It supports both balanced and unbalanced lines. Class creation for controlled impedance routing using Altium Designer. 0. Example. Careful readers will note that Eq. Archimedes constant (π) Impedance Calculator Results (detailed calculations and formula below) The Impedance of the circuit is Ω. Γn is the reflection coefficient. A Target Impedance of 50. The Nano has to drive a 50 ohm load when the terminator is present. To calculate, enter the inductance, the resistance, and the frequency, select the units of measurements and the result for RL impedance will be shown in ohms and for the phase difference in degrees. 5:1. Inductive reactance XL= Ω. May 5, 2021. The Speaker Ohm Calculator is a useful tool for audio enthusiasts and professionals who are setting up sound systems. Input these values into the following formula: P = 10^ [ (loudness-sensitivity)/10] Find an amplifier rated for this power output at your headphone's impedance. This is true for many materials, over a wide range of voltages and currents, and the resistance and conductance of electronic components made from these materials remain constant. The tool provides two networks that will have the desired impedence at that frequency, but their. The normalized impedance z L = Z L /50 ohms =. 73Ω. Since the impedance is a real number, the voltage is in-phase with the current. The voltage across a 100-ohm resistor depends on the current flowing through it. C is the capacitance in farads (F),. Draw a circle through this point around the center. This will give the highest bandwidth measurement and lowest noise level. Not perfect, but it improves the return loss from -6. In the forthcoming simulation, I want to match a 50 Ohm driver to a 70 Ohm antenna, so the impedance of my matching network plus the load needs to be 50 Ohms. 1. So for example 160-20 is 140, divide by 2 and add to the 50 from your through. The quick answer is that 50 ohms is a great compromise between power handling and low loss, for air-dielectric coax. 2361E+04. Board. Note: Units for width and height must be consistent Calculation Width: Result: 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 the copper trace (W), and dielectric height (H). D D = coaxial cable outer diameter. Does it even have an impedance? Yes, it does, it is called the "wave impedance". Here is a short list of potentially useful calculators for your endeavors: Ohm's law calculator; Wire resistance calculator; PCB trace current calculator; and; PCB trace resistance calculator. Why is 50 ohm used? The 50-ohm impedance is commonly used in RF (radio frequency) systems due to its compatibility with coaxial cables and minimizing signal reflections. Gilmour, Jr. It is important to determine the characteristic impedance of a twisted-pair cable because this impedance should match the. Stack Exchange network consists of 183 Q&A communities including Stack Overflow,. However, this applies only for the. Transform a Complex Impedance Through a Transmission Line Start with an impedance Z i = 27 + 20j ohms The normalized impedance for a 50 ohm line is z i = 0. For 25 ohms, we calculate 31 mils line width and 7. The tee (T) attenuator (pad) formula in the calculation for resistor values is measured in Ohms. The microstrip is a very simple yet useful way to create a transmission line with a PCB. 8 substrates of various thicknesses. To calculate the required transmission line lengths in meters for the placement of the stubs, analyze the microstrip to obtain a phase velocity value. These equations are relatively simple compared to other transmission line. Modern ICs that are intended to be used with transmission lines normally implement on-die termination at the driver end, and possibly at the receiver end. For those students who calculate a time figure that is half as much as the one given in the answer, encourage them to think of why their (incorrect) answer might have been off by 50%. If the source is monitored with a high impedance-measuring instrument -V an oscilloscope with a 1 M-ohm input, for example, it would produce very nearly 2 Vpp – even though the output indicator on the instrument indicates 1 Vpp. 75 Ohm power dividers / splitters come in 2 Way, 4 Way or 8 Way. Values of 50 Ω 50 Ω and 75 Ω 75 Ω also offer some convenience when connecting RF devices to antennas. 2 are defined as. The image below shows a schematic of my impedance matching network. You can easily match your antenna to a 50 Ohm line using a quarter-wavelength transmission line (QWT), and the dimensions depends on the input impedance of your designed patch antenna. Divide the 1/4 wavelength by the velocity factor to get the electrical 1/4 wavelength. Output field. 