# Labs from YSI 95 : Transmitter Hunt.

Chris Knox
CARA Yerkes Summer Institute, August 1995

This is the staff copy of the lab.

## Objectives:

• For the students to learn the basic concepts about radio transmitters and receivers through the use of physics and algebra\trigonometry.
• To learn more about the transmission of wave lengths and how to calculate the actual wavelength of a transmission.
• To be able to show how polarization is important and the affects it has on FM band frequencies.
• To introduce the attenuate to the students, find out why body fading works, and why it is important in radio hunting.
• Also to experimentally see which method of radio hunting works best by observing and watching the teams work together to find the transmitter.

## Materials:

### Transmitter

1. FM stereo transmitter kit
2. Hallmark card digital voice recorder
3. Lantern Battery
4. NE555 timing chip\circuit
6. UHF TV antenna ears
7. Card board box

### Attenuater

1. Aluminum foil
2. Paste board or cardboard tube

### Concepts:

Polarization - the electrons in light emit classical electromagnetic waves, just as if the atoms were a little radio antenna. The more direct light causes the receiver when placed in "hot spots" to have a stronger and clearer signal. If placed in "cold spots" where there is little light the signal might appear weaker.

hot spot - place where there is a large accumulation of atoms.
cold spot - place where there is a small accumulation of atoms.
Wavelength - calculate using f(wavelength) = c

### Procedure:

A small exercise was developed from a game the HAMs use called Fox Hunt. This idea enabled us to put together an exercise where students could have fun learning about transmitters and radio waves. First the students will be given an introduction about the basic concepts of radio waves. Then they will be given a parameter in which the radio is located to prevent them from getting lost. The radio transmitter will be placed in the front lawn of the Yerkes Observatory, hidden and known only to the teacher and the teachers assistant. The best place found was near trees to the east of the front lawn. The students will be given little hand held FM radios, an attenuate, and the frequency the transmitter will be transmitting on. The students will be observed by time and technique. This will allow us to see what works best since the students will be in teams of two.

### Analysis:

The first group of students were broken into twos and team 1 found the transmitter in 12 minutes but by looking at the trees for it and not using the attenuater very much. This was a common response among the students because two of the other teams responded similarly. It was also found that the teams watched each other as they looked for the transmitter to see where they went to help them with there search. The attenuater worked great. Two out of the three who used it found the transmitter within 12 minutes.

Important Disclaimers and Caveats: