UHF-Satcom.com - L-band reception

Don't forget - if you want to chat about L-Band reception, pop along to the #hearsat IRC channel, details here

L-Band downlinks mostly consist of traffic which is delivered to mobile users - there are exceptions to this of course. At L-band you can hear Inmarsat digital telephony / data, Weather Fax, Iridium telephony, and many streams of telemetry type traffic. There is about a 50/50 split in the traffic as to its origin, with some coming from Geostationary satellites, other traffic from orbiting satellites. One particularly interesting set of LEO L-Band satellites are those that form the COSPAS-SARSAT search and rescue satellite radiolocation system, a separate page dedicated to this is here. Work has been progressing on an Inmarsat pager obtained from eBay, you can read about that here.

In order to successfully receive L-band signals, you will need a good preamplifier - the 13cm/23cm VK5EME preamp is recommended for this as it provides a low noise figure and high associated gain. Coupled with the preamp, a suitable antenna must also be used. For feeding either an offset or prime focus dish, a 3.5 turn helical can be used (details below). Few L-band downlinks are linearly polarised, the exception is Meteosat at 0W which uses horizontal polarisation. The frequency range to define L-band as far as satellite downlinks go, can be from 1.3GHz to 1.7GHz. Recently, these preamp boards have become available from "Monitoring Monthly", a UK radio magazine, details here - these LNA's are perfect for Inmarsat.

The picture to the top left shows an assembled VK5EME dual stage LNA board. N sockets are used as they are low-loss at 1.5GHz. This particular LNA is suitable for Inmarsat Reception due to its low noise and high associated gain.

The custom milled enclosure was chosen mainly for mechanical rigidity reasons.

Bottom left shows a new version of the LNA which is boxes and ready to go as a plug and play solution to L-Band reception. The LNA has been checked for any self oscillations caused by being mounted in the box, and none were found. In fact the performance has been excellent.

If you are in the UK or Europe you can buy one from Monitoring Monthly. Please mention UHF-Satcom.com as the place that you saw the LNA mentioned. Incidentally, the DC power is fed up the coax from the matching DC-Power inserter.

A simple LHCP helical antenna centred on 1550MHz is described to the right - this antenna can be used with prime focus or offset dishes. This antenna is ideal for Inmarsat reception when combined with a 60cm to 90cm dish and suitable LNA board such as the one mentioned above.

The dimensions are not overly critical, but should be within a couple of mm of those quoted. The ground plane can be made from PCB or aluminium, and its recommended that an SMA or N-Type connector is used. The helix element can be made of 1.5mm or 2mm wire - the prototype used 2mm silver plated copper wire. The helix element can be made self supporting, but its better practice to make a supporting rod from nylon or plastic. The first quarter turn of the helical should be bent to be parallel with the ground plane, leave a 1mm gap here.

L-Band sky survey - contributions from #hearsat (xBr, PJM, Kodar, Gonzo, hfid, BLH, Freq, `r00t) - Antenna used were generally dishes. Work is progressing well on the Inmarsat B-Gan system which allows IP LAN extensions over satellite - this is using an eBay sourced B-Gan modem which has been placed in promiscuous mode. In addition to B-Gan, Std-B, Mini-M, Std-C and Std-D+ are work in progress. Std-C is based on a thrane & thrane TT3022C terminal, with demodulator data tapped out and parsed with custom PC software, details to follow. The Inmarsat Std-D+ terminal was acquired via eBay and work has progressed very well in reserve engineering the firmware, details here.

