A Terminated Folded Dipole (T2FD) is a wideband antenna designed for multiple frequency bands. It exhibits reduced sensitivity to nearby objects and maintains balanced impedance (e.g., 300 ohms). With a design length approximately 0.95 times that of a standard half-wave dipole, it offers good impedance matching to various feedlines. This omnidirectional antenna typically requires a balun for optimal performance.
Terminated Folded Dipole Calculator
| Parameter | Description |
|---|---|
| Antenna Type | Terminated Folded Dipole (T2FD) |
| Design Purpose | Wideband antenna with reduced sensitivity to nearby objects |
| Operating Frequency Range | Typically covers multiple frequency bands |
| Impedance at Feed Point | Balanced (e.g., 300 ohms) |
| Termination Resistance | Commonly 300 ohms, but can vary based on design |
| Length of the Antenna | Approximately 0.95 times the length of a standard half-wave dipole for the same frequency, which can vary depending on the design and application |
| Balun Requirement | Often requires a balun (balanced to unbalanced transformer) to match the balanced antenna to the unbalanced feedline and reduce common mode currents |
| Directionality | Generally omnidirectional |
| Gain | Similar to a standard half-wave dipole, around 2.15 dBi |
| Bandwidth | Wider bandwidth compared to a standard dipole |
| Advantages | – Wider bandwidth than a standard dipole<br> – Reduced sensitivity to nearby objects<br> – Good impedance matching to various feedlines |
| Disadvantages | – Larger physical size compared to some other antennas<br> – Slightly reduced gain compared to other designs |
| Typical Use Cases | – Amateur radio (ham radio) communication<br> – Shortwave broadcasting<br> – General-purpose wideband receiving antenna |
| Installation Height | Typically elevated above the ground, but height can vary based on application and frequency |
| Tuning and Adjustments | May require adjustments in some cases to optimize performance |
| Construction Materials | Typically made from copper or aluminum wire |
FAQs
How do you calculate a folded dipole? To calculate the length of a folded dipole antenna, you can use the following formula: Length (L) = 468 / Frequency (in MHz)
What is the terminating resistor in a folded dipole? A terminating resistor in a folded dipole is typically used to match the impedance of the antenna to the transmission line and reduce reflections. A common value for the terminating resistor is 300 ohms.
How long is a T2FD antenna? A T2FD (Tilted Terminated Folded Dipole) antenna is typically around 0.95 times the length of a standard half-wave dipole antenna for the same frequency. So, you can use the same formula as for a regular dipole, but multiply the result by 0.95 for an estimation.
What is the size of a folded dipole antenna? The size of a folded dipole antenna is approximately half the length of a standard dipole antenna for the same frequency. So, you can use the formula mentioned earlier and divide the result by 2.
Does a folded dipole need a balun? Yes, a folded dipole antenna often requires a balun (balanced to unbalanced transformer) to match the balanced antenna to the unbalanced coaxial feedline and prevent common mode currents.
How do you calculate terminating resistance? The terminating resistance for a folded dipole is typically chosen to match the characteristic impedance of the feedline (e.g., 300 ohms) and can be calculated using the formula R = Z^2 / 300, where Z is the characteristic impedance of the feedline.
Why can you use a 120-ohm termination resistor? You can use a 120-ohm termination resistor when it matches the characteristic impedance of your feedline. However, 120 ohms is not a common value for feedline impedance, so it’s less likely to be used in practice.
How many ohms is a terminating resistor? The value of a terminating resistor can vary, but common values are 300 ohms or 75 ohms to match typical feedline impedances.
How far will a 16 dBi antenna reach? The range of an antenna depends on many factors, including power output, frequency, and environmental conditions. However, as a rough estimation, a 16 dBi antenna could reach several kilometers to tens of kilometers in line-of-sight conditions.
How long should a 2m antenna be? A 2m antenna, designed for the 2-meter amateur radio band (around 144-148 MHz), should ideally be approximately 1 meter (100 cm) in length for a half-wave dipole. However, practical antennas may be slightly shorter due to factors like construction and tuning.
What is the rule for antenna length? The rule for antenna length is that it is typically a fraction or multiple of the wavelength of the desired operating frequency. A half-wave dipole antenna is often used, which is approximately 0.5 times the wavelength.
Is a folded dipole better than a dipole? A folded dipole can offer some advantages over a standard dipole, such as a wider bandwidth and reduced sensitivity to nearby objects. However, whether it is “better” depends on specific requirements and use cases.
Is a folded dipole antenna directional? A folded dipole antenna, like a standard dipole, is generally considered an omnidirectional antenna, meaning it radiates and receives signals equally in all directions.
What is the gain of a folded dipole antenna? The gain of a folded dipole antenna depends on its design and dimensions. It can vary, but it is typically close to that of a standard half-wave dipole, which has a gain of approximately 2.15 dBi.