2, the following formula can be used: Zo = 138 * log10 (D/d) / sqrt (εr) where Zo is the characteristic impedance, D is the diameter of the outer. f c = 1 / (2π × 3. Well, first of all: that was the normal relation for impedance transformers: Z_T=sqrt (Z_L*Z_A) with T denoting the characteristic impedance of the transformer line, L the line impedance which you want to obtain in the end (e. 035mm and Er = 4. The cct. The air lines currently used as impedance standards are discussed in section 4, below. It is chosen for its balance between signal loss and power handling capability in RF applications. eu. I used some online calculator to calculate parameters of trace so it has 50 Ohm impedance. The advantage of using coax for a 1:1 choke-balun is the constant Z0 of 50 ohms. You want to set R T to equal the differential characteristic impedance of 100 Ohms, so there is no reflection. 25 ohm load to 50 ohm coax, also know as a 1:2 balun). Pasternack's RF Power Dividers (also known as RF power tappers or coaxial splitters) are available in both 50 Ohm or 75 Ohm impedance designs. 5mm, T=0. There are some advantages to using a microstrip transmission line over other alternatives. 50 ohms is in the middle, short circuit on the left, open circuit is on the right. Required Data Entry. You can input the capacitance in farads, microfarads, nanofarads, or picofarads. If you look through search engine results, you’ll find plenty of links to calculators that can help you properly match the antenna tuner load impedance with. That said, the impedance mismatch between 30 and 50 ohms isn't that much. Finally, calculate the Voltage From Impedance using the formula above: E = Z * I. 5. Therefore, if you want to deliver the most RF power from your 50-ohm source to your antenna - voila, only a 50 ohm. I used an HP 141T/8553B/8552B spectrum analyzer, 8443A tracking generator, and. 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),. This calculator can calculate the impedance and propagation delay of the embedded microstrip. R is the resistance in ohms (Ω),. This requires you to route the traces farther apart in order to hit a standard 50 Ohm impedance goal. Both the unit and the rule are named after Georg Ohm - the physicist and inventor of Ohm's law. Ohm’s Law Calculator. 52mm. So, the driver drives into 50 Ohms (100 // 100). Enter values for W and L for a microstrip line to determine its Zo and Electrical Length. 4 49. Twisted pairs are used with balanced signals. This is true for many materials, over a wide range of voltages and currents, and the resistance and conductance of electronic components made from these materials remain constant. The second major factor which affects impedance is the distance from trace to the nearest plane. 5 or 6. Headphones with impedance of 32 ohms would be louder than 48-ohm headphones with the same signal voltage because there would be more power on account of the lower load resistance – provided that the amplifier has low source resistance. An Inductor Impedance Calculator is a tool used in electrical engineering and electronics to calculate the impedance of an inductor in an alternating current (AC) circuit. 8 Mils and the FR-4 dielectric of 3. Engineers can use the parameter for understanding how the antenna is matched (good or poor). φ = –90° if 1/2πfC > 2πfL and R = 0. Both the S-parameter and input impedance are complex numbers (R + jX), where R represents the real component, and the X represents the imaginary component. VSWR (voltage standing wave ratio, sometimes pronounced "viswar"), is the ratio of the maximum standing wave amplitude at one node to the minimum amplitude at another node in a system. In this case, the total effective resistance is 2 Ω. Inductance – the impedance calculator uses the Impedance value to calculate the inductance per unit length. It is the ratio. You’ve probably also seen some calculators. The impedance of this line in ohms can be estimated with Eq. For dipole antennas with an impedance greater than 50 ohms you will need a step up impedance transformer (e. In this case, we can use: Pspeaker = Ptotal (total power) x Speaker1/ (Speaker1 + Speaker2) This gives us: P1 (power to speaker one) = 25W*8/ (16) = 25W*0. These values suggest the range of impedance, where you will not compromise both power and signal loss. Note that the SWR changes only slowly with Xa and XL so great accuracy in their selection is not required. 50 Ohm Attenuator Calculator. Understanding Amplifier Power. Jun 16, 2011. Make sure it is within your headphone's input limits to avoid damage. 