Position Freq Modulation 98W 1534.455 LES 054 - TDMA BPSK 1200bps Joint NCS+TDM (local = 3) Inmarsat 2F2 1534.790 LES 251 - TDMA BPSK 1200bps Joint NCS+TDM (local = 2) (Freq, blh) 1534.810 LES 253 - TDMA BPSK 1200bps Joint NCS+TDM (local = 2) 1534.830 LES 254 - TDMA BPSK 1200bps Joint NCS+TDM (local = 2) 1534.880 LES 252 - TDMA BPSK 1200bps Joint NCS+TDM (local = 2) 1535.175 Veripos DGPS correction data 2438Bd BPSK (High Power) 1537.750 Inmarsat TDM channel 1200bd DBPSK (xBr recording) 1538.379 multiple tones (similar to mfsk, but slower.) 1539.779 multiple tones (same as 1538.3790, but weaker.) 1540.025 Analogue voice channel 1540.050 Analogue voice channel 1540.075 Analogue voice channel 1540.925 Inmarsat TDM channel 1200bd DBPSK (xBr recording) 1540.950 Analogue voice channel 1540.975 Analogue voice channel 1543.140 LES 052 - TDMA BPSK 1200bps Joint NCS+TDM (local = 0) 1543.160 LES 053 - TDMA BPSK 1200bps Joint NCS+TDM (local = 0) 1543.180 LES 054 - TDMA BPSK 1200bps Joint NCS+TDM (local = 0) 1543.205 LES 051 - TDMA BPSK 1200bps Joint NCS+TDM (local = 0) 1543.230 LES 051 - TDMA BPSK 1200bps Joint NCS+TDM (local = 1) 1543.290 LES 051 - TDMA BPSK 1200bps CES TDM (local = 2) 1543.305 LES 053 - TDMA BPSK 1200bps Joint NCS+TDM (local = 1) 1543.345 LES 053 - TDMA BPSK 1200bps CES TDM (local = 2) 1543.355 LES 052 - TDMA BPSK 1200bps Joint NCS+TDM (local = 1) 1543.380 LES 052 - TDMA BPSK 1200bps CES TDM (local = 2) 1543.395 LES 054 - TDMA BPSK 1200bps CES TDM (local = 1) 1543.4075 digital + tone (high baud rate) 60W 1676.000 Digital data GOES-10 1681.475 Digital data (09/03/2008) 1692.700 Carrier 1694.000 Digital data 1694.300 Carrier 53W 1531.140 6Kbps BPSK Inmarsat-B/M Inmarsat 4F2 1532.700 Wideband PSK 160KHz BGAN (26/01/2008) 1535.035 MFSK slow rate data 40bd Inmarsat-D 1535.045 MFSK slow rate data 20bd Inmarsat-D 1535.055 MFSK slow rate data 20bd Inmarsat-D 1535.115 Veripos DGPS correction data 2438Bd BPSK 1537.550 6Kbps BPSK Inmarsat-B/M 1537.560 6Kbps BPSK Inmarsat-B/M 1537.600 6Kbps BPSK Inmarsat-B/M 1537.700 NCS 044 - Network Coordination Station TDMA BPSK 1200bps 1537.860 MFSK slow rate data 20bd Inmarsat-D 1537.880 MFSK slow rate data 20bd Inmarsat-D 1537.890 MFSK slow rate data 20bd Inmarsat-D 1537.900 MFSK slow rate data 20bd Inmarsat-D 1537.970 Pulsed PSK modem 1538.010 6Kbps BPSK Inmarsat-B/M 1538.020 6Kbps BPSK Inmarsat-B/M 1538.030 6Kbps BPSK Inmarsat-B/M 1538.040 6Kbps BPSK Inmarsat-B/M 1538.060 6Kbps BPSK Inmarsat-B/M 1538.120 6Kbps BPSK Inmarsat-B/M NCS 1538.380 ID 002 - MFSK slow rate data 20bd Inmarsat-D Bulletin Board 1539.525 LES 021 - France Telecom MSC TDMA BPSK 1200bps 1539.535 LES 001 - Southbury USA TDMA BPSK 1200bps 1539.555 LES 002 - Stratos Burum Netherlands TDMA BPSK 1200bps 1539.565 LES 004 - EIK Telenor Norway TDMA BPSK 1200bps 1539.585 LES 012 - Stratos Burum Netherlands TDMA BPSK 1200bps 1539.685 LES 003 - KDDI Yamaguchi Japan TDMA BPSK 1200bps 1539.750 MFSK slow rate data 20bd Inmarsat-D 1539.7575 ID 012 - MFSK slow rate data 40bd Inmarsat-D 1539.760 MFSK slow rate data 20bd Inmarsat-D 1539.7675 MFSK slow rate data 20bd Inmarsat-D 1539.770 MFSK slow rate data 20bd Inmarsat-D 1539.7775 MFSK slow rate data 20bd Inmarsat-D 1539.7825 MFSK slow rate data 20bd Inmarsat-D 1539.785 MFSK slow rate data 20bd Inmarsat-D 1539.7875 MFSK slow rate data 20bd Inmarsat-D 1539.790 MFSK slow rate data 20bd Inmarsat-D 1541.280 6Kbps BPSK Inmarsat-B/M NCS 1542.500 Wideband PSK 160KHz BGAN 1545.900 Wideband PSK 160KHz BGAN 1546.0475 Framed PSK 1546.062 Framed PSK 1536.0925 Framed PSK 1546.610 Wideband PSK 40KHz 33.5W 1540.870 TT&C sidebands at +- 4KHz Marisat-F2 (09/03/2008) 15.5W 1526.280 6Kbps BPSK Inmarsat-B/M Inmarsat 3F2 1528.290 6Kbps BPSK Inmarsat-B/M (30/12/07) 1528.300 6Kbps BPSK Inmarsat-B/M 1532.490 6Kbps BPSK Inmarsat-B/M 1535.105 Veripos