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. In the first response I answered all of the questions which then resulted in a second round of questions and answers. What follows is an updated and streamlined addition of the back and forth communications…
Thank you for taking the time to respond to me. The frequency we anticipate using is a VHF channel. I have spoken with the local frequency coordinator and he has done some preliminary work to make sure that this frequency appears viable for our use. I and many of the club member have spent weeks monitoring this frequency from different locations on the ridge and it appears unused with the closest repeater being over 100 miles away and shielded by mountains from our location. We cannot activate either repeater from our area. I have monitored over 70 repeater pairs to come up with this one. It is not easy given our reach over the valley.
The repeater equipment is a bit of a mystery to me. We have many members with legacy, nondigital 2 meter equipment. Our primary goal is to have solid communication equipment that everyone can use and would be usable without an internet connection in an emergency. Secondarily we would like to have digital capability to link with other repeaters and networks. The club enjoys experimenting and like the idea of being able to communicate with distant places utilizing digital connections. I’m not all that impressed with digital only systems for voice only. I appreciate the ability to use my own ears to distinguish weak signals and don’t appreciate the sudden fall off of digital however I am not the only voice in the club. I need some specific help with the pros and cons of specific equipment. For instance I know the Yaesu makes a repeater that will service both digital and analog communication in a mixed mode platform. Is there other digital/analog repeaters that use DMR that will do mixed modes? Is D-Star capable of doing mixed modes or a better question might be are there repeaters that will do D-Star and analog in a mixed mode fashion? Is there specific equipment we should look for or avoid?
Commercial antennas make sense to me. I am all about reliability. I would like to see an antenna stay in place for a long time. I have no desire to hire someone to climb a tower to fix or replace antenna that is not robust or has inadequate gain characteristics. Again if you have specific recommendations or antennas we should avoid I would love to hear it.
Unfortunately I know we will be making some compromises due to budgetary concerns but I want to see us make good informed decisions and move forward in a methodical reasoned approach. Thank you for your words of wisdom. Your insight is invaluable.
Finding a clear channel on VHF is an accomplishment and a great first step.
Now for the rest of your questions.
D-Star vs DMR. Go with DMR since there are several commercial manufacturers building equipment to support DMR and NBFM. D-Star is an older technology and has poor audio response…it is on its way out. Yaesu, Kenwood, Motorola has DMR equipment and there are other manufactures as well. BUT…see the next paragraph…
Another comment about dual mode repeaters, DON’T DO IT! The repeater is more expensive to purchase and will add to the confusion during a real emergency. Pick NBFM (Analog FM) since 99.9% of the hams have it. You can’t get a sanction for a DMR repeater on a analog channel which is VHF…maybe someday but not now.
Digital Connections during an emergency? DON’T DO IT! If you want to overload your communications system, link during an emergency. Public Safety agencies have learned that you have an operational channel and other channels available for backup. During an emergency you will use VHF in your immediate area. You don’t need or want someone from an area outside of your operational area “trying to help” via a linked channel. Your operational channel is for the incident in your area and only the your area. An example: Many years ago there was a pipeline explosion in Walnut Creek. Walnut Creek PD had this wonderful linking system in place and decided to use it. They linked the Contra Costa Sheriff’s Department, Lafayette PD, San Ramon PD together on their main operational channel. One dispatcher can handle 10-20 units at a time maximum…not 100 units all trying to help. It was a communications disaster. This is just one lesson learned from years of working in the Public Safety communications field…
Linking is something to play with during non-emergencies. you can use EchoLink or IRLP to link via the Internet or establish a RF link using another ham band like UHF. Linking gives you a larger footprint for radio coverage when you don’t have a lot of users. It is useful to your repeater user who still want to talk to their friends back home while traveling outside of your immediate coverage area.
The CCRA has 3 linked repeaters that cover the SF Bay area and Sacramento, San Joaquin area. We discourage rag chewing and ask users to keep conversations down to 10-15 minutes. We don’t permit one rag chewer to monopolize the repeater all day. This “guidance” is to instill some level of discipline to how the repeater is used day to day so that when we do have an emergency users already know how the repeater(s) will be used during an emergency. For example, we have multiple nets during the week so people get used to how a repeater is used during an emergency. In addition, during an emergency we can break the links between the repeaters so local traffic stays local. Due to their high level locations it can still serve areas outside of the immediate operational areas but so far, that hasn’t become an operational problem.
If you want keyboard to keyboard digital communications then use packet radio. It can be built for communications between emergency locations to track people, equipment and other resources. Again work with your local governmental agencies and groups like the Red Cross, Salvation Army, etc…
In my prior email I alluded to the importance of good commercial equipment to be purchased. Hams have gotten a bad reputation for taking the inexpensive way out. In the past hams wanted to put antennas all over the tower with little thought to how it will trash the proper operations of a radio site. When a radio site owner sees you have made the investment into the proper equipment you will have a better chance they will open the door for you to use their site. If you are using less than commercial equipment they will not be interested in having you occupy their site since you pose a very real possibility for causing their existing users interference.
I hope this keeps you pointed in the right direction.