Emergency Communication Fundamentals- Lessons Learned

Repeaters & Options  Basics questions and Considerations by KH7O

What kind of power available?
Power is the first requirement of operating in emergencies or under field conditions. Many have overlooked the need or availability of power in adverse conditions. Will you have commercial power available?  or generator power?  Plan this out first, no power no communications simple as that. Battery power is short lived usually not enough of it and duration will not sustain a loaded communication system after a disaster.

Location of repeater?
Just like real estate, location is everything,  The higher the better, if you dont have height such as a tall building or mountaintop you probably would not do too much good putting up a repeater of any kind and should seek alternatives such as HF SSB on 40 meters etc.

How fast do you need it on the air?
Depending on the circumstances if you need to get something up fast , a portable repeater may be the solution. Ideally a commercial repeater such as the MICOR, General Electric Master II or Motorola MSF repeater  is optimal however the above power availability and location may prevent fast movement of equipment. You will have to be the judge depending on individual purpose and use.

10 fundamentals needed for serious relief communications are the abilities for the following:

1)to sustain a significant emergency power source (not hampered by only low power capability or a hand full of batteries)

2)to sustain significant communication distance (HF or high power VHF may be required, good antenna system)

3)to sustain personal logistics in your operational area. (must be able to sustain yourself )

4)good judgement and knowledge of what type of traffic to move ,(identify/ analyze what is significant vs insignificant information , priority/non-priority, best mode if options are available)

5)prior knowledge/plan on how the local networks are structured (frequencies/identify various net controls anticipated/ primary plan/ alternate plan)

6)always plan with capability to relocate (never only from a predetermined stationary site)

7)access to gear/logistics above (will you be away from station without access to any of the above when disaster happens?)

8)create kits/ bags small scale response ( tailored kit(s) for limited response versatile)

9)reflect on your objectives (ham radio, frs, satellite radio, cell phone, or any other means of communication should be used in an emergency)

10)most important of all "hope for the best, plan for the worst" , "do as you did, get what you got"  Rick Ching KH7O


POKER (Power Outage Kit & Emergency Repeater) very tactical general use kit for traveling)

POKER.jpg (108437 bytes) 

General Electric MVP UHF Mobile converted to Repeater 20w

Portable GE MVP UHF repeater low power 10~20w. Uses RP3-A  repeater control board made for this model radio. HI-Q Front end, good selectivity excellent overall radio. Duplexer is a celwave 6 cavity reject model 633-6A.  Only UHF duplexers with 5 mhz split can be this small, samlex 20 amp switching supply, remounted into a GR400 rack frame, ID-O-Matic identifier,

 Plus side:The best for this size configuration. Offers a fairly light weight on the fly repeater
Down side:, range is limited only by actual repeater location. Low power output.

VHF Simplex Repeater using Radio Shack simplex Repeater module

simprptr.JPG (114632 bytes)Economy version portable frequency agile VHF HIGH power 130w simplex repeater offers long range in the smallest package. Good for fast response or temporary use. Built with a Mirage  amplifier being driven with a 1.5w ICOM 2AT HT, Samlex 20amp switching power supply, Radio Shack simplex repeater module compatible with (ICOM 2AT, Radio Shack ) type portables or with similar mic/ptt configurations.

Plus side long Range,  Excellent audio on repeat. Quick and cheap solution. Use it with and old Mobile or HT, can use either AC or Car Battery power . Frequency agile, no duplexer needed just dial it up. Use equipment in the shack until needed for deployment. Light weight portable, great for traveling. Equipment can be used in original configuration until needed.

Downside is:  you will hear everything you say repeated causing a conversation to take twice as long. Radio Shack repeater module no longer manufactured , typically get it from ebay. Receivers not repeater grade, you may get intermod or deaf receiver if placed in high RF areas.

