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The EMWIN data stream is intercepted from satellite by many emergency management groups, municipalities, and others and retransmitted on local and NWS owned radio frequencies. The retransmission is, in turn, intercepted by anyone within range of the signal (generally a 40-50 Mile radius from the transmitter) and displayed on their computer. Using retransmission vendor purchased software, retransmitting agencies can tailor the data to their area by eliminating products that do not apply and adding locally generated data. In addition to data from EMWIN, many retransmission sites include local road conditions, school closings, and other data that is useful to their clients.
It is now possible to rebroadcast the EMWIN bit stream intact or filtered via a set of NWS owned frequencies. These frequencies are in the VHF band and are specifically 163.300Mhz, 163.325Mhz, 163.350Mhz, 168.8125Mhz, and 168.7125Mhz.
Before applying for one of these frequencies check your broadcast area for anyone already broadcasting on one or more of these frequencies. This is not likely but could be possible. Also check for cell phone activity in your area that may be close to one of these frequencies. If the frequency is unused and there is no interference, fill out a frequency request. You can download and print both a frequency request and a cooperators agreement in PDF format for your own use to get started. The emergency manager (EM) will still need to get an official request form from the Warning Coordination Meteorologist (WCM) to get the process rolling.
In order for an EM to rebroadcast using one or more of these frequencies, he/she must first contact the local WCM and be identified as valid EM. If he or she does not know who that WCM is he or she can find out by contacting the local WFO. The WCM will then provide him or her with an official frequency request form and a cooperators agreement.
Once the frequency request is completed, the EM will return it to the WCM . The WCM will then turn it into the regional frequency manager to begin the approval process. This process involves the regional frequency manager, the NWS frequency manager, and the National Telecommunications and information Administration, (NTIA) . It takes a minimum of 15 working days. After approval, the EM can purchase the transmitter set to the assigned frequency by the vendor. Note: The type of emission is F1D and the power into the antenna feed is limited to 100 watts.
After the system is ready to operate, the cooperators agreement (operators license) is signed by both the EM and the responsible NWS official. Once signed, the system can begin transmission.
Only a transmitter that passes NTIA narrowband specifications and has passed all certification tests can be used. Also, the license requirements in the cooperators agreement must be followed.
US Dept of Commerce
National Oceanic and Atmospheric Administration
National Weather Service
1325 East-West Highway
Silver Spring, MD 20910
Page Author: EMWIN Team
Web site owner: NWS/OPS17
Freedom of Information Act (FOIA)