About
I'm Steve Conklin, AI4QRFollowing
I’ve been thinking about how to optimize antennas for HF at my location, which is on a hillside. This provided me with some insight. I’m not sure what I’ll end up with for propagation to the East (over the hill), but to the West I can probably end up with very good results. Modeling will help. I’ll post more when I get to that.
On November 6th I’ll be helping Dave Freese, W1HKJ make a presentation about fldigi to the Huntsville Amateur Radio Club. Fldigi is an amazing open-source cross platform application for communicating using sound card digital modes on amateur radio.
Dave is really knowledgeable about the encoding and error correction used for the various modes, and I learned a lot by helping him with a similar presentation at the Huntsville Hamfest this year. Our demo was cross-platform between Windows and Ubuntu Linux.
There are some really interesting uses being made of fldigi and some companion applications - sending digital files error-free by amateur radio. This is useful for emergency communications in post-disaster situations, when information must be accurately transmitted. Some of these applications do not use point-to-point connections, and therefore allow a file to be received by multiple stations at once. That way, if any station fails to receive the file correctly, they can get a “fill” from any other station who did get it.
It’s possible to perform these file transfers simply by holding the microphone on an FM radio near the computer speaker, and to receive them with a computer microphone near the receiver!
This should be a worthwhile presentation for people with any level of interest or experience in digital sound card modes. For more information see Dave’s excellent web site. Don’t miss his sights and sounds of digital modes page, especially if you’ve been listening to the sounds on the ham bands and wondering what modes they are.
The presentation will be November 6th at 7:30 at the American Red Cross chapter house, 1101 Washington street, Huntsville, AL. This is the regular weekly meeting place and time of the Huntsville Amateur Radio Club.
Dave Freese, W1HKJ will be presenting a forum at the Huntsville Hamfest titled “Emergency Communications using HF Digital Modes”. Dave and a core group of contributors have been working for the last few years on a suite of open source applications for amateur radio. The fldigi application is the flagship of these.
Fldigi is a digital modem application which generates and decodes a number of digital modes using the sound hardware in your computer. Amateur radio using digital modes has been growing in popularity, and with good reason. These modes offer a variety of tradeoffs between rf bandwidth, data bitrate, error correction, and noise immunity.
These modes are all sent and received using audio frequencies that fall in the normal voice range used in amateur radio, about 300-3000 Hz. Some modes use very little bandwith, as low as 31Hz, allowing many contacts to take place within a frequency range that would be occupied by one voice contact. These modes are most commonly used with a text interface that resembles internet chat, but are also suitable for inclusion in a higher layer of protocol which allows further error correction, block sending, and retries. When used with a ‘stack’ like this, it is possible to send binary files over amateur radio error-free. This is useful for emergency communications. An example is to be able to send a spreadsheet listing items needed at a shelter, instead of reading and copying every line in the document by voice. The low speeds of these modes limit the usefulness to relatively small files, but a lot of information can be passed in small text files.
Fldigi runs on Linux, Free BSD, Windows XP, W2K, Vista, and OS X. At the hamfest, Dave will be demonstrating using windows and a Linux platform, and I will be helping him demo with my Ubuntu system.
The forum is at the Huntsville Hamfest from 14:00-16:00 on Saturday August 15th, in Salon 10. For more information about these apps, see Dave’s site
We’re very lucky in Madison County and in the entire state of Alabama to have a capable group of radio amateurs who are involved with the emergency and disaster response planning at both state and county levels. We train and work with these agencies, and have a good working relationship with those agencies. Post-Katrina, radio amateurs from Alabama provided valuable service for months in the disaster areas.
Recently, there was a full scale statewide interoperability test. Here’s a good article about it. This test was designed in part to test integration of amateur radio operations with the state’s extensive communications capabilities.
My participation was limited to checking my station, making sure my generator would start, and checking in as available for service. That doesn’t sound like much but when you consider that hundreds of other people across the state are doing the same thing, you can see how quickly communications can be established after a disaster, even if everything is down. Everything. Power, telephones, cell phones, and internet.
