The inductance of this structure is of interest for a number of reasons – in particular, for determining the characteristic impedance of coaxial transmission line, as addressed in Section 3. Engineers were designing air-filled coaxial cables for radio transmitters designed to output kW worth of power. The coaxial cables generally fall into three main classes; 50. R = l σA R = l σ A. More consistent results will usually be obtained by using a dedicated cable joiner or a plug and socket with the same impedance as the cable. CCTV & Security Cable. The coaxial cable is a transmission line, designed to have a specific impedance, usually 50O, though there are other standard impedances, such as 75O. The quality of an impedance match can be expressed mathematically by the reflection coefficient (Γ). Apr 22, 2009. where. Note that these calculations are theoretical and engineers and technicians will probably never have the. The choke balun usually does the same thing as a regular 1:1 current balun but adds the high impedance path to the common mode currents too. EXAMPLE: INPUTS: Outer diameter = 36 , Inner diameter = 10 , Relative permittivity =2. 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. It is recommended not to operate RF Connectors above their max. Geometriy is not that critical. S. CST Cable Studio generates equivalent circuits from the cable harness based on classical transmission line theory. Identify as much information as you can about your piece of cable prior to discussion: Characteristic impedance. . This is a required field. Zs = Ze + (R1 + R2) Z s = Z e + (R1 + R2) Where Zs is the line-earth loop impedance. in both cases, the speed and the Characteristic Impedance depend upon logarithms of the ratio of two distances in the cross. You can calculate it with the following equation: Z (z) = V (z)/I (z). The above formula is another form of the familiar equation: Z (squared) = Zo X Zr. Wireless Converters and Calculators. 854187817620. It matters (used to matter) to telephone. c is the speed of light 299,792,458 m⋅s −1,. The capacitance of a one conductor shielded cable is given by the formula below: Where: C = Total capacitance of the cable (microfarads) I charge = Charging current of the cable. d is the diameter of the inner conductor of the coax cable; units of D and d must be the same,. Cutoff Frequency of Lowest Order Mode: 6. Polar or rectangular grids only allow direct reading of S11. For Example WR-650 means a waveguide whose cross section width is 6500 mils. Since we might as well find the impedance per length, we can study the expression: Rl = 1 σA R l = 1 σ A. 5. The coax is a good way to create a transmission line. Figure 3. Outer diameter of the co-axial cable (D) Inner. MiniVNA or MFJ-269 or similar). 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. R = Zo (K + 1/K) Where, K2 = P3 / P2; (P3 - power at port 3) (P2 - power at port 2). These two cables will transform the impedance for maximal power transfer. 125 MHz. 4w to achieve 100w at the aerial. 240 DIA) Solid Copper center conductor Foam Polyethylene Dielectric Aluminum Tape outer conductorBoth of the cables are inside a bigger one: The black part is the isolation. Any change of L/C when passing through connectors results in a reflection of energy from the mismatch. Email. Executive Summary. South East Ontario. f if the frequency of the RF signals. This tool is designed to calculate the inductance of a coaxial cable if its dimensions are provided. 5dB loss per 100 feet at 146 MHz). The calculator will calculate one possible solution for a Single Stub Match that you can implement in your antenna system. The area just becomes the effective area, so for the inner shell, 2πaδ 2 π. Maximum Operating Voltage (Vrms) 4000. f 1 = Lower operational frequency in GHz. In the limiting case of infinite load impedance, the Because a coax operates in TEM mode — with the electric and magnetic fields normal to the direction of propagation along the cable — modeling a 2D cross section suffices to compute the fields and the impedance. Location. 4. After all, if there is a mismatch of the antenna with this cable, the signal will be reflected before it enters to the cable. Characteristic Impedance Calculation For Typical RG58U Coaxial Cable The plots below show the characteristic impedance Zo for a coaxial cable with typical RG58U characteristics (cables from different manufacturers differ somewhat in the exact physical dimensions, dielectric constants etc. A commonly-encountered form of parallel wire transmission line is 300 Ω 300 Ω twin-lead. Visit to learn more about our other electrical engineering tools. 