ARRL Certification Program
Emergency Communications
Net Operations

That is why it's so critical to learn and master these skills in a less demanding and "mistake-friendly" environment.  If you don't, the time you'll learn this is when it's for real.
 

Net operations for emergency communication is really about being able to receive, handle and direct traffic to the appropriate net.  Each net has a different communications protocol in response to it's intended mission and to make effecient use of the net time.  For example, the calling net will use tactical, rather than formal traffic handling.  For this reason, one should gain experience both operating and being net control for these various types of nets.
1. Command Net
• This is usually the first net up upon activiation.  It takes check-ins from those activated, coordinates the initial response, and provides a means for keeping responders updated on activities.  For this reason, it is usually tactical in nature, under net control.  Stations may be calling each other on this channel, then move off onto another frequency to develop the conversation. Those in command will eventually make more use of the net and as operations members establish operating nets, that traffic will move off the command net in accordance with ICS protocol.
2. Calling Channel/Calling Net
• As the situation expands, calling may move to a dedicated repeater or frequency serving the affected area.  Since there is so much chaos happening at each site, stations that are not directly participating in the emergency may have to assist by monitoring the calling activity, get in touch with the site by QSYing to the primary frequency that the site is monitoring and contact that site to inform him that someone is calling on the calling channel.
3. Operations/Message Passing Net
• Long messages such as formal traffic should be passed on it's own frequency or repeater.  A formal piece of traffic will block tactical messages and calls, so it's best to isolate formal traffic to it's own frequency/repeater.
• Stations passing traffic should allow time for the operator at the other site to handle unannounced distractions and should wait a few moments for contact to resume.
4. Logistics Net
Similar to the command net, the logistics net arranges for personnel, equipment and other materials.  Much of the traffic is tactical and informal.  Occassionally, a piece of formal traffic involving logistics materializes.  It should be passed on it's own net or frequency, away from the logistics net..
5. Bulletins
Special stations (not the NCS station) originate and pass along bulletin messages generated by an appropriate party.  Shorter bulletins may be passed on a tactical net frequency.  Longer bulletins should be passed on another frequency to avoid blocking a tactical net.  NCS stations should announce that a bulletin station will originate the bulletin, give the amount of minutes before the start of the bulletin, and the frequency of the bulletin traffic.

1. Standard Operating Procedures

For a standard operating procedure to be used for all nets, for all agencies, see:
http://home1.gte.net/rhashiro/am-ec-sop.htm
The stuff below is standard to any traffic net.
2. Checking into the net
3. Handling station logs
4. Relaying for other stations
5. Going to a backup frequency
6. Temporarily leaving the net
7. Being relieved by another station
8. Initiating formal traffic
9. Checking out of the net

• Simplex and line of sight
• Simplex nets are best used long haul between two points, or in a geographically limited area -- such as responding to a high-rise building fire.  It is also an operating practice and insurance against loss of net discipline when a repeater fails due to power or equipment problems.  Operators should be trained and expect to flip from repeater to simplex operations when a repeater is suspected to be down.  The alternate simplex frequency for each district should be predetermined ahead of time.
• An efficient operation messaging net would have the NCS station on a calling frequency, and the NCS would direct the two parties to reestablish contact on another channel.  The protocol is that the person sending the message is the one that calls the receiving station.
• Keep in mind that on a simplex net, stations at the physically opposite ends of the net will probably not hear each other if the radius of the net area is too large.  If the NCS is in the middle, you may have to relay.  If the NCS is not in the middle, other stations may have to relay.
• An advantage of simplex nets is that low powered walkies on a tactical, operational frequency do not have to reach a distant repeater to get a solid signal to relay back to nearby stations -- you simply go direct.  If you use fairly low power (1/2 watt), you can populate the area with many walkies without saturating and desensing radios that might not be the case if you had to use high power (5 watts) to reach a local repeater.  And, you conserve battery power.
• Before building a simplex operation into your emergency communications response plan, organize a simplex radio test for a given Saturday morning.  This will help you collect data on radio propagation that will enable you to know ahead of time the strengths and weaknesses of simplex operation in that district.  For a test procedure, see:

