VHF Radio Experiment: Testing Antennas & Polarization

In summary, the conversation is about a physics class experiment involving radio waves. The experiment will test the field strength of different antennas and the effects of vertical and horizontal polarization on the field strength. The aim is to produce data and graphs that can explain how angles of radiation affect directivity and gain. The person conducting the experiment is a licensed ham operator and will transmit at 25 Watts. They are also considering building the antennas themselves or using wire. Suggestions or advice for the experiment are welcomed. It is important to make sure the experiment does not violate any radio laws and avoid multipath effects.
  • #1
prime-factor
77
0
Hi. I have been assigned the task of designing an interesting experiment involving waves of any kind for physics class. I have chosen to focus on radio waves for my experiment and this is the basis of it:

Three antenna's will be tested for point to point transmission (VHF): [ 144 MHz ]

>>3/4 Wave antenna

>>1/4 Wave antenna

>>5/8 Antenna (Best Angle of Radiation Usually)

These antennas will be connected to a VHF radio transceiver, a voice signal will be transmitted and this will be measured with a field strength meter. The purpose of the experiment is to test whether vertical polarization vs horizontal polarization will make a large difference in field strength. (basically testing antenna up straight and then again when horizontally polarized and looking for differences in field strength).

My aim is to produce data which can be graphed illustrating the differences in field strength based on the different antennas as well as the polarization differences. I am hoping that this can lead on to an explanation of how angles of radiation affect directivity and gain.

Also I am wondering whether to build the antenna's professionally (I have the equipment to do so), or to demonstrate the simplicity and to simply use wire. (The reason I have chosen these antennas is because they are the types that will match my transciever impedance)

Any suggestions/help/advice are NEEDED!, I would highly appreciate it.
 
Physics news on Phys.org
  • #2
How much power are you planning to transmit at?

Radio frequencies are assigned differently in different countries. In the case of US and Canada, 114 MHZ is an Amateur radio band of 2 Meters. If you transmit with more power than allowed, you need a Radio licience and you have to have your radio tuned so you don’t interfer with someone else’s radio or TV etc.

If this is a school project you should check with your teacher to make sure you will not violate any radio laws.
 
  • #3
I am a fully licensed ham operator (Advanced Open License) in Australia. I am going to transmit at 25 Watts. In Australia 144 -148 MHz is the amateur VHF band and 25 Watts is well within the limit :) .
 
  • #4
Also make sure there are no multipath effects. I was once testing transmitters (390 MHz) in an open field and there was one spot where I couldn't pick up any signal from them. It turned out to be multipath from a three strand barbed wire fence about 70 ft. from the transmitter.

https://www.physicsforums.com/showthread.php?t=283466&highlight=antenna
 

Related to VHF Radio Experiment: Testing Antennas & Polarization

1. What is VHF radio?

VHF stands for Very High Frequency and is a range of radio frequencies commonly used for communication. It typically refers to the frequency range of 30-300 MHz.

2. What is the purpose of a VHF radio experiment?

The purpose of a VHF radio experiment is to test the performance of different antennas and polarization techniques in order to optimize communication and transmission of signals.

3. What is antenna polarization and why is it important?

Antenna polarization refers to the orientation of the electric field of an antenna. It is important because it affects the direction and strength of the radio waves being transmitted and received, and can significantly impact the quality of communication.

4. How is antenna polarization tested in a VHF radio experiment?

In a VHF radio experiment, antenna polarization is tested by rotating the antenna and measuring the signal strength and quality at different angles. This can be done by using a signal strength meter or by analyzing received signals using specialized software.

5. What are some common types of VHF antennas used in experiments?

Some common types of VHF antennas used in experiments include dipole antennas, Yagi antennas, and helical antennas. Each type has its own advantages and disadvantages, and the best choice will depend on the specific needs and goals of the experiment.

Similar threads

  • Introductory Physics Homework Help
Replies
11
Views
1K
  • Introductory Physics Homework Help
Replies
6
Views
4K
  • Electrical Engineering
Replies
4
Views
1K
Replies
10
Views
809
Replies
41
Views
4K
Replies
6
Views
387
Replies
24
Views
1K
Replies
4
Views
900
  • Introductory Physics Homework Help
Replies
2
Views
1K
Replies
14
Views
2K
Back
Top