191Ω. Early in my explorations of electricity, I came across a length of coaxial cable with a label of “50 ohms” printed along its outer sheath (Figure below). It is widely used for data communications and telecommunications applications in structured cabling systems. This is the online directional coupler calculator that calculates the coupling (dB), coupling loss(dB), insertion loss (dB), and directivity (dB) of a directional coupler by entering the value of input power P1 (dBm/Watt(s)), output power. Formulas. Coax Impedance (Transmission Line) Calculator. diameter Schedule 40 PVC form. Telegram. Resistance in this calculator formula for pi attenuator is measured in Ohms. If a short section of a 50 ohm cable has a 75 ohm impedance, then 33% of the voltage signal will be reflected at each end of the 75. Throughout this document the shorter term cable impedance may be used. æ k s /), is a type of electrical cable consisting of an inner conductor surrounded by a concentric conducting shield, with the two separated by a dielectric (insulating material); many coaxial cables also have a protective outer sheath or jacket. Frequently, it becomes necessary to match. 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. frequency: f = DC - 100Hz f = 1kHz f = 100kHz Zo: Zo = R G Zo = L C Zo = R ωC Zo. In the case of an ideal microstrip, where one of the conductors is infinitely. This is a required field. A coax is a common transmission line construction and most rf cables are coax. 345 IMT Conduit 1. 1 7. 66 and 0. 854187817620. VSWR Conversion Table. Cut-off Frequency (fc) GHz. The twisted pair helps create a more uniform inductance and capacitance per unit length of wire to ensure a constant impedance, by keeping the return path as close to the signal as possible. Facebook. where. Coax Inductance Description. G = 2πσ ln(b / a) Figure 2. Lower VSWR means lower reflection power (good impedance matching); thus, power transfers to load will be high. Transmission line impedance is an important aspect of RF electronics, as it greatly influences the quality of a signal. 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. d is the diameter of the inner conductor of the coax cable; units of D and d must be the same,. 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. 850c-0. RF Calculators. 0:1, 2. Over time properties of standard coaxial type cables have been standardized. 04 feet = (246 x . Just look at the power handling at 60 ohms - below 50%. 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. Cable Capacitance (pF/ft) 23. it has double shielding, outer layer is stranded/woven wires, inner layer is metal strip wrapped in spiral, PTFE look alike. 11. Get. VSWR (Voltage Standing Wave Ratio) and Return Loss both measure the same parameter i. R = l σA R = l σ A. Grover, Dover Publications, 2004 . A cable can be modelled with KVL using 0 Ohms or some small DC resistance for all frequencies from DC to about 1/10th of a wavelength of the cable length and also at 1/2 wavelength and all. The cable input. “Inductance Calculations” , F. 8542*10^ (-12). L = Series inductance per unit length. 3pF) in the tuner to 111. is required to do the impedance transformation from 50 ohms to 292 ohms at 146 MHz. Kenneth L. 2 OUTPUTS: Impedance = 51. 15 mm (0. 1. Coaxial Cable Calculator. Distributed Inductance (L') For a coaxial cable, the inductance per unit length L' in henries per meter (H/m) is defined as. High return loss means low reflected power, so high return loss is good for a system. Conductor DCR Nom. RG6 Coaxial Cable in Black. While commonly constructed using printed circuit boards, this structure can also be built using other materials as long as there is a conductor separated from. Example. Pasternack’s Coaxial Cable Impedance Calculator allows you to enter the Outer Diameter Dielectric width, Inner onductor Diameter width and either the Dielectric. **Note: Like our stripline impedance calculator, all of our RF calculators allow SI prefix input. for chosen frequency. 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. The. Gamma matching allows you to match such a dipole with a 50-ohm coaxial feeder. Distributed Inductance (L') For a coaxial cable, the inductance per unit length L' in henries per meter (H/m) is defined as. Calculate the impedanceThe correct way to consider impedance matching in transmission lines is to look at the load end of the interconnect and work backwards to the source. ε0 = permittivity of free space = 8. On Figure 5, the. The VSWR/return loss calculator from Pasternack will find VSWR, return Loss, mismatch loss, and the reflection coefficient given any one of the listed input types. Where L is the length of the dipoles. For the cost, ladder line has lower loss than coax. These connectors have screw type coupling mechanism which minimizes reflections and attenuation by ensuring uniform contact. Tuesday, October 31, 2023. When attaching a 200 Ω balanced antenna to a 50 Ω unbalanced (coaxial) cable, connect the high impedance (200 Ω) balanced antenna to the high impedance side of the transformer, and the low impedance (50 Ω) unbalanced end to the low impedance side of the transformer. As we know that the definition of the return loss of a system is the ratio of incident power to. It is important to determine the characteristic impedance of a twisted-pair cable because this impedance should match the impedance. In an RF system, when power is sent from the source to load, there are three main parameters to be considered: (1) incident power. 