Copyright 1997, 1998, 1999 Virginia ARES/ RACES, Inc.
Nonprofit reproduction is permitted with source attribution
C.Edward Harris, KE4SKY, AEC Fairfax ARES
If amateurs take repeater systems for granted and depend on them, ARES and RACES are less able to respond during an emergency. If one or more repeaters go off the air from icing or power failures, the remaining ones become overloaded. It is difficult to coordinate regional activities if everyone tries to use the same few repeaters!
Realistic disaster training anticipates that some or all local repeaters may be unavailable.
In the aftermath of a severe storm, repeaters may be on battery power, which must be conserved, so we shouldn't expect them to "always be there" to compensate for weak individual stations. Local and regional response plans must stipulate when simplex is appropriate, including guidance to manage communications if one or more repeaters go "down."
Repeaters should be used for "talk-in" and to reach into areas with poor simplex coverage, but don't encourage their use as your primary working frequency. If a local event covers a radius of only a few miles, use simplex instead of tying up a machine. Keep the repeater available for priority traffic, by using it mostly as a backup or when wide-area coverage is specifically needed.
Operators need to know their assigned simplex frequencies to use for local nets, coordinated with nearby jurisdictions, which follow approved band plans and channelization! Virginia District Two issues a laminated wallet card with a contact list of emergency telephone numbers and a regional frequency list. This encourages operators to pre-program and routinely use regional T-MARC coordinated simplex channels for each city or county in our ARES District.
New operator classes should stress operating skills, "good amateur practice," safety, preparation and proper use of equipment, beyond the minimum needed to "pass the test." Encourage new hams to participate in public service events and nets to learn essential skills, such as handling NTS traffic, so they will gain experience and confidence enabling them to become skilled, effective emergency communicators.
Stress in nets, club events and exercises the appropriate use of simplex while teaching directed net procedures. Show the why, how and when to change from repeater to simplex operation. If a repeater is "down," nets should meet on the repeater output simplex. Instruct operators to listen routinely to a repeater's input frequency. If both stations have good copy, change to simplex and free up the machine. Pause 2-3 seconds between transmissions, leaving breaks for stations with priority traffic, or needing fills or relays.
Teach new operators the routine use relays to operate in a simplex environment.
On simplex it is important to open the squelch to listen for weak stations, instead of keeping it tight to reduce noise. Encourage use simplex on weekly training nets as a reliability check of your emergency equipment, instead of using commercial power. New operators also need to be taught to use plain language, correct "pro words" and ITU phonetics on phone and how to program a new frequency, offset and CTCSS tone not already in memory.
Hand held transceivers are not adequate as primary rigs for emergency communications!
If an HT signal is so weak that it cannot be copied, it takes double the air time and battery consumption from others to provide relays, repeats or fills. Having "only an HT" limits users to nearby repeaters or simplex within a few miles.
Stress the use of minimum power needed for reliable communication, but remember that with simplex, the emphasis must be on RELIABLE. New operators should be encouraged to buy 50w mobiles as first rigs, because they cost little more than an HT, but have far superior simplex performance. Guidance is necessary on appropriate power levels for working simplex versus local or distant repeaters.
If a repeater goes off the air, operators need adequate power to continue on simplex, including listening for and relaying weak stations! Use adequate output power to get the traffic through the first time, but don't waste limited battery capacity by inefficient use of excessive power, causing interference to distant stations you cannot hear, violating standards of good amateur operating practice!
Transportable VHF operators for county-wide nets need 25 watts output and at least a 3db gain antenna elevated 15 ft. or more above ground elevation. Hand held users need external battery power to maintain 5w into a higher-gain directional antenna, such as a 3 or 4-element yagi, or to augment their HT with a 25-30w brick amplifier into an elevated omni-directional antenna, such as a J-pole. Fixed stations need equivalent anntenna height and gain, and adequate auxiliary power to last a minimum of 24 hours.
ARES operators need to know how to call up and run a net. In an emergency your "regular" net control may be busy elsewhere! Occasionally for your weekly nets, don't schedule a net control. Use the opportunity for what we call a "wall flower drill."
The script for our Virginia District Two ARES Net is available upon request for any who want to adapt it to start a similar training net in their local area. Contact [email protected]
Most directed nets follow a similar procedure.
NCS comes up on the working frequency and asks if it is in use. If the frequency is clear, call the net, then state its purpose and that it is directed. Ask if there is any emergency or priority traffic. If there is, then deal with it immediately! Call for liaisons from other nets, served agencies or stations with traffic and ask for any relays.
