HAM/Howard Community College/Fall 2011/501 Veteran Bacon

Problem Statement

We will build a ham radio, become licensed to use it, and broadcast.

Team Members

Summary

We began our project believing that we could accomplish our goal using an ELENCO model AM/FM-108K radio kit. After determining it wouldn't work for our purposes, we resolved to build our own radio from scratch using foxhole radios as a model. We were able to assemble the radio and at times hear a faint popping sound, however no intelligible transmission was ever picked up, nor were we able to broadcast from the radio.

Poster

The three primary components of the foxhole-style radio.

Story

We located the ELENCO radio kits in the Engineering classroom, and resolved to set it up. As it was already mostly assembled, it simply required the addition of a 9V battery and earphones. After plugging those two pieces in, we tested all seven radios by tuning them to FM 101.1 and identified two of the radios whose dials were most accurately calibrated and whose volume was the loudest (radio kits #2 and #5).

We then read up on broadcasting and Ham licensing. Realizing that the accepted range for a beginner-level operator was 50-54 MHz and that the ELENCO only functions in the FM band (88-108 MHz), we decided to switch our focus to construction our own radio, whose frequency range we could determine ourselves. This video became the basis of our new model.

We clipped the head off of a coat hanger and straightened it out to serve as the radio antenna. The inductor was made by spooling 24 AWG wire around a toilet paper tube 101 times. A razor blade was blued with a blow torch and a pencil was snapped in half to make the detector. We then stripped different segments of wire to connect all the components and attached them to a wooden board using thumbtacks. The headphones we originally attempted to splice into the circuit were USB and proved too difficult to manage. For a ground we used a sink in the Engineering room, but we did not receive any signal.

Replacing the headphones with a simpler model, we decided to measure the connectivity between all the components using the OHM function of a multimeter. All connections tested positive for connectivity. Rather than using metal piping as a ground, this time we used the ground on an electrical component test bench. We tested the radio again and this time received a small amount of static through the headphones.

Material List

Final Radio

Wooden block
Razor blade
Pencil
24 AWG wire
Coat hangar
Cardboard tube
Thumbtacks
Paperclips
Headphones
Multimeter
Test bench

Original Radio

ELENCO radio kits
9V batteries
Headphones

Time

We spent 27 hours on this project.

Next Steps

The small static sound confirms that the radio was properly connected, but still needs some tuning. To tune the radio we will have to add more spools in the inductor. 120 spools should put the radio somewhere in the medium wave AM band (.5-1.6 MHz). To legally broadcast, it will also be necessary to pass the FCC's "Technician" test, for which you can register here. A list of all possible test questions can be found here.