In our previous article we had started to review some situations in which the use of free and open source software (FOSS) could be useful in obtaining and managing information. Now we see how to make that information reach the citizens.
A few years ago, radio stations in the United States asked the regulator to be mandatory the inclusion of an FM receiver in each smartphone. Although most analysts suspected that it was a way to reduce the market loss at the hands of Sptify and iTunes, the excuse was that the radio was the best system for delivering emergency alerts.
The providers and terminal factories assured that they had a unified system of alerts, and in fact, they did the test last year when the cell towers transmitted for half an hour, the following test message in English and Spanish
«Presidential Alert
THIS IS A TEST OF THE NATIONAL WIRELESS EMERGENCY ALERT SYSTEM. No action is needed.
Personally, I am in favor of the inclusion of an FM receiver. On June 16 of last year, a series of wrong decisions left the entire Argentine Republic without electricity for several hours. Those who had not taken the precaution of charging their mobile devices (and did not keep radios and battery-powered flashlights) had a pretty bad time. Keep in mind that the battery consumption of the radio in the mobile is lower than that of the other functions.
Free software for crisis. Amateur and professional stations
Unless things get very out of control, it is not possible that the current pandemic will leave us without television, cable and internet. However, communication by means of radio waves continues to be essential for other types of emergencies. We can distinguish two types of stations. amateurs and professionals.
We must clarify that amateur station He is not a person playing radio in his garage. It is an internationally regulated activity by a United Nations body called International Telecommunications Union. Radio amateurs they must obtain a license that demonstrates their technical knowledge, and operate within strict rules.
Local and international amateur radio networks They have proven their effectiveness by keeping communications open when other mechanisms failed.
Open source hardware and software for radio amateurs
Single board computers like the Raspberry Pi, due to their small size, low price and low consumption, they are ideal for the activity. some possible uses are:
- Decoding of digital radio signals: By connecting a compatible audio card and installing a software called FLDigi, it is possible to receive and decode signals RTTY (radio teletype) PSK (phase shift modulation) and CW (continuous wave) among others.
- Remote reception: Radio waves can travel a limited distance. It is possible to configure the Raspberry Pi together with additional hardware and software called SDR # to receive the signals and relay them via the web.
- WSPR transmitter: The WSPR protocol consists of the transmission by software of low frequency signals. Since this includes the geographic location of the transmitter, it can be decisive for the location of people injured or trapped in a disaster.
- Access point: To different data transmission networks via radio waves.
- Position tracking and transmission system using APRS: APRS stands for Automatic Packet Reporting System. Using it, it is possible to see on a map the location from which a fixed or mobile amateur radio station operates. It also makes it possible to access meteorological information, signaling on the map of all other types of events of interest.
Even though we didn't specifically mention it, All of these activities require the installation of additional modules. However, there are radio amateurs who sell the Raspberry Pi together with the modules and the necessary software.
I tried to take every precaution so that my translation of the technical terms was as accurate as possible, but, it may be that I have made mistakes. If there are any radio amateurs in the audience, the comment form is available for corrections.
Very good note, I bring you some comments and clarifications as a radio amateur that I am (LU7GAB license).
As for the blackout in Argentina on 16/06/2019 (Father's Day), early, communicating (by radio) locally on the VHF band with a couple of colleagues, I could see from the very low noise level on HF that something was not he was doing well, that situation was not normal. I quickly gathered some items and went to our radio club (LU4GF, http://www.qsl.net/lu4gf/) assuming that the thing was important and a communication center was needed for which our radio club is always available. Indeed, it was a national blackout and a favorable consequence for radio communications is that the level of atmospheric noise normally produced by today's electronic equipment, in particular switching power supplies and LED lights, drops a lot. I have a couple of videos that I made at that time in case you want proof. Luckily in our area there were no emergencies to attend to.
One piece of advice for readers is to find out where there is a nearest radio club or radio fan, they can search the internet or simply see where there are "rare antennas" (vertical antennas, with long wires and Yagi type).
On the other hand, as a GNU / Linux user I have a Raspberry in my workshop and as part of my radio field activities.
Here I want to make a clarification regarding "Radio waves can travel a limited distance." mentioned in the note, this depends on which band is used and we radio amateurs know that well: for short distances we mostly use the VHF band, for longer distances to cover the world we use HF.
Speaking of SDR there are WebSDR sites (which require internet), SDR is a technology (Software Defined Radio) and there are many programs that use that (there is not ONE program called SDR). There are also many programs for "digital modes" in addition to the aforementioned FLdigi.
I must also emphasize that amateur radio only needs "a transceiver equipment, a battery or generator and an antenna to communicate" (in case of blackouts), also with a pc / notebook / raspberry we can transmit data and images.
I hope my comments are useful, anything I am available for clarification, even as a GNU Linux user (I always read your articles :))
Thank you very much for your interesting comments.
In one of the sources I consulted for the article a software called SDR # (SDR SHARP) is mentioned and this is what I put. Here is the download link
https://airspy.com/download/