Should a dipole antenna be grounded? Dipole antennas are often not grounded themselves, but they may be connected to a grounding system for safety and to reduce the risk of static buildup or lightning damage.
Does a dipole need a 1-to-1 balun? A dipole antenna doesn’t always require a 1-to-1 balun, but using one can help match the antenna’s balanced feed point to the unbalanced coaxial feedline, reducing common mode currents and improving performance.
What does 2.5 fold mean? “2.5 fold” means an increase or expansion of 2.5 times the original size or quantity. It is equivalent to 250%.
What does 1.8 fold mean? “1.8 fold” means an increase or expansion of 1.8 times the original size or quantity. It is equivalent to 180%.
What does 1.5 fold mean? “1.5 fold” means an increase or expansion of 1.5 times the original size or quantity. It is equivalent to 150%.
What is a 50-ohm termination? A 50-ohm termination refers to a resistive load or resistor with a value of 50 ohms. This value is commonly used to match the characteristic impedance of coaxial cables and RF systems.
Why is a termination resistor needed? A termination resistor is needed to prevent signal reflections and ensure impedance matching in RF and transmission line systems, reducing the risk of standing waves and signal loss.
What is a termination load? A termination load is a resistive component connected at the end of a transmission line to match its characteristic impedance, minimize signal reflections, and ensure efficient power transfer.
How do you choose a series termination resistor? The choice of a series termination resistor depends on the characteristic impedance of the transmission line and the desired impedance matching. You typically select a resistor with a value that matches the line’s impedance.
Why do we use 250 ohms? 250 ohms is not a standard impedance value for RF systems, but it could be used in specific custom applications. The choice of resistor value depends on the characteristic impedance of the transmission line.
What is the total resistance on a CAN line with both 120-ohm terminator resistors installed? If you have two 120-ohm terminator resistors in parallel, the total resistance would be 60 ohms. In the context of a Controller Area Network (CAN) bus, a total resistance of 60 ohms is not the standard configuration, which is usually 120 ohms.
What does a 10,000-ohm resistor look like? A 10,000-ohm resistor, also known as a 10k-ohm resistor, typically has color bands such as brown, black, orange, and sometimes gold or silver. The physical size and shape can vary, but it’s often a small cylindrical component with wire leads.
What does a 20,000-ohm resistor look like? A 20,000-ohm resistor, also known as a 20k-ohm resistor, has color bands that might include red, black, orange, and sometimes gold or silver. Like other resistors, its physical appearance can vary, but it’s typically a small cylindrical component with wire leads.
How many ohms is a 1M-ohm resistor? A 1M-ohm resistor is a 1,000,000-ohm resistor. It is commonly represented with color bands such as brown, black, green, and sometimes gold or silver.
Which is better, 3 dBi or 5 dBi? A 5 dBi antenna has higher gain than a 3 dBi antenna, which means it can transmit and receive signals over a longer distance or with stronger signal strength. So, in general, 5 dBi is better than 3 dBi for extended range.
How far can a 5 dBi antenna go in meters? The range of a 5 dBi antenna depends on various factors, including frequency, power, and terrain. As a rough estimation, a 5 dBi antenna can reach several hundred meters to a few kilometers in typical conditions.
How far can a 12 dBi antenna range? A 12 dBi antenna can have a significant range, potentially reaching several kilometers to tens of kilometers in line-of-sight conditions, depending on other factors like frequency and power.
How far off the ground should an antenna be? The optimal height for an antenna above the ground depends on its type and purpose. For example, a VHF/UHF antenna for mobile communication might be mounted a few meters above the ground on a vehicle. A general guideline is to keep antennas as high as practical while considering factors like safety and local regulations.
What is the best distance between antennas? The best distance between antennas depends on the specific application and the type of antennas used. In many cases, antennas should be spaced at least half a wavelength apart to minimize interference. However, for precise guidance, consult the antenna manufacturer’s recommendations or antenna design guidelines.
What is the minimum spacing between antennas? The minimum spacing between antennas depends on their operating frequencies and the desired level of isolation. Generally, spacing antennas at least half a wavelength apart is a common guideline to avoid interference.
What is the rule of thumb for antennas? A rule of thumb for antennas is to match the antenna’s length or dimensions to the wavelength of the operating frequency. Additionally, antenna height, placement, and orientation are critical factors for optimal performance.
Does cable length affect antenna? Yes, the length and quality of the cable connecting an antenna to the transmitter or receiver can affect antenna performance. Longer cable lengths can result in signal loss, so it’s essential to choose an appropriate cable type and length for your setup.