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. Input. Designing a Current-Mode-Controlled Buck Converter in LTspice by Robert Keim. c is the speed of light 299,792,458 m⋅s −1,. To calculate impedance, we first calculate the voltage between conductors and the current flowing in the inner conductor. So… If you need a 1/4 wave piece of coax for, say, 7. 5nF. Question 17. 295+j32. This ratio represented in dB is called as Return Loss. 2. d is the diameter of the inner conductor of the coax cable; units of D and d must be the same,. × 10 −12 F/m is the. 150 MHz = 41. How is the turn ratio calculated? The turn ratio of the RF transformer is calculated by using the following formula. Altium's built in impedance calculator shows the trace impedance at 34 ohms not 50 ohms. If it's safe to assume that both drivers have an output of the same amplitude, we can even calculate the loss introduced by the cable: 20×log(1. Figure 4 shows calculated results on a 5m long good quality single braid coaxial cable, 1 meter above ground, with perfect 360° contact at connector backshell. The velocity factor of a foam insulated cable depends on the production technology and varies from manufacturer to manufacturer. Brown part is the copper itself. 035 in), outer conductor diameter 3. ) using the high and low frequency approximations above for Rc and Lc. Step by Step Procedure The 125 ohm cable is connected at the end of a regular 50 ohm RG-213 cable. VSWR is defined as the ratio of the maximum to minimum voltage on a loss-less transmission line (expressed as 3. Simply put, the coax is losing 8. This is the only way to calculate the total impedance of a circuit in parallel that includes both resistance and reactance. 9. To use the calculator, select the type of RF cable type and enter the outer diameter. The nice part about coax is that it can be bent and flexible unlike most pcb transmission lines. 854187817620. Models have been created to approximate the characteristics of the coax cable transmission line. Impedance per unit length (Z) Ω. 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. 66 kW Black TPE Jacket (. 35dB. R2 is the resistance of the protective conductors. the built-in transfer impedance calculator, which extracts the impedance from the geometric characteristics of the shield. For this calculation the diameter and length units are in cm. 0, medical, smart city, and other applications that are impractical or impossible with other wired and wireless technologies, providing twice the bandwidth and three times the speed of Wi-Fi 6, deterministic network support, and more…. The RG-8A/U is a 50-ohm coaxial cable with an outside diameter of 0. A Folded dipole antenna is a half-wave dipole antenna with an additional parallel wire or rod connecting its two ends and folded to form a cylindrical closed shape. ε 0 = 8. Twisted pairs are used with balanced signals. 900c. LOGIN. Off-center coax. … 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. Feedpoint impedance and coaxial matching section. Where we basically use the effective area instead. Distributed Inductance (L') For a coaxial cable, the inductance per unit length L' in henries per meter (H/m) is defined as. A little more generally, a quarter-wave section of transmission line of impedance Z 0 converts between two impedances Z a and Z b: Z 0 / Z a = Z b / Z 0. Lower VSWR is always desirable for a system. 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. 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. A slot or gap with a conducting coating on a dielectric substrate makes up a slot line, a form of transmission line comparable to CPW. This configurator will generate a bill of materials for a Constellation power delivery system. For example, if you wish to input "25000000", just type "25M" instead. 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. This CalcTown calculator calculates the capacitance, inductance, impedance and various other parameters related to a dual dielectric coaxial cable. This is the only way to calculate the total impedance of a circuit in parallel that includes both resistance and reactance. 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. The coaxial cable (coax) is one of the most ubiquitous transmission line structures. × 10 −12 F/m is the. The most common values of coaxial cable impedance are 50 and 75 ohms. 1. 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. See Figure 2. Surge Impedance Calculation 35 100 0. 4. It has an inner 7-stranded bare copper. 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. Calculate ZO from the formula above. Insulation service (cable tray, conduit, direct burial, etc. Here is my measurement to a piece of RG6 cable. 9 mm (0. D is the outer diameter of the cable. Picking it interactively in the 3D view and. 4. R is resistance per metre, L is inductance per metre, C is parallel capacitance per metre and G is parallel. . For coaxial cables the characteristic impedance will be typically between 20 and 150 ohms. EEWeb offers a free online twisted pair impedance (transmission line) calculator. Technical Recap: Coax feed line chokes all have unbalanced input and either balanced (BALUN) or unbalanced (UNUN) output. The return loss of a system is defined as the ratio of incident power to reflected power and is measured in dB. Since we might as well find the impedance per length, we can study the expression: Rl = 1 σA R l = 1 σ A. ε 0 = 8. 