60. There is also a selection of 50 Ohm RF connectors available. Inductance – the impedance calculator uses the Impedance value to calculate the inductance per unit length. *Strictly, a loss quantity when expressed in dB should be positive. Lcoax ≈ μ0μrL 2π ln( D d) L c o a x ≈ μ 0 μ r L 2 π l n ( D d) Where: Lcoax L c o a x = inductance of the coaxial cable in henries (H) μ0 μ 0 = permeability of free space = 4π×10 −7. These are pure estimates to. Resistance is expressed in ohms. 8-j0. This can be built into a FLEXI-BOX and a transmission line (50 Ohm track) PCB is available which easily adapts for this circuit with one simple trimming. It helps you determine the total impedance (in ohms) when connecting speakers in series or parallel. There are many demands placed on PCB stackup design. 50 Ω first arose as a nominal impedance during World War II work on radar and is a compromise between two requirements. 4 Ohm , Radiation Resistance Equation. Rough Line With Dispersion. Enter values for W and L for a microstrip line to determine its Zo and Electrical Length. Index: Aerial Calculations : Balun Theory. Twisted pairs are used with balanced signals. The most important are: PCB Material; The PCB material are standardized with different norms. You can use this formula for individual resistors in a parallel circuit. e. 405" 75 ohm coax for the feedline, RG-11U or. Impedance in your traces becomes a critical parameter to consider during stackup design for high-speed PCBs, but the. A perfect match corresponds to Γ = 0, and a complete discontinuity (in which all the energy is. The decision to use low impedance, 4 ohm or 8 ohm loudspeakers, or a high impedance (often called “Constant Voltage” or “70Volt”) system is not a straight forward matter in system designs that use large format loudspeakers or are distributed over a substantial distance. Figure 2. X c = 1 / 2πfC. #2. With t = 35 um (typical for copper with plating on a pcb), Z odd drops to 44 ohms, according to LineCalc. Significantly, the on-line calculators that invoke Q factor as a parameter don't appear to justify what it means or how to use it. 675 ohms. I wanted to use Altium to calculate the width of the trace automatically, so that it had a 50 Ohm impedance. For Commercial. 4mil. Let’s say you have a transmission line with a Characteristic Impedance (Z0) of 100 Ohms and a Common Mode Impedance (Zc) of 20 Ohms. It is horrible! At the compromise value of 50 ohms, the power has improved a little. (Default Values Below Usually Work Well For Line to Mic Attenuation) Input Impedance (Source impedance) (600 ohms for modern rigs)Impedance matching on antenna is done by measuring reflections in a splitter or the maximum Return Loss by trimming dipoles for example. Let the PCB manufacturer know of your intention to request the manufacture of a 6-layer board. When describing impedance, there are several terms that you should aware of. - For the obtained Zo in your Smith Chart calculate. Enter the source characteristic impedance and the load impedance then press "Calculate" below. Coaxial Cable Impedance Calculator. Using it as a transformer rather than to make sparks. Products. Following formula can be derived for the characteristic impedance of a parallel wire transmission line: 1. 6 mil "measured copper top to bottom" er of FR4 = 4. Consider a DC photovoltaic Solar cell. a) Reduces the diameter of the pin through the connector, while keeping the diameter of the mating part. 0 value of the line to this point on the chart—50 Ω for a 50-Ω line, for example. Here is how we calculate this. 2 in. Here, my simulation source is a simple AC source (labelled V2, found in the Simulation. R is the resistance in ohms (Ω),. Here, we use a 50 Ohm characteristic impedance cable, such as an RG58 or RG174 cable. For example, 1oz, 10 mil traces, with 6 mil to the ground plane, and Er=4. If the load is reactive, this calculation must be done using complex numbers. Using the Microwaves101 microstrip calculator, we see that 50 ohms on 10 mil alumina corresponds to 9. Find coefficient of reflection (mag, &. 3 kΩ resistor and a 47 nF capacitor (which are standard resistor and capacitor values). View All Tools. The most common values of coaxial cable impedance are 50 and 75 ohms. Consider a DC photovoltaic Solar cell. 24 ohms. The quality of an impedance match can be expressed mathematically by the reflection coefficient (Γ). Sierra circuits have an online one for coplanar. Yes, we did that without a calculator. Tee (T) attenuator calculator from Pasternack allows you to determine the resistor values (R1 & R2) for a the RF component. Classes for 50 and 100-ohm traces. One of the most common is FR4. The image below shows an example Smith chart used to plot the impedance Z = 1. You can then calculate the length in degrees for nearby frequencies with reasonable accuracy. The impedance of the line is mainly depending on your PCB characteristics. The calculator produces more accurate results than the IPC formulas for impedance because it. 1- Assume the load is 100 + j50 connected to a 50 ohm line. The fact that all our gear is designed and. 0). 