SOUTH BALDWIN AMATEUR RADIO CLUB - SBARC
PROJECTS AND EXPERIMENTS
JANUARY 2017 - WSPR
WSPR (pronounced "whisper") stands for "Weak Signal Propagation Reporter". It is a computer program used for weak-signal radio communication between amateur radio operators. The program was initially written by Joe Taylor, K1JT, but is now open source and is developed by a small team. The program is designed for sending and receiving low-power transmissions to test propagation paths on the MF and HF bands. These low power transmissions can be as low as 200 milli watts, or lower. Radio beacon transmissions have been sent out from the United States and heard all around the world - on less than a watt of radio frequency power.
The SBARC amateur radio club has been experimenting with a locally designed and built digital transmitter on a PC board device that couples with a Raspberry Pi, a single-board computer developed in the United Kingdom by the Raspberry Pi Foundation to promote the teaching of basic computer science in schools and in developing countries. Using the Raspberry Pi and our home brew transmitter combination, the members of the club have been able to successfully transmit a beacon signal at very low wattage, and be heard all over the North American continent and parts of Europe.
The Raspberry Pi 3.0 device gets its power from a 2 watt USB power supply and supports and additional 4 USB slots. It also supports an Ethernet port and a micro SD slot so that additional software can be made available to the device's built in control software.
The home brew device is a circuit board (pcb) that plugs into the rPi 40-pin header. It boosts the signal level to about 200 mW and contains a seven pole low pass filter to keep out-of-band transmissions down by 45 dB. It also contains an LED the lights when transmitting and a crude output power indicator.
February 2017 - Amateur Radio Emergency Date Network - AREDN
"An Amateur Radio Emergency Data Network (AREDN™) is a high speed data network built with Amateur Radio Operators and Emergency Communications Infrastructure in mind.
AREDN™ is self-configuring and self-healing. Where possible, AREDN™ will establish connections with as many other AREDN™ compatible devices (nodes) as possible and form a redundant mesh like network.
AREDN™ nodes automatically finds the “most reliable” nodes (greatest chance of success on packet delivery) to attempt delivery of the packets sent across the network. One need not know the exact path to get to the destination, only to know what the destination is."
From the national AREDN website: http://www.aredn.org
An AREDN mesh network is an implementation of a wireless data networks over amateur radio frequencies using commercial off-the-shelf (COTS) hardware such as 802.11 access points and D-STAR equipment. Only licensed amateur radio operators may use amplifiers and specialized antennas to increase the power and coverage of the 802.11 signal.
The SBARC amateur radio club has worked hard with other hams in Mobile and Baldwin County to establish a multi-node mesh network that will support an emergency communications network, should such be needed.
On a recent Saturday morning, some of the SBARC members met at the Lake Forest Yacht Club parking lot to setup a portable 40 ' mast which supported a high gain AREDN antenna. With the antenna connected to a laptop so as to monitor the access point's built in software, the group was able to connect to and see nearby nodes on the AREDN network.
APRIL 2017 - Home made Mag Loop
A new project for the club in April is the attempt by Bruce Raymond to build a Mag Loop antenna that could be used on 30M. See below picture. Bruce has been working with other members of the club to tune and test the antenna.
Bruce tells us that he's been trying to create a Mag (magnetic) loop antenna for several years. The loop is 3 ft in diameter and will hopefully work on 30m. The basic antenna is made out of plastic pipe and 1/4” copper tubing. Bruce is still working on the approach to feed the antenna. The piece of wood at the bottom of the antenna sitting on the floor has a variable capacitor, potentiometer, and eventually a motor to adjust the capacitor mounted on it. Mag loop antennas are kind of fascinating because they have such a small footprint compared to, well just about any other type of antenna. For instance, a 30m dipole is 46 ft long. Not a bad reduction if I can use the mag loop instead of the dipole.
You’re supposed to be able to receive and transmit using a Mag loop. The gotcha is that the antenna has a very narrow bandwidth, which could be a good thing. After all, it should reject all signals that are not within the bandwidth, making it very quiet on receive. Follow up with us in a month or two and see how this project is progressing. ___Joe McIntosh, SBARC secretary.