Emergency nets don't take check-ins to build a roster, but to match up needs with assets. NCS asks who has traffic or information, determines which stations can handle the traffic or task, assigns stations to handle it, deals with it as it comes and moves on. If the net is not busy, traffic may be passed on the net right then and there.
When traffic is heavy, NCS should direct stations off frequency to pass their traffic while the net proceeds. Stations sent off-frequency should check back into the net when finished. Moving an entire net in unison to an alternate repeater or simplex should be done only as a last resort, because some stations are likely to get lost in the shuffle.
A "weak signal" rig is recommended for the primary NCS because its improved sensitivity brings in fringe stations that a typical FM mobile can't even hear. All-mode transceivers which don't receive outside the 2-meter band are also much less susceptible to intermodulation distortion from other nearby paging and commercial transmitters. ARES must be able to operate in high RF environments in close proximity to emergency services, hospital paging and other users. Use of CTCSS encode and decode helps to reduce interference, but when the squelch is open mixing products may still get in. In our experience notch filters are better for IMD suppression in typical ARES application than helical cavity bandpass filters. This is because they are compatible with dual-band rigs, are less expensive and often more effective when a strong near-field source desenses a typical wide-band mobile transceiver, which most operators have.
Fairfax ARES conducted tests at Fair Oaks Hospital within 20 ft. of a paging transmitter in a rooftop environment with multiple commercial and public safety users. These proved to our satisfaction that a Par Electronics notch filter was more effective than a DCI-146-4H helical cavity bandpass. Without the filter, a dual-band mobile transceiver was so heavily desensed that local DC Metro Area repeaters which were normally full quieting were barely readable.
Based on our tests INOVA Fair Oaks Hospital purchased a VHFDN152-158 filter for ARES. This eliminated almost all paging noise whereas the DCI "can" did not. While noticeable desense was still there when the pager was active, reliable repeater contacts were possible throughout the DC Metro area and into West Virginia up to 80 miles away. On 2-meter simplex contact was reliable to hospitals 15 miles away, impossible with the DCI bandpass when used in the same environment. Low-loss UHF pass-through enabled UHF contact between hospitals within Fairfax County.
Dual-band rigs are desirable, because UHF is more effective than VHF in built-up urban areas. We sometimes use cross-band repeat to conduct nets from within shelters or hospitals and to reach into low areas with poor simplex coverage. The 220 MHz band is quiet, less affected by intermod than 2 meters, gets out of buildings well and has good simplex propogation. If you have enough operators with 220 capability, you should use it also.
The importance of increasing antenna height cannot be stressed highly enough. A 4-element yagi elevated 15 ft. with 25w from an HT+brick amp out performs 100 watts into a typical mobile whip mounted on the car trunk lid. If you don't use a portable mast, at least drive to a high spot away from power lines to operate.
Using a portable mast mounted base antenna or yagi enables you to use less power to save your batteries. Some of our operators use a ground radial adapter which enables a mobile antenna to be attached with hose clamps and elevated on a portable mast. The rest use a small dual-band base antenna with at least 3db gain.
Cushcraft's AR-270 dual-bander is only 3.75 feet high, 5/8 wave on 2m and collinear on 440. It fits into a car trunk when assembled. Its performance and VSWR are also acceptable on 220 and it's ideal for portable use or attic installation where there are restrictions on outside antennas. While most mobile VHF operators use 5/8 wave 2-meter whips (which also work as a 1/4 wave on 6 meters) serious 2-meter mobile simplex operators like the Diamond SG7900 or Hustler CG144 collinears.
Bicycle / motorcycle / marine mobiles, fiberglass van or ambulance bodies without a metal ground plane require either dual-band mobile antennas which are half-wave on VHF (Diamond SG7200 or Comet CX-224) or half-wave mono-banders which provide unity gain without a ground.
For fringe operation , small yagis such as Cushcraft's A148-3S or 124WB are compact, have good gain and a wide useable pattern. Shorter yagis (5 elements or less) can be used in fixed position without frequent re-aiming required of long "boomers." Color-code elements, use wing nuts to ease reassembly and store in a capped PVC pipe.
It is basic to emergency operation that stations have battery or other auxiliary power sufficient to operate for at least 24 hours. One amp-hour per watt of RF output power in battery capacity should be considered the minimum.
"Barefoot" HT operators need at least a pair of 12-volt, 2ah gel cell batteries, extra NiCd pack, AA battery case, plus a gain antenna such as a telescoping half-wave, "tiger tail" counterpoise, a mobile mag mount or wind-up J-pole.