50 Ohm Attenuator Calculator. Note that there is no single impedance because the driver's output impedance value will depend on the drive strength and the. d d = coaxial cable inner diameter. 2-side PCB, one side with signals, the other with GND. This. It is important to determine the characteristic impedance of a twisted-pair cable because this impedance should match the impedance. The PCB material will be FR-4 with 1. 1-2 GHz is kind of a messy middle ground where you might get. There are many factors that go into calculating the width of an impedance controlled trace. Also, the real part of the impedance will not saturate exactly to 50 Ohms; it will fluctuate around this value. Keep in mind that the reactance of the ideal inductor has the same magnitude as its impedance. On the right is a calculator for determining the wire length and feed impedance for a Folded Dipole. 3 ohms and reactance of 5000 ohms. These calculators should be avoided for high-speed design and RF interconnects. Below 1 GHz, this discontinuity is usually too small to worry about unless you're doing something like precision radar work. Zo (section impedance) = Z1 (cable 1 impedance. For the sake of simplicity, input return loss. So if you use the connector with a high impedance load it will look like a high impedance, not 50 ohms. Calculate the power needed to drive your headphone based on sensitivity (db/mw or db/V), impedance (ohms) and loudness (dbSPL)L Match Impedance Calculator. Both input and output impedance is set to a default value of 50 Ω. The circuit can easily be adjusted for 75 Ω Ω lines simply. These quantities - source impedance, line impedance and load impedance, respectively - must equal one another (impedance matching]) to ensure the efficient transmission of power. This characteristic impedance is close to the desired 50-Ohm impedance, so the example can proceed with the design using these microstrip lines. f is the frequency in hertz (Hz),. This calculator is designed to calculate the characteristic impedance of an embedded microstrip - a flat conductor suspended over a ground plane with a dielectric between it and another dielectric material. Draw a circle through this point around the center. impedance ratios other than 1:1 because accommodation must be made for the impedance of test instrumentation, which is generally a constant 50 or 75 ohms. The purpose is to stabilize variations in line impedance using L1 which raises the impedance to above 50 Ohms above 150kHz for conducted emissions between 150kHz and 30MHz. Above 5 GHz, you'd generally want to carefully design your via to maintain impedance matching as well as possible. One of the most common is FR4. 2,148. 5mm, T=0. This L1 is equivalent to a short power line of 25m from a low Z distribution transformer to the DUT. Bookmark or "Favorite" this microstrip line impedance calculator page by pressing CTRL + D. This antenna operates at 1. ω = 2πf is the angular frequency in rad/s, . The scope displays only 1/2 the waveform amplitude that the signal generator says is. Figure 1. It depends on the speaker’s efficiency and design, but a rough estimate is that a 4-ohm speaker can handle around 50-100 watts RMS power. By combining these two previous equations, we can compute the power by just knowing the resistance and the voltage or any two of the three main electrical variables (V, I, R). There are at least two ways to calculate it. RF calculations and RF conversions include metric. The generalised formula for the input impedance of any circuit is ZIN = VIN/IIN. The lower the SWR value, the better antenna matched (usually 50 Ohm, 75 Ohm for TV networks). If this were a load on the line, we recognize from transmission-lineThe key design criteria are the magnitudes and relative sizes of the driving generator output impedance and load impedance. All the calculations were performed as described in the standard IPC-2141A Design Guide for High-Speed Controlled Impedance Circuit Boards. You would like to measure the input impedance of your circuit with a 50 ohm network analyze. You can then calculate the length in degrees for nearby frequencies with reasonable accuracy. These equations are relatively simple compared to other transmission line. At your frequencies (10MHz) you can pretty. 