# BookRiff

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## What is beta matching?

The Beta or Hairpin Match is a simple and robust form of matching a lower impedance Yagi to the transmission line. The system operates by shortening the DE so that the parallel equivalent impedance at the DE terminals is the desired load resistance in shunt with some capacitive reactance.

## What is a gamma match?

A gamma match is an adjustable device used for feeding and matching an antenna, coupled to the driven element of a beam to match the 50 ohm coaxial feed-line. It forms together with the main radiating element a closed wire stub, adding inductance to the antenna input impedance.

## What does front to back ratio mean in reference to a Yagi antenna?

The “front-to-back ratio” in reference to a Yagi antenna is the power radiated in the major radiation lobe compared to the power radiated in exactly the opposite direction.

## How does an antenna gamma match work?

A gamma-match serves a triple purpose: As a small diameter wire parallel and in close vicinity with the main radiating element, it will carry only a fraction of the main element current while being exposed to the same electrical field strength.

## What is the impedance of a Yagi antenna?

In most antenna designs, the feedline impedance will be 50 ohms, but usually the feed point impedance of the Yagi is rarely 50 ohms. In most cases it can vary from approximately 40 ohms to around 10 ohms, depending upon the number of elements, their spacing and the antenna’s pattern bandwidth.

## Why does Yagi have folded dipole?

The folded dipole is a standard approach to increasing the Yagi impedance. It is widely used on Yagi antennas including the television and broadcast FM antennas. The simple folded dipole provides an increase in impedance by a factor of four.

## How is gamma match calculated?

If you want to do it with a pencil and paper, you can use this formula to calculate the dimensions: Gamma rod length = 0.04 – 0.05 wavelength. Gamma rod diameter = approx 1/3 – 1/2 the element diameter. Gamma rod spacing = approx 0.007 wavelength.

## What is side lobe level?

Sidelobe Level is information how large (or small) are side lobes in the radiation pattern of an antenna. So for example, if SLL has the value of -20 dB, it means that the maximum level of side lobes in the radiation characteristic is attenuated by 20 dB, compared to the main beam.

## How do you adjust a gamma match?

Set the frequency in the middle of the band and adjust the capacitor to give the lowest s.w.r. Then, run a series of checks across the band to find the resonant point of the beam. If that point is not where you want it, either lengthen or shorten the driven element. Leave the parasitic elements as they are.

## What is a folded dipole?

: an antenna in the form of an elongated horizontal loop resembling a dipole in appearance with connections at the middle of one or both of the two parallel sides.

## Does a folded dipole need a balun?

No balun required – unbalanced coax all the way to the feedpoint, with guaranteed symmetrical excitation. Easier to waterproof the feed, as the connections are inside, and you can heatshrink over the feedpoint. Only one side of the dipole touches anything, the other just hangs open.

## Which is the best definition of dipole 1A?

Definition of dipole 1a : a pair of equal and opposite electric charges or magnetic poles of opposite sign separated especially by a small distance b : a body or system (such as a molecule) having such charges or poles

## What is the meaning of the word di pole?

di·​pole | \\ ˈdī-ˌpōl \\. 1a : a pair of equal and opposite electric charges or magnetic poles of opposite sign separated especially by a small distance.

## What kind of dipoles have positive and negative charges?

There are two types of dipoles — electric dipoles and magnetic dipoles. An electric dipole occurs when positive and negative charges (like a proton and an electron or a cation and an anion) are separate from each other.

## Can a beta match be used for a hairpin match?

(Multiple wrong values of current and its distribution get magnified.) But the point is that there IS a difference, contrary to some claiming that it IS NOT. The net result is that Beta or hairpin match can be used to find the match of antenna to the feedline at the expense of some loss of efficiency.