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This calculator is designed to give the vertical length (height) of a quarter wave ground plane antenna, and the length of each of the four radials (often called radiators) for the frequency chosen. The normal quarter wave ground plane antenna consists of a vertical radiator which is insulated and centered between 4 horizontal surrounding. Microstrip Calculator. Pasternack's Microstrip Calculator computes a microstrip's height/width ratio, impedance and relative dielectric constant for a microstrip transmission line. Bookmark or 'Favorite' this microstrip line impedance calculator page by pressing CTRL + D. We can provide you with comprehensive Subwoofer Box Calculator for online creating a high performance subwoofer enclosure. Build a ported box, sealed box for your low-frequency speaker. Make a subwoofer enclosure plan. Calculate a speaker box volume, port length and other parameters without getting confused in formulas. Overview: This is a calculator for designing a 1/4 Wave Flared Vent T-Line/Horn/Bass Reflex Enclosure. The formulas used in the calculator create a design that suggests the most maximally flat response in an anechoic environment based on the number of drivers, the thiele small parameters and the allotted dimensions specified in the user’s input fields.Continue reading →.

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First described by Paul Voigt in 1930, TQWTs allow a good quality-to-price ratio. They are also easy to build.

Similar to transmission lines, the TQWT is different by its shape, a kind of horn is used as back load but the driver is not placed at the beginning of the cone as usual but on its side.
The port is used to adjust the rear flow according to the driver type, internal damping and desired response.
The resonance frequency depends only on the length L of the cone and the driver position is calculated by the formula indicated on the schematic.
During the tune-up, it's a good idea not to close definetely a side of the box to allow an easy modification of the internal damping.
The height of the port should also be adjusted through both measurements and listening sessions.

It's not advisable to select a very low frequency cutoff as a not very refined bass could be obtained.

Ground Plane Antenna Calculator

Aus der welt der fkk jugend. The TQWT adapts very well to full-band drivers or bass-medium drivers of small dimensions.
The folded horn gives a very practical loudspeaker with a driver positioned at the right height without any support.

Example 1

Example for a 170mm driver. The lower cut-off is at 45Hz. May be enhanced with a tweeter and a simple passive crossover.

Example 2

Here is another version for smaller loudspeakers:

Example 3

Example using a 130mm driver like the Fostex FE127 but could use also smaller 100mm drivers like the Fostex FE103 or FE103 Sigma.

Example 4

By Gérard Chrétien, published in L'Audiophile # 38 (Spring 86).
It uses a Triangle T17FL (170mm) as woofer-medium and a tweeter Technics 5HH10.
As the T17FL is no longer available, you can replace it by a Triangle TP16PP122o (Fs=53Hz, 92dB).
The tweeter can be replaced by the Triangle TZ20 (93dB) with probably no resistive network.

Schematic

Filter

This very simple filter operates at 8KHz/6dB and the level of the tweeter is reduced by around 5dB to match the woofer.

Damping

A big work was done to obtain the best damping.

During the damping tuning a side is not definetely closed.

Other Photos

The loudspeaker (nearly) finished.

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The following program will calculate the lengths needed to construct several popular wire antennas. All you need to do is enter the desired resonant (center) frequency in the form below, then click 'Calculate'. The correct lengths for the various models will be displayed in the chart. (To better understand the variables be sure to read the application notes and study the drawings, following.) This calculator will accurately compute values for all HF antennas — 1.8 - 30 mHz.

The basic formula for determining the length of a center fed, half-wave wire Dipole or Inverted Vee antenna is:

468 ÷ freq (mHz) = Length (feet).

This formula takes into consideration the capacitive 'end-effect' from insulators which shortens the physical length requirement for the equivalent electrical length. The inverted Vee antenna will be shorter by 2 - 5% depending on the angle from horizontal.

Half-wave Flat Top Dipole

Half-wave Inverted Vee Dipole

The feedpoint impedance of a Dipole in free space is close to 75Ω. Dipoles can be fed directly with 50Ω or 75Ω coax, or with a 1:1 balun at the feedpoint. The slight mismatch when using 50Ω coax can be easily matched with an antenna tuner. More importantly, for symmetrical current distribution, reduced feedline radiation, and thus a cleaner pattern, a balun should always be used at the feedpoint.

Due to the proximity to ground at the end of each leg, the feedpoint impedance of an Inverted Vee is very close to 50Ω. Inverted Vees thus can be fed with 50Ω coaxial cable, with or without a 1:1 balun. (The advice regarding the use a feedpoint balun pertains to the Inverted Vee as well.)

Both Dipoles and Inverted Vees can be fed with 300Ω or 450Ω ladder or open wire feeders into a balanced Antenna Tuner. This configuration, known as a 'Doublet', will work well as a multiband antenna.

Flat-Top Dipole or Inverted Vee? As is often the case when given a choice, there are trade-offs involved. The Inverted-Vee requires only one tall support, and less horizontal spread than the Flat-Top Dipole. It is also a very close match to 50 Ω coax. On the other hand there is some loss of gain because the pattern is less directional, and the bandwidth is narrower than the the horizontal dipole.

CONSTRUCTION NOTES: Half-wave Dipoles and Inverted Vees are very easy to construct, and are great for homebrew projects. You may purchase commercially made end insulators and center insulators with coax connectors built in, but why not make it truly homebrew and make your own hardware? It is quite easy using schedule 40 PVC pipe. Admittedly, if you are going to use a balun at the feedpoint, purchasing a center insulator with the balun built in is certainly a lot less work!

If you decide to roll your own, be sure all connections are secure, both mechanically and electrically. Be sure to properly solder all joints and to use weatherproofing. Remember to provide some type of strain relief at the center insulator for your 'dangling' feedline. Not only does the feedline represent a strong downward tug, but when the wind blows the mechanical stress on your connections increases dramatically. A good strain relief system is to wrap the feed cable once around the center insulator and secure it with 'UV-Resistant' (usually black) tie-wraps. You will, of course 'invent' something much more sophisticated for your design!

Suitable feedline can be 50 Ω coax, such as RG-58, RG-8X, RG-8, RG-213, or 75 Ω types such as RG-11, RG-59, RG-6, or even 75 ohm twin lead. Believe it or not, even zip cord (lamp cord) will perform quite well. Of course you need to 'size' your feedline according to the power you intend to run. Power in excess of 200 watts can develop very high RF voltages. Be sure your feedlines and antenna hardware can handle the power.

In the real world — where you build your antennas — the actual impedance of your wire antennas will depend on several variables. i.e. height above ground, proximity to large, especially metalic, objects, and proximity to other resonnant antennas. Always cut your antenna lengths a bit long. This will allow you to 'fine tune' the antenna by trimming. You will quickly learn that 'trimming' is a LOT easier than 'adding to'!

When you decide where to 'hang' your antenna, remember that the horizontal radiation pattern of a Dipole in free space is a wide 'Figure-8', which radiates perpendic

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