(Updated 7-12-05 to show CTCSS tones required)

Central Indiana
Skywarn Radio Network

Radio Systems Used In Network & Tower Site Providers

This page is to help explain the radio network used by Central Indiana Skywarn during net operation.  How the network is connected and all the frequencies used during net operation.

The main repeater in the Skywarn radio network is the 146.970 Mhz (77.0 Hz Tone Required during net operation) system located in Indianapolis.  The controller in this repeater provides for all the control of connecting all of the system together used in the radio network.  This repeater is linked to the 442.650 Mhz (77.0 Hz Tone Required during net operation) repeater located at a different site in Indy to allow for coverage on both 2 meters and the 440 band from central Indiana.  Each repeater provides slightly different coverage areas do to their locations, antenna height & antenna mounting location on the towers.

After both of the repeaters are connected in Indianapolis the network is then connected to the 147.435 Mhz Simplex (77.0 Hz Tone Required) remote link package located in Freetown, Indiana in Jackson Co. in southeast Indiana.   This package helps to provide better coverage from the southern counties in the Skywarn Warning Areas.

Now to insure better coverage for the Skywarn net operation the 444.350 Mhz repeater in Terra Haute, Indiana (operated by Illiana Skywarn group) is connected into the network.  With the addition of this repeater into the network, coverage from the western counties in Indiana and beyond into Illinois for net operation is made much easier.

Next the 443.775 Mhz (88.5 Hz Tone Required during net operation) repeater in Lafayette, Indiana is added into the network to also improve the coverage of the Skywarn Network into the northwestern counties in the coverage area.  This system will also provide coverage beyond Tippecanoe and Warren counties into northwest Indiana.

So when the National Weather Service Forecast Office at Indianapolis request Skywarn Net activation for severe weather, all of the above frequencies are available to communicate from your county back to NWS.  So make sure to take the time to check-out which frequency works best from your location during the monthly test net that are held on the first Monday of every month at 8:00pm local time so you will be prepared when the real thing is needed.  You can also check the map at the bottom of the page that might help in showing which frequency would provide best coverage from your location.

System Notes:

The transmitted CTCSS tone on 146.970 Mhz is changed during Skywarn net operation ONLY to 77.0 Hz from it's normal operating tone of 107.2 Hz.  This tone is transmitted only during incoming signals to the repeaters receiver so no reset tones or ID's will be heard if your radio in set-up to decode this tone.  So if you want to go to bed at night and not be bothered by hearing the normal communications but want to know if a weather net is activated, make sure to set your radio up to decode this tone frequency and you will only hear communications if the net is activated !

The same thing would work for anyone utilizing the Freetown simplex link frequency.  By monitoring the 147.435 Mhz and setting your radio to decode the 77.0 Hz tone you would not hear any simplex traffic that might take place on this frequency until the net is activated also !

This Does Not happen on the 442.650, 444.350, or 443.775 repeaters !

The following map is provided to show the horizon coverage area for each of the current systems used in the Skywarn Radio Network.  These coverage area contours for each system can very greatly depending on your personal radio set-up.  The contours are based on each systems antenna elevation over the surrounding area.

(Click On Map To Enlarge)
Provided by: W9HRI