Powering a mobile rig from the car battery works OK for only a few hours. It is wasteful of scarce gasoline in a real emergency to run the engine for 10 minutes out of every hour to keep the battery charged, when there may not be electricity to run the pumps!
A better technical solution is to equip a vehicle with dual batteries and an isolator diode obtained from a boating or RV supplier so that both batteries are charged by the vehicle alternator, but isolated when discharging. If the vehicle is not driven regularly, connect solar panels equal to 1-1/2 to 2% of the battery capacity to maintain the battery banks against self discharge when the vehicle is idle. Solar panels are self-regulating if their current doesn't exceed 2% of battery capacity. No charge controller is then needed.
A lower-cost option is to carry a boxed deep cycle battery and fully-automatic, low amperage AC charger such as the Schumacher Electric Mod. SE-1-12S (from Wal-Mart, $25).
Carry basic emergency equipment in your car to include essential tools; first aid kit; some emergency cash (enough for a tank of gas, hot meal, and a room); coax and antenna; battery, power cords and wall charger; a ABC fire extinguisher; three days supply of nonperishable food and drinking water; sanitation supplies and medications; rain gear, sturdy shoes and a change of warm clothing.
Despite their poularity, gel cells are not "the answer" for ARES because they are not deep cycle and depth of discharge over 25% significantly reduces their life! They are unuseable below -20oC, in the engine compartments of vehicles or other uses subjecting them to temperatures above 50 degs. C.
Gel cells must never be charged at over 14 volts or with unregulated current exceeding 1/10 of their capacity. Gel cells larger than 10 amp/hours can be left continually on a fully-automatic, low amperage charger without harm, but should never be allowed to "float" endlessly without automatic shut-off.
For portable operations requiring movement in support of SAR or wildfire suppression, a 15-18ah gel battery such as those used in fire alarm panels and emergency lighting will fit in a brief case or backpack and power a 5w HT, laptop, GPS and TNC all day.
Better for extended "portable ops" is a BCI Group U1 33ah AGM battery, as used in wheel chairs. These weigh 25 pounds, fit in a .50 cal. steel ammunition and run a 25w mobile or laptop, TNC and separate voice and data HTs all day. Two U1's power a dual-band mobile on 10w cross-band repeat for 48 hours. For continuous operation alternate between two batteries, recharging in 8-hour rotations. If unable to recharge batteries, the primary net control needs at least a BCI Group 27 (95 ah) battery to go around the clock.
But they must be boxed, stored upright and lose half of their capacity below freezing. Delco-Voyager or GNB-Stowaway sealed-flooded, deep-cycle/RV batteries with recombinant caps give acceptable service at low cost. In Group 27 size they are $59 with a trade-in at Wal-Mart or K-Mart. Better for severe service, high vibration, extreme temperature environments are valve regulated AGM batteries used in military or public safety vehicles and by the US Coast Guard. A Group 27 Concorde Life-Line (65 lbs., $189) has aircraft-type cell construction and is UPS shippable from West Marine, (1-800-BOATING). It can power a 100w HF rig all day. Lifeline batteries come in the small U1 size as well as the popular Group 24, 27 and 30 marine sizes and for commercial applications up to 255 ah.
The usual failure mode of dry NiCds used in hand held transceivers is not "memory" effect , but either deep discharge causing cell reversal or diminished capacity caused by excessive charge current or prolonged slow over charging. The general rule for charging dry NiCds is to increase the rated voltage by 15% to overcome internal resistance and charge at a current equal to 10% of the battery capacity, times ten hours.
We do not recommend for ARES the use of mag mounts constructed using RG-58 coax having a solid center conductor. This cable is suitable only for permanent vehicle installations where it will not be subjected to repeated flexing. Factory installed crimp-type UHF connectors on mag mounts should be cut off, replaced with solder type and reinforced behind the reducer with heat shrink or tape. Frequent flexing eventually causes failure of the shield at the connector, at the worst possible time.
The best simplex performance results from the most efficient antenna, at the greatest height above ground elevation with the shortest run of low loss feed line, providing the highest effective radiated power for the least battery consumption. A unity gain, quarter wave mag mount thrown on top of the nearest metal object may work fine for local repeaters, but on simplex will be lacking, unless you have height and a "straight shot." We recommend use RG8-X for HF runs less than 100 ft., jumpers and VHF up to 40 feet. Use RG-8 or RG-213 for 6 meters and below for runs up to 200 ft. and 9913F on two meters for runs over 40 feet and all uses above 200 MHZ.
By training to operate effectively on simplex, ARES is more flexible and able to maintain emergency communications, even when the repeaters go down.
Page Last Updated, 05/09/09