FishFAR Radio Group

WA9VGI/R

Serving Chicago since 1974

News & Information

FISHFAR REPEATER NETWORK NEW USER INFORMATION

            The Fishfar repeater network is an amateur radio system consisting of multiple receivers and transmitters designed to cover the Northeast Illinois area. It has multiple transmitters because one transmitter cannot reach the entire desired area. It has many more receivers than transmitters to allow for the use of portable radios, and to help to fill in dead spots.


REASONS FOR MULTIPLE RECEIVE SITES

            Because a portable radio only puts out a few watts, and our transmitters put out hundreds of watts, your portable radio can hear our transmitters from much further away than our transmitter site can hear your portable’ few watts. We put receive sites in strategic areas outside a transmitters portable coverage range. An example of this would be as follows: You can hear our transmitter with your portable from 40 miles away, but you cannot get in with your potable until you are 15 miles or less from the transmitter (because of the difference in power between our transmitter and your portable). We would put a satellite receive site about 25 miles away from the transmitter, so when you are 35 miles from the transmitter, the satellite receive site will hear your portable, and allow you to use the repeater. We call them satellite receivers, not because they have anything to do with a satellite in the sky, but because they are removed from the main site.


MANY RECEIVE SITES AT THE SAME TIME

            There is another reason for having many receive sites, and that is to try to make sure you have as good of a signal as is possible. Here is how that is accomplished. All of the receive sites are connected to a unit called a voter (actually there are many voters) that listen to the receivers, and digitally decide which one has the best signal quality, and then put that receive site on the air. When you transmit you will usually be heard by multiple receivers. The voter is continuously listening and comparing your signal from every receiver your transmitter is getting into, and picking the best sounding receiver site to put on the air. If you were to drive into an area where you became noisy into the presently selected receive site, the voter will figure out what other site you sound the best in, and switch the transmitters audio to that receive site. During the time of one transmission, you could stay voted into one receiver the entire time, or switch between sites may times if you have a marginal sounding signal into the receivers, as the voter keeps trying to pick the best one.

 
MDC ACCESS

            The repeater uses MDC to identify and allow only valid users repeater access. MDC is a Motorola name for a specific type of data burst. The data burst consists of a specific hexadecimal code. Most Motorola radios, and some other brands, are capable of generating “MDC 1200” which is the specific type of MDC used by the repeater. There are also circuit boards that can be installed in radios that can generate the data burst. The data burst is sent out as soon as you depress the push to talk button, and the repeater will let your signal pass thru if you are a paid member with a valid MDC code. You will be given your mdc codes and setup information when you pay your dues.


FREQUENCIES

            The repeater transmits on UHF frequencies of 442.900, 442.925, 442.950 and 442.975 with a PL of 114.8 (2A). It also transmits on the VHF frequency of 146.925 with PL 100.0 (1Z).
            You will normally transmit on normal repeater offsets of these frequencies, plus 5 Mhz for UHF and minus 600Khz for VHF. You will usually transmit on the corresponding input of the transmitter you can hear the best. Your audio will come out on all transmitters simultaneously.