Linked Repeater Networks
- Published: 27 January 2023
Many National Weather Service offices in the U.S. include Amateur Radio as a part of their operations plan, and most of those utilize a linked repeater network of some sort. We’re going to cover the general concept of a linked repeater network as well as how they work, and why local weather nets are often held on non-network repeaters.
A linked repeater network is a coordinated group of repeaters that rebroadcast radio transmissions picked up by other repeaters on the network, allowing ham radio operators hundreds of miles apart to communicate using a simple handheld, mobile, or fixed base radio. As a result, the NWS can keep up with weather conditions over a broad area, and operators can be forewarned of incoming weather conditions that may require local monitoring.
So, how do linked repeaters actually link? Linked repeaters have a 2nd radio interfaced with the repeater’s main radio, often called a “remote base”. This allows a signal coming in from the Remote Base to be transmitted by the repeater’s main radio and a signal coming in on the repeater’s main radio to be rebroadcast on the Remote Base. The Remote Base is programmed just like we would program our own radios to communicate with a repeater, with the repeater’s frequency, offset, and tone. To the repeater being linked to the linking repeater looks like any other radio communicating with it.
Say, for instance, that the WD4LUQ repeater on 146.895+77 in Union wanted to link to the Fayetteville repeater. The “remote base” would tune to the Fayetteville repeater’s frequency of 446.600 with a positive offset and CTCSS of 77 just like we would do on our own radios if we wanted to communicate with their repeater.
In some systems may have a Remote Base configured for just one repeater, others may have a few channels that can be switched between using DTMF, and more sophisticated Remote Bases are fully programmable remotely, allowing them to change to pre-programmed channels on the fly, or even be custom configured on the fly.
Another way to link two repeaters might be for each of the two repeaters have their own Remote Bases which would communicate over their own set of frequencies, perhaps using lesser used 220mhz frequencies.
In any case, when it comes time to bring up the linked repeater net, each repeater enables their Remote base, which now allows each of them to echo the traffic of the other. The 2nd repeater then links to yet another repeater, the process continuing until all the repeaters in the network are linked together.
Because at any given moment there may be a repeater offline, many repeater operators have backup channels programmed into their Remote Base so they can link to a different repeater and mend the broken link in the network.
These linked networks must be coordinated, otherwise a series of linked repeaters may “loop” back to one of the other repeaters already in the chain, causing the repeaters to continue to feed back into the network, causing endless transmission on the network.
So, why not link the Carrollton (W4FWD - 146.640-131.8) and other repeaters onto the NWS network? Well, for starters, it complicates coordinating the NWS network. For another, the more repeaters on the network the more “noise” from random users bringing up a repeater gets generated. Additionally, to keep the network from being congested with chit-chat, random operators calling out not knowing the linked network is up, and traffic irrelevant to the NWS being broadcast. It also limits our ability to utilize our repeater if we must minimize traffic to avoid introducing congestion on the larger linked network while dealing with a local situation.
The NWS expects only severe weather to be reported, not general weather reports. Again, this is to avoid creating congestion on the linked repeater network and leave the network clear for reporting potentially life-threatening conditions. Having said that, there are times where the NWS may request reports of current conditions in a given area, whether they are severe or not; this is usually because they see confusing or conflicting information on the Doppler RADAR.
The advantage of using our repeater for tactical traffic, off the linked repeater network, is we can share weather reports and pass non-weather related traffic when there is a lull in activity. By running a tactical net on our repeater we can communicate more freely, orchestrate our weather data collection efforts, and pass weather information that may be good to know for tactical reasons but irrelevant to the NWS.
Ideally, when running our own local weather net we would appoint a liaison to the NWS net, usually somebody with a dual VFO radio who can monitor both nets and relay relevant information from one to the other. The NWS has also been known to check in on the Carrollton repeater to directly request information.
Why Digital Communications?
- Published: 09 September 2021
We've been covering various digital modes over the past few months, particularly PSK, APRS & Winlink.
While digital voice modes like D-Star, Fusion, and others offer some other EMCOMM related enhancements to our conventional analog modes, the real improvement in our ability to communicate comes from our ability to automate various functions and communicate complex data more efficiently, digital modes that allow us to harness the power of computers.
While operators tended to deploy more as "shadows" of key personnel like ambulance drivers, police, fire, or shelter employees in decades gone by, the growing ability of local, state, and federal agencies to interoperate has virtually eliminated the need for such services.
As a result, our mission required change, and are still changing. Communities with active Community Emergency Response Teams (CERT) often embed amateur radio operators as members, serving as a CERT member, enhancing their team with additional communication capabilities. Amateur Radio operators have been included in Search and Rescue (SAR) and Damage Assessment teams during disasters as well.
Automated Packet Reporting System (APRS)
- Published: 06 May 2021
APRS is packet-based digital tracking and communication system. It's best known for allowing operators to report their position or weather station data by internet or radio and be tracked using APRS clients and websites like aprs.fi, but APRS is useful for more than that. APRS also allows simple short messages between operators, sort of a radio-based text-messaging system. As a matter of fact, there is a text-message gateway available, allowing an operator to use their APRS setup to send text messages to cell phones and receive responses!
Since APRS allows for position reporting it has applications in search and rescue, damage assessment situations, and public service events like running and bike races. By embedding amateur radio operators into the field teams their progress can be monitored via APRS utilizing both online and offline mapping systems.
Although this makes APRS a potentially robust tool for public service, it's also useful for other activities, such as our summer balloon launches, where the balloon carries an APRS transmitter we then track to recover the balloon payload, which usually includes cameras and other electronics.
- Published: 15 July 2021
Tabletop exercises are a useful tool for developing the skills to operate in a real-world situation, with the opportunity to identify many challenges and pitfalls before ever going through the effort of staging an actual exercise or deploy to an actual disaster.
Why tabletop versus a Simulated Emergency Test type exercise? Well, they are easier to plan and execute, all you need is a meeting place, and even the table is optional! Trying to coordinate an actual drill may require coordination with served agencies and place demand on physical resources like repeaters, radio equipment, or even served agency locations; all of this takes time and often places demands on other organizations.
Tabletop exercises can often be executed in an hour or two, where actual drills typically run much longer, placing more demands on the time of volunteers.
Tabletop exercises provide an opportunity to develop a plan or just work the bugs out of existing plans by playing "What if" games and talking through option when dealing with mission critical information such as knowing primary and backup repeaters, what to do when repeaters are down, frequencies and timetables for simplex communication, etc.
Introduction to Winlink
- Published: 04 March 2021
Introduction To Winlink
Winlink is an global radio based email system (and more); used by amateur radio operators, government entities, NGOs, and mariners. Each of these groups utilizes radio bands appropriate to their licenses, but despite that, they can communicate with each other and any other email user, across these different environments and conventional internet.
WInlink consists of a network of UHF/VHF and HF stations that can send, receive, and relay email messages via radio and internet. HF and VHF stations are scattered all over the world, acting as gateways to Winlink email servers, allowing radio-based Winlink stations to send and receive email over this world-wide radio network.
Programs such as Winlink Express, Airmail, and pat (for Linux) can all be used to send email via radio or directly over the internet using the internet "telnet" protocol.