http://home1.gte.net/rhashiro/am-ec-simplex-test-procedures.htm
• Repeaters
• Because of its uniform and consistent coverage within a given service area, repeaters should be used primarily for tactical messages, command and logistical nets.  Formal message handling is best handled on simplex, HF NVIS or a high orbiting OSCAR satellite such as Phase 3D.
• SSB vs FM
• On SSB, make an effort to zero beat with the Net Control Station.  The NCS's frequency is the net frequency.
• If the signal starts to fade on FM, see if you can establish a SSB net on another frequency.  SSB requires about 10 dB less signal than FM to accomplish the same connectivity (per Zack Lau, formerly KH6CP).  -10 dB is equivalent to a 100 times decrease in power.
• NVIS antenna and how it helps
• NVIS is an HF antenna for operation between 5 to 10 MHz.  It is kept low to the ground (horizontal, between 3-10 feet) to use the earth as a reflector and send the signal to the ionosphere.  The ionosphere refracts the signal back to earth, in a service radius of about 250 miles.
• Propagation varies during the time of the day, so an NVIS antenna is usually broadbanded to allow the operator to switch bands as necessary.  Therefore, amateur NVIS net operations show up on the 40m and 80m bands.
• As NCS, you should be equipped and prepared to operate on 40m and 80m.  Siimilarly, if you're a net operator, be equipped with 40m and 80m antennas and tuners.
• Some signals area easy to hear, and some signals will be more difficult.  Keep in mind to ask for a relay as needed to keep the net flowing.
• AutoPatch/Phone Patch
• During operations, it's convenient to have and use a phone patch to allow people in the field to converse with non-amateurs directly.
• If you don't have a hybrid phone patch, you can fake one using a phone handset moved up towards the speaker of the radio.  You'll need to listen in the handset earpiece for comments by the party on the phone, and relay that to the radio.  When you do, speak into the radio microphone and the phone handset microphone at the same time, so both parties can hear the transmission.
• Data Links
• If you can establish private data links between major EOCs, do so.  It is often faster to send a message digitally, than to have the sender read it, and the receiver copy it manually.  One should keep the amount of stations on the frequency to a bare minimum (2), so there are no collisions or interference and to keep throughput to a maximum.  Typical 1200 baud packet on a clear channel yields approximately 300 bps throughput, or about 30 characters or 5 words per second.  A collision or interference will substantially decrease that throughput.  Having more than 3 active packet stations on a channel will reduce realtime performance to unacceptable levels.

1. Desense, Intermod, frequency and space diversification

Much of the interference can be avoided by good planning.  This determines the radio bands and equipment you'll need.  This will determine the net operations.
• Recognize that in dense metropolitan environments high powered paging transmitters in the VHF and UHF spectrum will generate intermod that will cause grief.  Similar intermod can be experienced if you're next to a high powered broadcast transmitter.  (1) Use intermod filters on VHF/UHF FM equipment, (2) Use the 222 band, (3) use directional antennas, (4) use frequency diversity (HF, for example) to get away from VHF and UHF bands.
• To reduce desense to adjacent radios, run the lowest power output that maintains reliable communications.  Use long coax cables to get the antenna away from the immediate area, preferably to a nearby window or roof.  Turn down the receiver RF gain.
• If you must run multiple pieces of equipment in the same room, try some frequency or space diversity to cut down on the mutual interference each radio equipment will contribute to surrounding radios.
2. Living wth interference
• Use and leverage various filters, (1) at the antenna port, (2) plug into the radio in the IF sections, (3) DSP for IF and audio, (4) notch, IF shift and passband filters, (5) headphones and boom mikes.
• Switch to CW, and narrow the filter bandwidth.
• If you're NCS, move the net frequency to avoid the spot with the interference.