R303-137 Weather Fax Receiver Board

Direct reception of the 137 MHz weather satellites is a fascinating hobby for many and a necessity for others who are dependent on the weather.

The R303-137 is a very sensitive wideband fm receiver optimized for reception of NOAA APT and similar weather facsimile images on the 137 MHz band. You can use it with any popular APT software. The R303-137 is based on our popular R303 ham band receiver. It was designed as a lower cost alternative to the R139 Receiver.

The R303-137 has excellent sensitivity (0.2µV); so no preamp is needed for normal operation. Special wideband filters enable low distortion for high quality imaging, even with doppler shift on the satellite signal. The frequency synthesizer provides four channels to cover all current US APT satellites.

The R303-137 is designed from the ground up for optimum satellite reception, so it provides much better results than a modified scanner receiver.

FEATURES:

Very sensitive - 0.2 µV typical. Low-noise dual-gate FET rf amplifier and mixer.
Wide bandwidth filters for low distortion pictures; 38 kHz modulation acceptance.
Four channels - can manually select any U.S. satellite simply by soldering appropriate jumper on the pc board, or you can use an external switch (not provided). Download manual for ideas.
Frequency synthesizer for precise frequency control.
Adjustable audio output level to drive speaker and demodulator.
Separate high impedance output terminal for use with computer sound card.
Squelch indicates when satellite is heard; +5Vdc COS logic output signal available to indicate when squelch is open. (Normally not needed, but a nice feature if you are designing a special system.)
Volume and squelch controls are trim pots on board. (You can substitute external pots if you prefer.)
Complete detailed instruction manual and drawings included.

SPECIFICATIONS:

Channels supplied: 137.100, 137.500, 137.620, & 137.9125MHz NOAA APT Satellites.
Commercial grade tcxo for tight frequency accuracy in wide range of environmental conditions: 2ppm -30 to +60°C.
Sensitivity (12dB SINAD): 0.2µV
Squelch Sensitivity: 0.15µV
Normal satellite signal bandwidth: ±15 kHz deviation
Modulation Acceptance: ±18 kHz
Speaker Audio Output: 1 Watt (8 ohms).
High impedance output for computer sound card input (1Vp-p with 9kHz deviation on input signal)
Operating Power: +13.6Vdc at 38-100 mA, depending on audio level.
Size: 4 in. W x 2-1/2 in. D
Shipping Weight: 1 lb.

REFERENCE INFORMATION:

Here are some useful websites with information and programs you can download. Please let us know if you find any others we should know about or if any of these are no longer functional.

Note that we do not endorse any programs listed here as we have not tested them.

WXSat freeware program for computer imaging of APT signals from R139 Receiver.

Another freeware program which comes highly recommended for imaging.

Turnstile Antenna construction article. (See article below for photo of this antenna.)

Article by AMSAT on how to use the R139 Receiver in schools.

Review of R139 Receiver in an August 1997 QST article, which also describes freeware program for satellite imaging.

Citizen Scientist Article on R139 Weather Sat Rcvr

Background information from NOAA on weather satellites and links to related pages.

NOAA status for polar orbiting satellite websites.

PRICES:

R303-137 Receiver board wired/tested ......$229
(sorry, not available in kit form)

A2 Coil Alignment Tool .........$6.00

A40 AC adapter .......$9.50

Click here for A5 RCA plug to connect to board.

Here is a sample image made as a composite from multiple images. Click to enlarge. (Thanks to Jerry, KD6JDJ)

How to demodulate the pictures...

The R303-137 Receiver demodulates the fm signal transmitted by the weather satellite. Its 2400 Hz audio tone output must be further demodulated and converted to digital pulses, which is done with the sound card in your computer and imaging software. A special antenna provides good reception as the satellite orbits the earth.

WXSat freeware program for computer imaging of APT signals from the receiver.

LNK-137 FET PREAMP

This popular unit achieves a low noise figure (0.6 dB) with a gain of 18 dB. Operating power is +12Vdc at 10 mA, connected through a feedthrough capacitor. The 50 input and output use BNC jacks.

The preamp is connected in series between the antenna and the receiver to effectively lower the noise figure of the receiver front end, allowing weaker signals to be received. A preamp normally is not needed if your antenna feed has low loss. If you cannot use premium quality coax or if your coax is over 50 ft., this preamp installed at the antenna should improve reception.

Read all about it.

LNK-137 Preamp .......$99

(Ship wt. 1 lb.)

LNP-137 PRESELECTOR

For installations where interference is caused by nearby transmitters, such as near an airport, this low-noise preamp with a 3-section high-Q filter may solve the problem. It is installed in line with the coax from the antenna.

Maximum 40 dB rejection is obtained for signals more than 7 MHz above or below the 137 MHz band; however, some benefit is achieved even for signals closer in frequency.