3. 854187817620. - Example: 2nd mode in coaxial cable is a dipole TE 11-mode - This dipole mode changes polarity twice around cable circumference - Approximation: Use average circumference 11= =𝜋∙ + 2 - In coaxial line the TEM-mode is the dominant mode - The corresponding wavelength equals the cable circumference C, but at which radius? 11= vpoint along a transmission line with a general load impedance. 96. An air-spaced cable would shift signals at the speed of light c. This calculator can also be used for measuring coaxial cable and will then give Relative Dielectric Constant rather than Effective Dielectric Constant. 6/1. The Smith Chart achieves this by superimposing a grid on S11 that maps load impedance. d is the diameter of the inner conductor of the coax cable; units of D and d must be the same,. Distributed Inductance (L') For a coaxial cable, the inductance per unit length L' in henries per meter (H/m) is defined as. . 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. D (mm) Er d (mm) Impedance Notes: Optimal D/d ratio for breakdown voltage is 2. on the calculator devide 29. Gamma matching is the most commonly used matching device used for a planar dipole in the Yagi-Uda antenna. We recently corrected a problem with the cut-off frequency calculation for single dielectric, which was pointed out by Andrew (thanks!) It will calculate characteristic impedance of coax that contains up to five concentric dielectrics!You can find online coaxial cable impedance calculators that accept inputs of outer diameter dielectric width, inner conductor diameter width and either the dielectric constant or velocity of propagation (VoP, the speed at which RF propagates through the cable conductors) values to calculate the intrinsic impedance of the coax. Brown part is the copper itself. Choose from a variety of cables and get started now!. Show Me Cables' high quality RG6 quad shield coaxial cable consists of an 18 AWG solid bare copper. The length of a half-wavelength dipole can be calculated by the given formula: L =. In fact, striplines often make components such as band-pass filter's more accurately, with more symmetric roll-off and no lower cutoff frequency. The coaxial cable is so fundamental that Oliver Heaviside patented it in 1880, just a few years after Maxwell published his famous equations. But it is not applicable to large and non-symmetrical cable-connector system as. Note: The value of μr in this calculator has been taken as 1. On the shield is written COAXIAL CABLE 5C-2V 75 ohm. Coaxial Cable Impedance Calculator. Twisted-Pair Impedance Calculator; Embedded Microstrip Impedance Calculator; Microstrip Impedance Calculator;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. 125 MHz. 5 mm Coaxial Connector is designed to be relatively rugged. The coax cable has a capacitance as a result of the gap between inner conductor and outer shield of the cable. If you would use different values, the signal would reflect and distort itself. 95 metersA microstrip width calculator can calculate the width of a microstrip. This causes an impedance mismatch at each staple location resulting in micro-reflections. 5 in. The impedance can be calculated by the following formula. Now, to calculate the necessary line length: assuming that our cable has a velocity factor of 0. i cant find the datasheet though it has part number 473-872-03 Rev A1 Mfr 64023. 5:1 . For this example, assume perfect conductors and a lossless dielectric with relative permittivity ε r = 2. In electrical engineering, the reflection coefficient is a parameter that defines how much of the electromagnetic wave is reflected due to the impedance discontinuity in a transmission path. The area just becomes the effective area, so for the inner shell, 2πaδ 2 π. The concept of Shield Transfer Impedance (Zt), introduced by S. Bend Radius is the minimum radius that a Radio Frequency (RF) coaxial cable can be bent to without damage. Both components receive a current simultaneously, generating a magnetic field. This model computes the electric and magnetic field distribution inside of the coaxial cable. e. μr μ r = relative permeability. But for a practical transmission system with load, there will be a small impedance mismatch that will lead to a small amount of incident power reflected back to the source. In particular, as radio frequency (RF) signals pass through coaxial cable, connectors, attenuators (pads), equalizers, and passive components such as splitters and directional couplers, those RF signals. A Coaxial cable is a type of cable that is used to make transfer RF/Microwave signals. Suitable for higher power (~1800 watts) at HF. 1. Choose from 50 Ohm, 75 Ohm, 93. Figure 2 - Fast pulses measured at the end of the coaxial cable using an oscilloscope without impedance matching. It's primarily intended for radio and data communications. Over time properties of standard coaxial type cables have been standardized. Suitable for higher power (~1800 watts) at HF. As the name suggests, the length of this transmission line if fixed at a quarter of the wavelength (λ/4). in both cases, the speed and the Characteristic Impedance depend upon logarithms of the ratio of two distances in the cross. I used 100m for l. 