𝑍c = 𝑍0𝜋 𝜖r−−√ acosh(𝐷𝑑) (1) (1) Z c = Z 0 π ϵ r acosh ( D d) The characteristic impedance of free space is exactly: 𝑍0 = 𝜇0𝜖0−−−√ = 𝜇0 ⋅ 𝑐0 ≈ 376. To increase voltage the output impedance just has to be higher than the input impedance. Post subject: 50 Ohm TO 75 Ohm Posted: Wed Feb 21, 2007 12:53 pm . While it's not explicitly stated, the voltage in this case represents the root-mean-square value or VRMS. This assumes ~0 trace thickness. Alternatively, Generate R1 and R2 for a wanted attenuation. , the output has been matched for 50 ohms, since half the power. The rules shown below are a rough approximation, and you should always check the approximation using an impedance calculator or field solver. Vrms is the Voltage in volts. 3. In practice, we will never have a perfect, ideal system. With the Multi-CB impedance calculator, you can calculate the approximate impedance dimensioning of your PCB / high frequency circuit board. where X c is the capacitive reactance. This tool will also compute the resistance of the stripline, the voltage drop on it, and the resulting power dissipation. #5. ) always provide better loss than a 75 Ohm cable. φ = 0° if 1/2πfC = 2πfL. The cct. The impedance of coaxial cable will be about 52 ohms, depending on the exact cable. So the phrase "minimum loss pad" is a cruel joke indeed!Coaxial Cable Impedance (Ohms) Impedance is the amount of resistance waves moving through the coaxial cable encounters. 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. 5GHz and needs a 50 ohm impedance line. The phase is mostly + 90 ∘ or − 90 ∘, indicating that Zin is mostly reactive. For a pure capacitor of capacitance C Farads, the impedance ZC = 1/jωC Ohms. Display the answer in ohms. Angular Frequency ω= rad/s. an ideal microstrip you'll determine from a calculator. In this ideal scenario, no power is lost, and the VSWR value is 1 : 1 , which signifies 100% transmission of the input power from the source. for matching 60 ohms to 50 (Z1/Z2=1. Set the scope input impedance to 50 Ohms. 33 of the transmitted voltage, and this leads to a 2:1 VSWR, in a 50 ohm system. 3mm) and calculate the anti-pad (AP) size that is required to present a nominal 50 Ohm impedance at this point. The ratio of signal reflected back from the load to the forward signal absorbed by the load in dB is called return loss. This tool calculates the matching network necessary to terminate a line of the specified characteristic impedence (Z o) in a specific complex load impedence (R L + jX L) at a specified frequency. 75 mm=30 mil). To adjust for this, would I, using the online calculator Andy used, set the output impedance for the matching network to whatever the antenna impedance actually ends up being instead of 50 ohms? And. Selecting the Layer Material. A few turns for each side around a ferrite is probably good enough. Most RF test equipment has 50 ohm output impedance and 50 ohm input impedance. This calculator will help you determine the correct values for the inductor and capacitor in a Pi match impedance matching. It is a theoretical thing. Here’s how to navigate it: Input Fields: Start by entering your headphone’s specifications, including impedance and sensitivity. Doubt about 50 ohm impedance calculation. 4. Write down your headphone's impedance (Ω) and sensitivity (dB @ 1 mW). ω 0 = resonance angular. 73Ω (2) (2) Z 0 = μ 0 ϵ 0 = μ 0 ⋅. For more demanding applications, special high-frequency PCB materials (for example: Rogers RO4000 [2]). The 75 ohm version of a 50 ohm connector (at least for the SMA, N and BNC types that I've studied) raises the impedance in two ways, while keeping the mechanical interface identical. Simulate and then insert a list ofThe purpose is to stabilize variations in line impedance using L1 which raises the impedance to above 50 Ohms above 150kHz for conducted emissions between 150kHz and 30MHz. 1) If using 50-ohm series resistor on each signal line, do the traces still need to be 50-ohm impedance controlled on PCB? 2) And if so does the impedance need to be controlled. Plots of (a) SWR and (b) XL for hairpin matching to a 50 ohm line. 03556mm. The differential pair impedance calculators you'll find online provide a good first estimate of the impedance you can expect for your particular geometry. 