why

hiyan

Joined Sep 23, 2005
26
i wantto ask why we take Antenna length lemda/2 and lemda/4?

2nd in the end of antenna why resiatnace high?

3rd length of transmission line is depends on the wavelength of the signal being transmitted why?

4th how the standing waves are genrated in transmission line?

i hope all members who know guide me and explain me briefly.thanks

beenthere

Joined Apr 20, 2004
15,819
Hi,

I think if you do some looking on the topic of resonance, most of your questions will be answered. All the things you mention have to resonate at the transmit/receive frequency in order to function efficiently. A little antenna theory will explain why quarter- and half-wave antennas work.

hiyan

Joined Sep 23, 2005
26
Originally posted by beenthere@Dec 7 2005, 10:24 PM
Hi,

I think if you do some looking on the topic of resonance, most of your questions will be answered. All the things you mention have to resonate at the transmit/receive frequency in order to function efficiently. A little antenna theory will explain why quarter- and half-wave antennas work.
[post=12291]Quoted post[/post]​

JoeJester

Joined Apr 26, 2005
4,390
Visit http://www.phy.davidson.edu/instrumentation/NEETS.htm

Module 10 - Introduction to Wave Propagation, Transmission Lines and Antennas, presents the characteristics of wave propagation, transmission lines, and antennas.

n9xv

Joined Jan 18, 2005
329
"i wantto ask why we take Antenna length lemda/2 and lemda/4?"

Lamda/2 & Lamda/4 denote the physical half-wave & quarter-wave dimensions for the antenna in question. The quarter-wave antenna is the building block from which all antenna systems are designed.

The half-wave antenna is the fundamental design by which all antennas are ultimately compared.

"2nd in the end of antenna why resiatnace high?"

In a half-wave antenna, the current nodes are at minimum towards the ends of the antenna. Thus, minimum current = highest impedance.

"3rd length of transmission line is depends on the wavelength of the signal being transmitted why?"

This is due to velocity factor. In other words, the speed of electricity is slower through any "medium" than it is through a vacuum.

"4th how the standing waves are genrated in transmission line?"

Standing waves or standing wave ratio (SWR) is due to an impedance mismatch between feedline and antenna. Standing waves are the waves or energy reflected back towards the transmitter due to the mismatch. Standing waves are the "leftover" waves that did'nt get transmitted or radiated.

hiyan

Joined Sep 23, 2005
26
Originally posted by n9xv@Dec 11 2005, 11:59 AM
"i wantto ask why we take Antenna length lemda/2 and lemda/4?"

Lamda/2 & Lamda/4 denote the physical half-wave & quarter-wave dimensions for the antenna in question. The quarter-wave antenna is the building block from which all antenna systems are designed.

The half-wave antenna is the fundamental design by which all antennas are ultimately compared.
"2nd in the end of antenna why resiatnace high?"

In a half-wave antenna, the current nodes are at minimum towards the ends of the antenna. Thus, minimum current = highest impedance.

"3rd length of transmission line is depends on the wavelength of the signal being transmitted why?"

This is due to velocity factor. In other words, the speed of electricity is slower through any "medium" than it is through a vacuum.

"4th how the standing waves are genrated in transmission line?"

Standing waves or standing wave ratio (SWR) is due to an impedance mismatch between feedline and antenna. Standing waves are the waves or energy reflected back towards the transmitter due to the mismatch. Standing waves are the "leftover" waves that did'nt get transmitted or radiated.
[post=12380]Quoted post[/post]​

Thank u all