HAM/Howard Community College/Fall 2011/550 BH^2 V2
Electronic Sections Expected
Design and build a field expedient dipole antenna from rudimentary parts, such as wire, string and ceramic insulators and continue to to improve the foxhole radio
The HAMV2 project was a continuation of the HAM project started by the majority of the HAM (BH^2) team members. HAMV2 was designed to build on what was accomplished earlier. The focus of our project was to design and build a dipole antenna at the least cost. Using equipment that was donated to us we were able to construct a dipole antenna capable of transmitting in the 7.50MHz range. We culminated our project with a visit to the National Electronics Museum. It was amazing to see how much the study of electronics has evolved since the days of Maxwell, Hertz, and other theoretical physicist. A week by week summary of our progress can be viewed by accessing our Weekly Reports page.
We decided to continue with our HAM project. At the start of this project john planned to continue to work on the fox hole radio and attempt to add some modifications to the setup to get it working. Team member FAB planned to work on building a low power 30 MHz transceiver matching dipole. The two of us also went through and picked out parts from the stuff that Dave donated to us during our first project. John found some interesting circuitry that he thought he could use to help in the foxhole radio and team member FAB found parts that would help him build a dipole antenna.
John decided to rebuild the foxhole radio with some thicker wire to insure that everything was connected. Here is a picture of the Original foxhole radio from the first project and here is a video of the rebuilt foxhole radio. This video is also a test of the foxhole radio. He decided to change the ground and speaker used for this test. The ground used was an electrical ground found in a wall plug. The speaker system used had an amplifier in it in hopes that it would make it a lot easier to hear the radio signal. While testing John was able to hear static from the radio however no signal could be heard. The final attempt to get the radio working was to add a Low Voltage Audio Amplifier Manual in between the detector and the headphone.
After testing this new setup, the same results happened from the first testing. No signals were picked up again.
Initially, team member FAB started to research what exactly was needed to build a low power 30 MHz transceiver matching dipole. However, after picking through the donated equipment, there were parts of antennas that would be used to help us learn about antennas and design a antenna and tutorial to help future project goers. There are pictures of two dipole antennas and an antenna made of slinkys. The first picture was one team member FAB completed during this project.
During class we got classmates to help us to measure the length of the dipole arms in order to calculate the targeted waved lengths that could be received. The copper dipole antenna had arm lengths of approximately 20 meters, while the other antenna had one arm of 31 meters. We found out that the second antenna was not a true dipole antenna. From our research we assumed that the dipole antenna was a half wavelength dipole antenna. From this team member FAB used c = λʄ ,where c is the speed of light, λ is the wavelength and ʄ is the frequency, to determine the targeted ʄ of this antenna. The antenna was calculated to transmit and receiver in the 7.5 MHz range. the testing of this antenna could not really be done do to the lack of radio equipment.
Here are some files that team member FAB found to help understand antennas
Finally, team member FAB brought to attention the idea of a field trip to the National Electronic Museum in Linthicum Maryland right by BWI airport. We both decided to go and explore what it had to offer. It was a great experience for any electrical/electronic enthusiast. They had 12 different exhibits which included : Fundamentals, Communications, Early radars, Cold War radars, Modern radar, Countermeasures, Under Sea, Electro-Optical, Space Sensor, Past, Web and WWII radar exhibits. Here is the link to the museum's website Below is a presentation that John put together of our visit to the museum.
We used a decision tree to assist us in making decision on key points during project development. The decision tree consists of four pages that highlights key decision points during our project development. Click below to view decision tree:
- Week 0
- Our group decided to focus on building solely a dipole antenna instead of a dipole antenna and 30MHz transceiver.
- We agreed to make an attempt to improve the foxhole radio with some of the components received from CARA.
- We agreed to focus on the theory behind signals transmission and how radio waves propagate throughout the environment.
- Week 1
- We decided to focus on building the dipole antenna. No more work will be done on the foxhole radio.
- We also agreed on taking a practical approach to our project. Instead of trying to teach the the theory of our project, we will just show the practical applications of an antenna.
- We are going to try to end the project early. We have accumulated enough points to pass. We need to focus on other projects.
- Week 2
- We will be going to the National Electronics Museum on Saturday. We will present the results of our field trip to the class the week of 31 October 2011.
- We will end the project after week three.
- Week 3
- Assign tasks for last week's presentation.
- Project complete. Ask instructor to grade.( so we thought)
- Decided to continue to week four of ham project
- Week 4
- No significant decisions to report.
All materials used to construct our antenna was donated by the Columbia Amateur Radio Association.
- 200' of 14 gauge wire
- Ceramic insulators
- 75 ohm cable
- Support wire to secure antenna
- Admission fee to National Electronics Museum - $6.00.
- Our team used Microsoft's Office Suite for word processing, spreadsheets creation, and and word processing.
- Google Docs (spreadsheet and presentation)
- AutoCad Architecture Student Version
- Autodesk 123D (Schematic)
Click on the link 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.
Here is a link to our tutorial on how to build a simple Dipole Antenna
- Replace receiver with transceiver.
- The cable in our drawing is a 75ohm cable
- Our team succeeded in developing a tutorial for anyone interested in building a dipole antenna that can be used to transmit in the 7.50MHz frequency range. The tutorial along with the other resources listed in the Story section should be enough to successfully construct an operational dipole antenna of any frequency under 30MHz.
- Next big step for HAM project at HCC will be to get equipment and a licensed operator in order to start a broadcasting center at HCC.