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. 0815. 854187817620. The coaxial cable, along with the balanced two-wire, is the most common type of transmission line used in RF communications. Broadcast and Satellite Cable. 13-1. Another way is to use ladder line. Coaxial cables are extremely useful transmission lines as the coaxial nature of the transmission line provides relatively efficient transmission from DC to a cut-off frequency, which is a function of the geometries of the coaxial components of the cable. What we call attenuation or loss is a decrease in the power of a signal or signals, usually measured in decibels. Zc = characteristic impedance of cable-above-ground transmission line. Customers can choose to either buy cable in bulk or use our large selection of coax types to construct custom cable assemblies. A coaxial cable of a specific impedance is determined by the ratio of the dimensions, not the absolute values. 5 x center F chosen. 36Ω), the impedance is: Transformed through 25 feet of RG-8 coaxial cable to 111. Then use the LCR Meter and measure the inductance at the open end of the cable. This formula is from the following reference. Good enough, because the calculation for 15 m of typical coax with 6. Some systems use 75 Ω; this latter value is more appropriate for high-speed digital signals. Looking at the datapoints and moving back from the antenna (75. 66) / 10. 124 in), type of insulation is polyethylene with the relative permittivity of 2. 2. The distance in time between adjacent pulses is 35. Ze is the external earth loop impedance. A series of RF calculators for radio frequency engineers. . . c is the speed of light 299,792,458 m⋅s −1,. Here are the coax topics covered on this page and other related pages: Coax overview. A-INFO carries hundreds of RF cables all in-stock and available for same-day shipping worldwide. I used 100m for l. Here is my measurement to a piece of RG6 cable. The velocity of propagation along the wire is 2x108 m/s. This calculator is able to calculate the impedance, delay, inductance, and capacitance of a coaxial cable. Coaxial Impedance Calculator. U. c is the speed of light 299,792,458 m⋅s −1,. The Pi attenuator (Pi pad) is a specific type of RF attenuator circuit which resembles the shape of the Greek letter for Pi. Coaxial cables are commonly used for transmitting electrical signals, including RF (radio frequency) signals. If you want to put this thing outdoors, do not use brass, as it gets brittle. coaxial cable. Coax Impedance Calculator | Sivers IMA. 7mm. Distributed Inductance (L') For a coaxial cable, the inductance per unit length L' in henries per meter (H/m) is defined as. This may not seem much of a loss but look at the Power Compensator again and you will see that 100w from your transmitter would have to be increased to 108. 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. This works from DC to 1. If you use the formulas in the table below you will calculate a VSWR of 1. Coaxial cable is typically rated to operate at 50 or 75 ohms so the scale should be at or greater than these ratings. 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. Use RG 58 cable (or any 50 ohm cable) You will ear the. Characteristic Impedance (Zo) 50 (±2) ohms. coax cross section. The distance in time between adjacent pulses is 35. This is a required field. Micro-coaxial cables. UsefulFormulas. This online reflection coefficient to VSWR calculator calculates the VSWR by entering the reflection efficient Γ (= value between 0 & 1). 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. 04 feet = (246 x . My thoughts: The source sees from DC to approximately 300 kHz 117 Ohm Real Component (as 2x50 Ohm + 10*1. 25 inches. f if the frequency of the RF signals. This online reflection coefficient to return loss calculator calculates the return loss (dB) by entering the reflection efficient Γ (= value. 1: Determining the inductance of coaxial line. All Answers (17) The attached formula is used to calculate the characteristic impedance of coaxial probe, where: (d) is the inner diameter of coaxial probe. It is horrible! At the compromise value of 50 ohms, the power has improved a little. I leave it to other sources to provide the complex equations needed to precisely model coaxial cables. a suitable coaxial cable and, instead, insert a suitable thinner inner con-ductor leading to a higher characteristic impedance. Email. 5). Polar or rectangular grids only allow direct reading of S11. 124 in), type of insulation is polyethylene with the relative permittivity of 2. 1,857. V is calculated by integrating the electric field along a path from the. VSWR (voltage standing wave ratio, sometimes pronounced "viswar"), is the ratio of the maximum standing wave amplitude at one node to the minimum.