Does a longer antenna get better reception? Not necessarily. The length of an antenna should be matched to the wavelength of the desired frequency for optimal reception. Longer antennas are more suitable for lower frequencies, while shorter antennas work better for higher frequencies.
What are the disadvantages of a folded dipole antenna? Disadvantages of folded dipole antennas include their larger physical size compared to some other antenna types, which may be impractical in certain installations. They may also have slightly reduced gain compared to other designs.
What is the major advantage of a folded dipole antenna? The major advantage of a folded dipole antenna is its wider bandwidth compared to a standard dipole. It can operate effectively over a broader range of frequencies.
What are the benefits of a folded dipole? Benefits of folded dipole antennas include improved impedance matching, reduced sensitivity to nearby objects, and a wider bandwidth compared to standard dipoles.
How to design a folded dipole antenna? Designing a folded dipole antenna involves calculating its length based on the desired operating frequency and impedance matching requirements. You’ll also need to consider the spacing and dimensions of the folded elements.
What is the bandwidth of a folded dipole antenna? The bandwidth of a folded dipole antenna can vary depending on its design and dimensions. However, folded dipoles are known for their broader bandwidth compared to standard dipoles.
Which folded dipole antenna is used for VHF? Folded dipole antennas are commonly used for VHF (Very High Frequency) applications due to their ability to provide good performance in this frequency range.
Is a loop antenna better than a dipole? Loop antennas and dipole antennas each have their advantages and disadvantages. The choice between them depends on the specific application and requirements. Loop antennas can be more compact and have some directional properties, while dipoles are simpler to construct and are often used for omnidirectional coverage.
How do I increase my dipole antenna gain? To increase the gain of a dipole antenna, you can:
- Lengthen the antenna: Make it a full-wave or multi-wave dipole for higher gain.
- Add directors or reflectors: Create a directional Yagi-Uda or log-periodic antenna.
- Increase the antenna’s height above the ground.
- Use an antenna tuner to optimize impedance matching.
- Choose materials and construction techniques that minimize losses.
How much gain can you get out of a typical dipole antenna? A typical dipole antenna has a gain of approximately 2.15 dBi, which is isotropic gain. By adding elements like reflectors and directors, you can achieve higher directional gains.
Can a dipole antenna be too high? In general, a dipole antenna can be positioned at various heights, but there isn’t a single “too high” height. The optimal height depends on factors such as frequency, radiation pattern, and desired coverage area. However, extremely high placement might introduce additional challenges in terms of structural stability and safety.
What is the best angle for a dipole antenna? The best angle for a dipole antenna is typically horizontal or perpendicular to the ground for omnidirectional radiation. However, for specific directional patterns, such as vertical polarization, the angle can vary based on your goals.
What is the best wire for a dipole antenna? Copper or aluminum wire is commonly used for dipole antennas due to their conductivity. The wire gauge or thickness should be chosen based on the antenna’s power handling requirements and mechanical strength.
How high should a 40-meter dipole be? For a 40-meter dipole antenna, the ideal height above the ground is generally around 20 to 50 feet (6 to 15 meters) to achieve good radiation efficiency and coverage.
What is the best height for a dipole? The best height for a dipole antenna depends on the desired operating frequency and specific requirements. In general, a height of at least a half-wavelength above the ground is a good starting point for improved performance.
Which is more important, grounding or bonding? Both grounding and bonding are important in electrical and RF systems, but they serve different purposes. Grounding provides safety by connecting equipment to a common electrical ground, while bonding ensures electrical continuity between various parts of a system to prevent differences in potential.
Does a dipole need a counterpoise? Dipole antennas do not typically require a counterpoise, as they are often used as balanced antennas. However, a counterpoise can be beneficial in certain situations, such as when a ground plane is needed for a vertical dipole.
What does a 49-to-1 balun do? A 49-to-1 balun is a type of impedance transformer that matches a 49-ohm unbalanced feedline to a 1-ohm balanced antenna system. It is often used in specific antenna configurations or for impedance matching purposes.
Does a dipole need an RF choke? A dipole antenna does not always require an RF choke, but one may be added to prevent common mode currents on the feedline. An RF choke can help reduce RF interference and improve antenna performance.
Is “2 fold” the same as 200%? Yes, “2 fold” is the same as 200%. It means doubling the original quantity or size.
What does a fold change of 0.5 mean? A fold change of 0.5 means reducing the original quantity or size by half. It is equivalent to a 50% decrease.
Is “3 fold” the same as “3 times”? Yes, “3 fold” and “3 times” are equivalent and mean tripling the original quantity or size.
Does “4 fold” mean 400%? No, “4 fold” does not mean 400%. It means quadrupling the original quantity or size, which is equivalent to a 300% increase.
Does “10 fold” mean 10x? Yes, “10 fold” means increasing the original quantity or size by a factor of 10, which is the same as 10x.
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