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Radio Technical Information

Radio broadcast is one method used by the NWS and other public and private agencies for disseminating the EMWIN datastream.  To receive an EMWIN radio broadcast, hardware and software are needed.

If you are within 40-50 miles of an EMWIN radio transmitter, all you need is an inexpensive radio receiver, a decent antenna, a demodulator, and a personal computer. EMWIN software on your PC, running under Windows, receives the signal from your radio through a serial port, stores the received weather products onto disk, and simultaneously allows you to display this information.

EMWIN VHF Reception Notes

What Do I Need?

  1. a location within 40-50 miles of the transmitter in one of the Broadcast Areas.
  2. A modern PC with Windows
  3. EMWIN receive/display software,
  4. A demodulator (see example below) which can be bought assembled (see vendors).
  5. A radio receiver or scanner tunable to the broadcast VHF or UHF frequency.
  6. A decent antenna, depending upon range, line-of-sight, and shielding.

How Do I Load the Software?

For commercial vendor software, see their instructions.

How Do I Hookup the Hardware?

Connect the audio output of your receiver to your demodulator input; connect the demodulator RS-232 output to your COM port.

How Do I Get It Working?

You will initially need to experiment with placement and orientation of your antenna. Remember: you can listen to the audio modulation on your radio corresponding to each block of data, which are sent every 10-15 seconds, at 1200 baud.

Commercial Vendors of EMWIN Products

See the combined Radio and Satellite list of Commercial Vendors for radio software and hardware products, including the basic demodulator.

EMWIN Schematics

Various transmitter/receiver "baud rates" have been utilized for EMWIN, from the original basic 1200 baud up to 9600 baud (i.e. after demodulation into RS-232 data). The following are examples of circuits for transmitting and/or receiving at various speeds.

Xenocode DM-201B Demodulator Schematic (1200 baud)

This is one example, courtesy of Xenocode, Inc., of a demodulator to receive the basic EMWIN audio signal and convert to 1200 baud RS-232 serial ASCII data. There are many similar public-domain demodulator circuit designs using various ICs, such as the XR-2211 chip or TCM3105JL chip to demodulate plus a MAX-232ACPE chip or equivalent to convert to RS-232.

The current EMWIN Radio broadcasts are receivable, when demodulated, as async 1200,8,N,1.

Xenocode DM-224A Demodulator Schematic (2400 baud)

This example, courtesy of Xenocode, Inc., of a demodulator to receive an EMWIN 2400 baud audio signal and convert to 2400 baud RS-232 serial ASCII data. 

ZE DM-96 Demodulator Schematic (9600 baud)

This is one example, courtesy of Zephyrus Electronics, Ltd. (with additional text by Xenocode, Inc.), of a demodulator to receive an EMWIN 9600 baud FM scanner signal and convert to 9600 baud RS-232 serial ASCII data.


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