Emergency Communications & Repeaters in Hawaii

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.

Links to other repeater info sites:
Link Communications Inc.
Computer Automation Technology
ACC Email Discussion Group
Repeater Owners Email Discussion Group
Bat Labs
Repeater Builders Tech Info Page
GE Radio Help Page

ID O Matic $20 identifier kit

Doug Hall Electronics - Voters

GE Mastr II manual

NHRC Repeater Controllers
ACC Info Page, WA8DBW




Motorola MSF5000 UHF Repeater with CAT controller 100w

msf.JPG (72743 bytes)Plus side: Very Reliable, high power output,high duty cycle, duplexer is  internal of cabinet.This or similar would be the preferred mode of operation during or after a disaster if power is available.
Down side:greater then 100lbs  Needs 120vac or generator for emergency operations. Not be practical to operate this station from a car battery.

Typical Motorola MICOR Repeater at Haleakala 146.94 at 100w

94micor.jpg (79044 bytes)Plus side:Very Reliable, high power output, high duty cycle,Can be found on the market at reasonable pricesvhfduplexer.JPG (118843 bytes)
Down side: For VHF 600khz split minimum of 4 bottle duplexer similar to one in picture is required .VHF duplexer at 600khz split will have to be as big as the ones in the pictures above usually 8" bottles 



Another Configuration of a Motorola MICOR Repeater

This particular setup also has a General Electric MVP UHF base at the bottom of the cabinet. The CAT500DCP03849.JPG (113220 bytes) controller is in the metal box with the molex connector center shelf of card cage. If you are not familiar with the Motorola Products, seek advice from someone with experience or you may be buying one that is too far out of band and not economical to bring it into the ham band.
Plus side:Very Reliable, high power output, high duty cycle, Can be found on the market at reasonable prices
Down side:  (as above)

GE MVP UHF Mobile converted to Repeater 15 watts

mvp1.jpg (1198810 bytes)mvp4.jpg (357708 bytes)20090328treo281.jpg (206564 bytes)20090328treo284.jpg (163693 bytes) Portable UHF repeater low power 10~20w. Uses RP3A Controller 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, ID-O Matic identifier. Original suitcase form by KH7R, Retrofitted in a GR400 rack mount shelf, Samlex 20 amp power supply with forced air cooling at  back. Only Excellent quality Commercial Mobiles can be converted to a repeater because of their high selectivity qualities not found ham radio grade mobiles.
Plus side:The best for this size configuration. 
Down side:  Low power output.

Motorola Portable UHF DES Repeater 15 watts 2CIMG0017.JPG (982563 bytes)  2CIMG0010.JPG (1201426 bytes)915c_3.jpg (67566 bytes)

Motorola Portable UHF repeater modified with N bulkhead connector on back for external duplexer Celwave model 633-6A or better since I did not have an internal one, 15 watts out, uses Motorola MX HTs with transmitter feeding into the Power Amp filter strip seen in the middle picture. Capable of 120vac operation, external 12vdc or internal gel cell at reduced power.  Equipped with DES encryption or clear mode, easily transportable to incident area..


Plus side:The best for this size configuration. Excellent for on site communication coverage for special events, parades and emergency communication.
Down side: Low power output.


vhfebay.jpg (82296 bytes) vhfebay1.jpg (79748 bytes) vhfebay2.jpg (120614 bytes) vhfdescase.jpg (1418994 bytes) vhfinside.jpg (1355905 bytes) vhfant.jpg (1325734 bytes) 

$49 Motorola Portable VHF DES Repeater 25 watts

Repeater without case sold as "parts only" on Ebay . I used a tool case and cut out the front for the RF/Power panel. This Portable repeater did not have an internal duplexer as the RX /TX split was narrow being less then 5 mhz. Typically 2 meters is 600khz split and requires duplexers with a minimum of 4 each 8" cavities unlike UHF which is 5 mhz split and duplexers can be small enough to fit in the case itself. Having the RX and TX connectors already on the panel is a plus for conversion to amateur radio use with the 600khz split. I used a working VHF MX in the LO split to replace the RF modules and RX front end converting it to the 2 meter band. Sensitivity and Power out excellent, only thing left is to order crystals and change them out from the Oscillator modules. Either run split antennas or a duplexer and this is a fully functioning repeater.

VHF 130 watt 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.


digipeater.jpg (73752 bytes)AH6MG APRS DIGIPEATER on the national standard frequency standard of 144.39 Mhz. Unlike a voice repeater this repeater receives, stores and forwards the transmissions milliseconds behind the original transmissions. KPC3+ and MJF Data radio at 5 watts out.

Trackers    APRS Live tracking




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, therefore 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. Most hams only have one spare battery pack  for their HT at best and call it quits after that as they cant charge there batteries efficiently without commercial AC power. Generally, wall wart chargers are usually overnight slow chargers except for the yaesu VX5 or similar with a rapid wall wart. If you already have a fast charger that can handle 12v then you are set, if you don't, consider getting a rapid charge desk charger if you dont already have one  and use it with a 12DC to 120AC inverter similar to the one being sold at COSTCO for approximately $30.  You will then be able  to charge the batteries fast from any vehicle if the need arises. Zip Loc bag or plastic radio bag as sold by West Marine locally  is very useful if you intend to operate in rainy or adverse conditions.

Orgbox_backseat.jpg (47349 bytes)Converted "medicom" type box replaced with ham gear for quick mobile and base setup, Plug and Play. Great way to operate from a mobile command post. I use ammo cans which are cheap but if you can get ahold of something like this it would be a better package, or get a pelican case for water tight configuration.