Tutorial NOAA Weather Radio SAME

Tutorial: NOAA Weather Radio (SAME)

What it is. NOAA Weather Radio is the US and Canadian service that broadcasts weather forecasts and alerts around the clock on seven narrow-FM channels between 162.400 and 162.550 MHz. Each alert starts with a short data burst, SAME (Specific Area Message Encoding), which carries the event, the affected areas and the time. OnAir decodes the burst and presents the alert as readable text, with a history and a state-level map. The mode is receive only and is not an alerting system: do not rely on it for your safety.

What you need

• Radio. Any radio that tunes 162 MHz. The mode asks for 2 Msps; the lowest rate that works is 1 Msps; the channel width is 25 kHz. An RTL-SDR is enough. See Supported-radios.
• Antenna. A VHF antenna, vertical; a transmitter site is usually within 40 to 60 km of the listener. A small telescopic whip often works; an outdoor antenna improves range.
• Frequencies. The seven channels 162.400, 162.425, 162.450, 162.475, 162.500, 162.525 and 162.550 MHz (WX1 to WX7); the default is 162.550 MHz. These exist in the US and Canada. Elsewhere you will hear nothing.

Before you start

• Tune to the channel your local transmitter uses (the Channel setting lists the seven channels); the other channels are other transmitters.
• Gain: moderate. Keep clear of the DC spike (set a small offset).
• SAME bursts are short (a few seconds) and sent three times, so keep the receiver running to catch them.

Step by step

1. Mode list, group Weather & science, entry Weather alerts, 162.55 MHz.
2. In the Receiver tab choose the Channel (WX1 to WX7) and the Country (US or Canada). The US and Canadian codes overlap (35 is New Mexico or Ontario), so the Country setting is yours to choose.
3. Press Start.
4. Open Alerts, Map and Raw.
5. Optional: County CSV, Load a county table so counties have names. Nothing is downloaded and no county names are built in (see below).

What you should see

You hear the voice forecast; when an alert is issued, a row appears in Alerts with the time, event and areas. The status line shows how many of the three repeats agreed. A weekly test (required weekly test) appears at a regular time.

Reading the screen

• Alerts. Columns UTC, Event, From (originator), Areas, Valid (how long it is valid), Repeats. Selecting an alert shows Message, Code, Part, Area, as sent. Events use the full plain-English EAS names; a code not in the table is shown by its code and its warning / watch / statement kind. copy puts text on the clipboard.
• Area codes. Partial-county direction: whole county, northwest, north, northeast, west, central, east, southwest, south, southeast. State and province names are built in; counties show as "county FIPS 113, Texas" until you load a county CSV.
• Map. A state-level map with the area markers (approximate: it marks the middle of the state or province, moved slightly toward the partial-county direction). fit zooms.
• Raw. The raw messages as received, each with copy all.
• Attention tones. The 1050 Hz tone that follows the header, with its length; "none heard" appears when no tone was detected.

Options and settings

• Channel, Country, County CSV (Load / Unload). Accepted lines: SSCCC,Name, SS,CCC,Name or the Census file national_county.txt. The path is remembered.
• Test signal: a tornado warning for three locations with partial county codes, the tone and the ends, then a required weekly test.

Troubleshooting

• Nothing decoded. Is a transmitter in range? Check for the voice broadcast first.
• Damaged message. A message that fails is listed as damaged with the reason; if the repeats disagree, the bit-voting rescues it.
• Wrong state. The Country setting; US and Canada share codes.
• Counties are numbers. Load a county CSV.
• Hiss and drift. Check frequency offset; a modest offset is tolerated.

Tips

The weekly test is a good check that everything works. Keep the receiver on a dedicated old PC if you want a log.

Legal and privacy notes

The text of an alert is a public broadcast. Receiving is legal. OnAir is not a warning system. See Legal.

Under the hood

AFSK at 520.83 baud, mark 2083.3 Hz and space 1562.5 Hz, bytes least significant bit first after 16 bytes of 0xAB. The header ZCZC-ORG-EEE-PSSCCC...+TTTT-JJJHHMM-LLLLLLLL- is sent three times, then NNNN three times. The three repeats are voted bit by bit and every field checked (47 CFR 11.31 event table; FIPS PUB 5-2 location codes).

Related

Mode-NOAA-Weather-Radio-SAME, Tutorial-FM-radio-with-RDS, Legal, Troubleshooting