VHF/UHF Base Station and Cross Band Repeater


cbrrepeater.JPG (23947 bytes)Kenwood TM733A, VHF/UHF base station and cross band repeater. Operate from your HT to a repeater at a distant location not in HT range, other applications such as using it to extend the range from within a building orTM733a.jpg (148331 bytes) shelter enabling HT access. Use in short duration activity such as parades for extended range from one end to another where there are no repeaters available. This can be packaged and transported  usually fitting inside of an old Ammo can or Pelican case for a more modern look. Radio can double as a base, or mobile, or even a mobile or fixed cross band repeater, used by a few when going into shopping malls to gain repeater access.  Keep in mind in the examples below these are just examples of what can be done on the fly to McGuiver a communication system immediately.

Plus side: frequency agile, can be used as either base/mobile or crossband repeater. light weight. You may have one already?
Down side: crossband repeat only, no inband repeat, users have to have a cross band capable radio to access, Cannot handle the continuous duty cycle. Receivers not repeater grade, you may get intermod or deaf receiver if placed in high RF areas.

Extended Long Range using 2 Cross Band Repeaters

Frequencies used are just as an example. It can be configured opposite using VHF for the point to point and UHF for the portables/mobiles to access with. With this example using 2 CBRs (Cross band Repeaters) it is possible to have an extended cbr.JPG (21888 bytes) range far more reaching then a conventional repeater.The range limitation on range is the RF range between the 2 CBR sites therefore by locating each on a mountain top or elevated location it is possible to go inter-island without much effort. In this example the HT users at each only have to be in range of their respective CBR to communicate to the HT at the distant end.  The frequencies can be reversed so that the point to point is on VHF and the HT users are on UHF, configure it to what ever meets your needs. In emergency communication operation, end users usually are using the main communications channels to pass vital traffic to a command post and not chatter between individuals therefore this is perfect for the application. Should the individual users want to hear both sides of the conversation they can punch up the VHF and UHF of the local CBR.

Plus side: frequency agile,light weight, chances are 2 hams with this type of radio similar to the Kenwood TM733A are already in your area , just needs to be packaged.

Down side: Transmissions are not repeated locally inband  therefore although you can be heard by everyone at the distant end, you will not be heard beyond the perimeter of the RF range of your HT or mobile unless users are monitoring both the VHF and UHF frequency which is not a real problem in the late model dual band HTs. Consideration should be given to the technical capabilities of the users or participants in equipment and knowledge on using their equipment in this fashion.Receivers not repeater grade, you may get intermod or deaf receiver if placed in high RF areas.

Using 2 CBRs to make a Conventional Repeater

In this example, a convention repeater is created by using 2 CBRs in the general area of each other but out of desense range, cbrrepeater.JPG (20587 bytes) there is no set distance as each manufacturer of transceivers  have different selectivity specifications for each radio as well as the power output and antenna gain/pattern will play a role. Typically a commercial radio costing thousands of dollars will have a much superior front end allowing closer proximity of the transmitting antenna then you would be able to get away with using ham radio gear.  However, by locating  2 CBRs in the general area but out of desense range of each other, it is possible to set one CBR to cross band repeat in only one direction such as 146.22 Receive and 446.5 transmit and the second CBR to Receive 446.5 and transmit on 146.82. This configuration would operate as any 2 meter repeater on the air. Frequencies are just examples.

Plus side: frequency agile,light weight, cheap., no duplexer needed
Down side: requires split locations, 2 crossband mobiles, 2 antenna setups, not continuous duty. Receivers not repeater grade, you may get intermod or deaf receiver if placed in high RF areas.

HT Tips for extended  operation 

Ham Simulated Emergency tests are done in a fraction of a day and usually with a lot of advanced notice enough for everyone to prepare by charging up batteries on HTs or fueling generators and being in the right place at the right time scheduling time off of work to participate or working around similar obstacles. In the real world none of the above will apply. Think of it this way, other then a weather emergency which you will typically get some sort of advance warning, all other emergencies / disasters occur on the fly without the courteous notification process, you must be prepared with a response plan should it be under those conditions. You may not be able to go home or to a location to get the equipment and supplies etc. 

POWER is the most important, without power you are done. 

ANTENNA  second most important, not the radio

HAND HELD RADIO specifications: