions. Z0 = Characteristic impedance. This allows the signal to remain intact and not bleed out like it would without the shield. 0815 × W × V (velocity factor of the cables). where. D is the inside diameter of the coax cable shield,. Suitable for higher power (~1800 watts) at HF. Using our own calculators which, for impedance, is based on the formula above (which is the same as the calculator in the tool section of this site) our characteristic impedance turns out about 8% - 10% higher than calculated. This cable should connect to an identical impedance. EXAMPLE: INPUTS: Outer diameter = 36 , Inner diameter = 10 , Relative permittivity =2. 6 Coaxial Line. Due to its geometry, the coaxial cable impedance requires you to know the inner wire's diameter and the outer shielding. This calculator is designed to calculate the characteristic impedance of a microstrip - a flat conductor suspended over a ground plane with a dielectric between them (see diagram below). UsefulFormulas. First one is how to calculate the impedance of an equilateral patch antenna and. In summary, the design process for the coaxial probe placement is simple: Select an operating frequency and stackup. Calculation Dielectric Outer Diameter: Inner Conductor Diameter: Result: Pasternack carries hundreds of coaxial RF cables all in-stock and available for same-day shipping worldwide. Technical. In summary, if you have a transmitter with an output impedance of 150 ohms and you want to use a cable with an impedance of 75 ohms, you need to make sure your load impedance is equal to the cable impedance. MiniVNA or MFJ-269 or similar). To calculate the impedance of a coaxial cable, we use the following formula: ext {Impedance} = frac {60 imes ln (D_2/D_1)} {sqrt {varepsilon_r}}. The example structure is a standard RG6 coaxial cable. If the antenna feedpoint is 50 ohms (such as a gamma match of a beam antenna) using 75 ohm coax as the main. Identify as much information as you can about your piece of cable prior to discussion: Characteristic impedance. Where: Zo = Characteristic impedance in ΩDistributed Inductance (L') For a coaxial cable, the inductance per unit length L' in henries per meter (H/m) is defined as. 2.