How to Build a Repeater???

Recently I received an email from a fellow ham asking for guidance to build a repeater in an area devastated by a natural (unnatural) disaster.

As background, my fellow ham provided a history of what had happened, what their group wanted to do and their need to build a repeater for use during future emergencies. After thinking about the questions that were raised, I wrote this brief response.

Thank for the overview of where you are and where you want to go.  I believe your approach is sound.  Building a repeater system needs to be approached in the same way you eat an elephant…one bite at a time.

My first question to you is what frequency(s) or bands do you intend to put your repeater on…UHF, VHF, low band (6 meters) or something else?  Depending on the repeater pair, the NARCC coordinator can determine your chance of getting or giving interference to an existing repeater that share your frequency.  This is something that will directly affect how well your repeater will work and play with other repeaters on the band.  Due to your elevation, there is a high probability you could get and cause interference from other repeaters a hundred miles away. It is good that you are working with the NARCC coordinator and he should be able to help you in the frequency selection.

The second step is to select a site that provides the radio coverage your group needs.  So site location is critical.  There is software that can model repeater coverage based on location (lat/long/elevation), area terrain, frequency, antenna type and pattern, etc.  This will give you the best indicator on radio coverage to expect.  The NARCC coordinator should be able to help you with this…if not, I might be able to help you with this. 

You want to select a radio site that is a real radio site.  If you intend to work with governmental agencies during an emergency you need to establish a relationship with an agency before the emergency.  The Sheriff’s Office, Police or Fire Chief, City or County government official is where I’d start.  They should have radio sites that are built to withstand natural disasters.  If that is not the case then they are really in trouble.  I’d work with the agency to put the repeater at their site.  They should have an emergency generator, commercial power, towers and security which should keep vandalism to a minimum.

You stated you would like to have an analog/digital repeater.  Commercial equipment is available with this capability.  Use the KISS (Keep It Simple Stupid) Method.  In reviewing how other hams have approached this emission question I find they either go with analog or digital since having both emission types in the same repeater can cause user related problems which is the last thing you need during an emergency.  Another concern is how a digital repeater coexists with an analog repeater located miles away and sharing the same frequency.  Personally I prefer analog since you can tell when a user is getting into a marginal coverage area.  With digital, you go off the digital cliff and you are gone.  This is especially true in mountainous areas.  If you want digital for tracking users or sending traffic it might be best to approach this with a separate packet system with its controller located in a different location from the voice repeater.  A separate digital system would provide a redundant communications path in an emergency.

Another suggestion is to build your radio system right the first time.  I’ve seen too many hairball installations where people cut corners and ended up making the radio system unusable.  If you are going to put up a system you can depend on in an emergency, you need to make it as bullet proof as possible in the beginning.  This also goes for site selection.  A well built repeater system will require little maintenance in the long run.  Buy a commercial repeater, use a duplexer if you are the only one on the radio site.  If you share the site with other transmitters it might be better with a split antenna system with separate TX/RX filtering systems.  Use lightning protection such as a Polyphaser and a well built commercial antenna that cost approximately $1K-2K.  Putting an antenna in a tree is my definition of hairball…

If you want to continue the conversation, I’m available…

73...Steve, WA6HAM