Updated March 2021

Weather Satellites transmit High Resolution Pictures (HRPT) at 1.7 GHz. The transmission is not encrypted and all needed is a low noise antenna and LNA , an SDR  and suitable software for demodulation, decoding and visualization.

The minimal, portable setup regularly in use here is an Airspy Mini USB SDR ,  a 40cm diameter helicone on a tripod tracking sats by hand and a 0.2 dB NF LNA.

Details below:

SDR :

SDR Airspy Mini  and USRP1 (modified clock 48 MHz, streaming 6 MSPS)

Antenna and Tracking :

a) Hand tracking using a small low noise helicone antenna (see dimensions below)

b) Automated tracking is done using my own Satellite FUN software and a SPID BIG RAS rotator or 2x DiSEqC motors in X-Y configuration.

Relays in the Rot2Prog controller have been replaced by BTS7960 H bridges, see here.

See also my X band feed page and the dual band L/X feed setup currently in use

Low Noise Amplifier:

Modified G4DDK VLNA NF 0.2dB – absolutely important when the low noise helicone antenna is used. If such an LNA is not available I strongly recommend the use of an antenna with higher G/T . I designed the helicone just for experimentation to see e.g what is the minimum aperture that works given a 0.2 dB LNA is used.

For demodulation and decoding one could use one of the following:

a)  Aang254’s excellent free SatDump which supports VHF/ L//S/ X band weather satellites and much more :

b) Free GNU Radio scripts

c)  XHRPT software

For visualization / false color images :

a) David Taylor’s  HRPT reader  and

b) Fred Jansen’s weathersat 

Some pictures showing this small portable setup and what it can do , can be found below.

1.7 GHz helicone design:

The helicone antenna below has been simulated and optimized in CST Microwave Studio.

The goal was minimum dimensions for acceptable G/T performance.

If you decide to build this antenna, it is absolutely important to use a very low noise amplifier (0.2 -0.3 dB) like G4DDK’s excellent VLNA.

Performance will be poor with the popular Nooelec ~1.2 dB Noise Figure LNAs…Those LNA are nice especially if there is interference as they employ a band pass filter. They require antennas with higher G/T than the helicone to compensate for the higher LNA noise.