5 ohms (to match with a quarter wavelength of 75 ohm coax) or 200 ohms (to match with a 4 : 1 balun, or a quarter wavelength of 100 ohm balanced line: a pair of 50 ohm coax cables side-by-side, or standard American 2-conductor electrical cord is about 105 ohms). EEWeb offers a free online twisted pair impedance (transmission line) calculator. You only need to know the resistance, the inductance, and the capacitance values connected in series or parallel. At frequencies where 50 versus 75 Ohm impedance matters, it can be quite small. Suppose our unmatched load impedance is Z = 60 - i35 Ohms; if the system impedance is 50 Ohms, then we divide the load and system impedances, giving a normalized impedance of Z = 1. To calculate impedance, calculate the resistance and reactance of the circuit, then label resistance as R and reactance as X. The outer/inner surface ratio across the gap increases for 75 Ohm Cable for TV. High-speed designs carry a requirement for controlled impedance, crosstalk control, and the need for interplane capacitance. Both input and output impedance is set to a default value of 50 Ω. Therefore,Here, we know the value of Z0 is the source impedance at the network input (50 Ohms), and we need to calculate Znetwork, which is the input impedance of the network (in other words, the network + load impedance). For the sake of simplicity, input return loss (S 11. When Would You Use a 50-Ohm Oscilloscope. Saturn PCB - Toolkit for Impedance Calculation. For those who use 0. INPUT DATA : Source Impedance: Ohms: Load Impedance. Our RF and microwave calculators and converters will provide the figures you need for your radio frequency engineering needs. 50 Ohms. 33 of the transmitted voltage, and this leads to a 2:1 VSWR, in a 50 ohm system. The surface finish is neglected. 50 ohm output is pretty much standard for function generators, as it is a match for the 50 ohm coaxial cables that are often used to interconnect equipment. According to this app note from Analog Devices, you can create a 50 Ω microstrip as follows: 1-ounce copper, 20-mil-wide trace, 10-mil separation between trace and ground plane. This L1 is equivalent to a short power line of 25m from a low Z distribution transformer to the DUT. L is the inductance in henries (H),. Attenuation field. Z O is usually a real impedance. There. High-quality circuit boards as prototype and series at reasonable prices. 50 Ω and 75 Ω. The L match circuit gets its name because the circuit topology can look like the letter “L”. In either case, the resulting VSWR is 1. An Inductor Impedance Calculator is a tool used in electrical engineering and electronics to calculate the impedance of an inductor in an alternating current (AC) circuit. 1. In fact, striplines often make components such as band-pass filter's more accurately, with more symmetric roll-off and no lower cutoff frequency. Video signals usually are required to be routed at 75 Ohm impedance if they go off-board. When I calculate the necessary values for an LC impedance matching circuit, I end up with extremely high values necessary for capacitance (e. So lets assume you want a 50 ohm impedance trace and you are using 1oz copper and have a standard 0. 2 - i0. A common dipole, driven from the center and 1/2 λ above ground, will exhibit approximately 72 Ω of impedance. 50 ohms is most often used for radio transmitting and receiving applications. Most RF circuits are designed for 50 ohm impedance. Fortunately, a 1/4 wave each of 50 ohm and a 75 ohm paralleled will provide a 30 ohm cable. The reflection coefficients at each boundary in Figure 7. Figure 6. I was told that copper at. 57 pF can be used to match the two impedances. Capacitor, Reactor, Transformer, Cable, etc. Related: resistor calculator Ohm's Law. When viewed as a simple electronic circuit, the impedance of the audio source may be written as output (or source) impedance, while the impedance of the headphones may be considered load impedance. I use FR-4, so H=1. Capacitance – the impedance calculator uses the Impedance value to calculate the capacitance per unit length. V - voltage. Divide the sum by the total number of speakers to find their average rating. Calculate the power needed to drive your headphone based on sensitivity (db/mw or db/V), impedance (ohms) and loudness (dbSPL) L Match Impedance Calculator. I am trying to create a PCB trace line from a GPS receiver to a GPS patch antenna. Enter the inductance and frequency values, select the units and click or tap the Calculate button. ω 0 is the resonant angular frequency in radian per second. 25 x 50 ohms). As the drawing shows, you can use 50 Ω or 75 Ω coax, without any real issues. 9. g. Admittance (Y) is the reciprocal of impedance (Z) and is often used in alternating current (AC) circuit analysis. different cables. Select "Unequal impedances" in the "Circuit type" box. The coaxial cable is a 50-ohm RG-174. Figure 3.