HAM/Howard Community College/Fall 2011/550 BH^2

Electronic Sections Expected

Problem Statement

Construct a transceiver from off-the-shelf parts to communicate with local HAM stations. Construct a foxhole radio.

Team Members

FAB

RH

JH

Summary

Weekly Reports

The goal of this project was to build a radio transceiver either from electronic parts purchased at a electronic store or using a kit that could be purchased from e-retailers. Due to issues with importing electronics from outside the U.S., we instead chose to start at the basics of HAM radio and build a Foxhole Radio (FHR), a simple crystal radio that receives only but demonstrates the basic theory of radio design.

Poster

Story

Initially, John and Rhea had chosen the project as they wanted to modify a router's software and/or antenna to boost the signal range to create a super wifi hotspot. After discussing this over with FAB, the group decided to instead focus on building a transceiver. Each team member was assigned a different task for the weekend. These tasks included: research the science behind radios and radio waves, look for schematics, designs, or instructions on how to build a transceiver, and/or to research antenna design and theory.

Through our research we found out that in order to broadcast, we needed a member to have a FCC Technician license. We found information about what information we should know before taking the exam along with several practice tests. Attempting to build a radio transceiver from scratch proved ineffective as there was not a local store (Radio Shack) that sold the parts we would need but we did look into the possibility of purchasing kits from out of country. FAB discovered that the Columbia Amateur Radio Association (CARA) would be holding CARAfest which provided us with the opportunity to meet HAM radio operators, learn more about the history of HAM, real-world applications of HAM, and the general culture.

On the first weekend of October our group volunteered to help with setting up CARAfest. On Friday, FAB and John went to the Howard country fair grounds to help set up tables and mark off the parking lot with marked areas for people to setup stands. While there Dave Prestal, VP of CARA, gave a overview of what HAM is and what CARA does in the state of Maryland. He had a load of information that he gave to us. On Sunday the CARAfest was held. Our group went up and saw what was going on. There was free testing for one to try and get one of three licenses needed to start transmitting any signals. CARAfest was different then what we thought it may of been. While there were a lot of HAM members there walking around and all, all the stands that where setup were vendors. They sold everything, including components, cables, routers, tools, old equipment, antennas and other things that are used to run a HAM system.

In week 2, John brought in a pair of walkie talkies that we disassembled to learn about the circuitry and design. The disassembly was fairly simple and we attempted to boost the power by cutting the wires leading to the battery and connecting the leads to a external power source. On the first unit, this seemed to work after dialing in the voltage and current and we were able to hear static coming from the speaker, a good sign. While doing the same with the second unit using a second power supply, either too much voltage or current resulting in a loud popping noise which fried the unit. Before that, we were able to hear breaks in the static on the first unit when the second was transmitting. While John's voice did not come out of the first unit, we were able to transmit weakly with the second unit prior to it's death.

With links to a video on building a FHR and a PDF with a little more detail on constructing one, John built one himself out of everyday parts that one could find. The build was straight-forward but John was unable to get the unit to receive clearly which he believed to be the result of improper grounding. While we did not have the unit available to present to the class that week, we did present the findings we had made in regards to radio theory, design, and some photos of the FHR in progress.

Decision List

We used a decision tree to assist us in making decision on key points during project development. The file consists of six pages that highlight key decision points during our project development. Click below to view decision tree:

Week 1

Our group decided to focus on building a transceiver instead of working on trying to boost the range of a wireless router. We did not decide on the frequency range of the transceiver, because there was more research that we had to do.
Our group elected to build a dipole antenna instead of an inverted V. With the limited amount of time and resources, plus the complexity of the design of the inverted V, we decided to build the dipole antenna.

Week 2

Our team chose to build a transceiver only and drop the antenna portion of the project because of the complexity of the theory behind antenna design. The building of an antenna will be addressed if time permits.
FCC restrictions forced us to pursue amateur radio licensing. We would not be able to test the radio by transmitting without a valid license. We considered building a Faraday cage, but we decided to go with the license in case we wanted to field test the radio. The Faraday cage or a "dummy load" on the antenna would only work in a lab environment.
We also elected to build a Foxhole radio while we resolved the licensing issues.
After getting in contact with Columbia Amateur Radio Association (CARA) it was decided that our group would go and help with the CARAfest event hosted at the Howard country fair grounds. We were hoping to benefit from meeting club members. It turned out that this was a good idea because many of CARA's members are engineers.

Week 3

We elected to build a radio that works in the 30MHz range. Our decision is based on FCC restrictions and antenna design. To transmit in the 30MHz range all that is needed is a technician class license. The antenna design is is simpler also.
Who was going to pick up the equipment from Dave Prestal? Team member JH volunteered to pick the gear and store it bring it to the engineering classroom.
We decided to present often. We were leaving too many points on the table. After this week this has become an important part of our daily discussions.

Week 4

Decided to continue with the HAM project. Request made to instructor to keep same team members.
We worked out a schedule to edit the team page.

Material List

Price and locations of parts for Foxhole Radio

Inductor coil – Set of 3, Magnet wire 22g, 24g and 30g wire

Price: $7.39

Location: Radio Shack

Antenna – I used some old 25 foot Ethernet cable

Price: $18.57

Location: Radio Shack

Push pins (100 count)

Price: $6.49

Location: Wal-Mart

Paper Clips (100 count)

Price: $8.49

Location: Wal-Mart

Razor blades (10 count)

Price: $15.48

Location: Wal-Mart

2 Pencils (12 count)

Price: $5.47

Location: Wal-Mart

Left over toilet paper roll(cardboard portion)

Price - Varies depending on store and brand

Location any general store/grocery store

Holding board (piece of wood or hard cardboard)

Speaker/ Ear piece- this was a tough one to find. All searches for small speakers came up with shelf systems and car speakers. Need to find a component speaker

Software List

Our team used Microsoft's Office Suite for word processing, spreadsheets creation, and and word processing. In addition to basic document management creation one JH is receiving training on the following AutoCad products:

AutoCad Architecture Student Version
Autodesk 123D (Schematic)

Our team expects to benefit from this training next cycle. Our plan is to use AutoCad to create drawings that accurately represent our designs.

Time

Click on the icon to view a document that shows the amount of time invested by each team member. The times were pulled directly from each team member's personal logbook.

Tutorials

Foxhole radio Tutorial document links:

Finished FHR

Study Information for HAM test

Here are some files that Dave Prestal (VP of CARA) donated to the project to help study for the technician test. Going through these slide will help prepare one for the HAM test

Next Steps

Our team succeeded in developing a tutorial for anyone interested in testing for the FCC's technician class amateur radio test. The tutorial along with the pool of questions available from the Amateur Radio Relay League should be enough to successfully pass the technician license exam. Having a licensed team member is crucial during the testing phase of any radio design.

Our team successfully designed and built a foxhole radio (FHR) during this project cycle. The tutorial for the radio design can be found in the tutorial section. Groups desiring to build a FHR should use our tutorial and the websites we referenced in our individual pages.