DGPS correction data 2438Bd BPSK 1536.250 256bps BPSK 1 second framing (perhaps for Russian Volna system) 1537.120 6Kbps BPSK Inmarsat-B/M 1537.1395 6Kbps BPSK Inmarsat-B/M 1537.150 6Kbps BPSK Inmarsat-B/M 1537.160 6Kbps BPSK Inmarsat-B/M 1537.170 6Kbps BPSK Inmarsat-B/M 1537.190 6Kbps BPSK Inmarsat-B/M 1537.200 6Kbps BPSK Inmarsat-B/M 1537.210 6Kbps BPSK Inmarsat-B/M 1537.220 6Kbps BPSK Inmarsat-B/M 1537.320 6Kbps BPSK Inmarsat-B/M NCS 1537.550 6Kbps BPSK Inmarsat-B/M 1537.600 6Kbps BPSK Inmarsat-B/M 1537.680 6Kbps BPSK Inmarsat-B/M 1537.710 LES 103 - KDDI Yamaguchi Japan TDMA BPSK 1200bps 1537.750 Inmarsat TDM channel 1200bd DBPSK (xBr recording QRT 31/12/07) 1537.870 ID 102 - MFSK slow rate data 20bd Inmarsat-D Bulletin Board 1538.220 6Kbps BPSK Inmarsat-B/M NCS 1539.505 LES 112 - Station 12 Holland TDMA BPSK 1200bps 1539.515 LES 116 - Psary Polish Telecom TDMA BPSK 1200bps 1539.595 LES 104 - EIK Telenor Norway TDMA BPSK 1200bps 1539.615 LES 102 - Stratos Burum Netherlands TDMA BPSK 1200bps 1539.625 LES 114 - Tangua Embratel Brazil TDMA BPSK 1200bps 1539.635 LES 117 - Nudol Morsviasputnik Russia TDMA BPSK 1200bps 1539.645 LES 120 - Thermopylae Greece TDMA BPSK 1200bps 1539.655 LES 112 - Station 12 Holland TDMA BPSK 1200bps (not always tx'ing) 1539.695 LES 105 - Fucino Telecom Italia TDMA BPSK 1200bps 1539.7625 MFSK slow rate data 20bd Inmarsat-D - QRT? 1539.7725 MFSK slow rate data 20bd Inmarsat-D - QRT? 1539.955 LES 101 - Southbury USA TDMA BPSK 1200bps 1539.965 LES 122 - Stratos Global Australia TDMA BPSK 1200bps (Tnx `r00t) (on demand) 1539.985 LES 127 - Emeq-Haela Bezeq Israel TDMA BPSK 1200bps (Tnx `r00t) (on demand) 1539.985 LES 116 - Psary Polish Telecom TDMA BPSK 1200bps (on demand) 1539.995 LES 121 - France Telekom MSC TDMA BPSK 1200bps (pjm recording) 1541.000 Continuous carrier 1541.0175 MFSK slow rate data 20bd Inmarsat-D 1541.0275 MFSK slow rate data 20bd Inmarsat-D 1541.0475 ID 103 - MFSK slow rate data 40bd Inmarsat-D? 1541.1275 ID 103 - MFSK slow rate data 40bd Inmarsat-D (same tfc as 1541.0475) 1541.450 LES 144 - NCS 1544.500 SAREX downlink 1545.015 600bd FSK 1545.030 600bd FSK 1545.040 600bd FSK 1545.055 Framed FSK 1545.070 Framed FSK 1545.085 Framed FSK 1545.100 Inmarsat data (xBr recording) 1545.195 600db FSK 1548.500 1000bps BPSK 1575.420 EGNOS overlay This C to L Transponder RX band MHz TX band MHz cross-strap Forward 6424.000 to 6454.000 1525.000 to 1559.000 info applies to Return 1626.500 to 1660.500 3600.000 to 3629.000 all Inmarsat C to C 6432.300 to 6433.200 3607.300 to 3608.200 satellites. L to L 1640.850 to 1641.850 1539.350 to 1540.350 Nav (Egnos etc) 3629.400 to 3631.600 1574.400 to 1576.600 0W 1686.830 WB data - approx 750KHz wide (has 8X carriers each side) Meteosat 1691.000 Meteosat APT / WEFAX QRT 14/06/06 1693.830 Carrier 1694.500 Meteosat HRPT 1695.665 Chopped carrier 1695.720 PSK Data 1695.755 Data (GMSK?) 1695.785 Data (GMSK?) 21E 1469.000 DVB Mux Afristar 1471.000 DVB Mux 1473.000 DVB Mux 1475.000 DVB Mux 1488.000 DVB Mux 1490.000 DVB Mux 1491.699 Afristar TT&C 24.5E 1528.250 QPSK 3380Bd 804bit frame (Tnx to `r00t for updates) Inmarsat 1528.310 QPSK 3380Bd 804bit frame 3F5 1532.910 QPSK 3375Bd 804bit frame (probably not 1533.660 BPSK 6000Bd a production 1533.670 BPSK 6000Bd Inmarsat sat) 1533.680 BPSK 6000Bd 1533.690 BPSK 6000Bd 1535.080 Veripos DGPS correction data 2438Bd BPSK (High Power) 1535.1525 Veripos DGPS correction data 2438Bd BPSK (High Power) 1535.165 Veripos DGPS correction data 2438Bd BPSK (High Power) 1536.201 BPSK 3840Bd DSSS Drifting -86Hz/10min, recync after 7mins 1537.6375 BPSK 6000Bd 1545.540 BPSK 1200Bd 106.7ms ~ 128bit 1548.360 PM Data, data subcarriers 500Hz & 4500Hz 1548.525 BPSK 1125Bd 56.9ms ~ 68bit (changed to fast 4800Bd? BPSK for a while) 1551.600 Wideband PSK 1551.755 Wideband PSK 1551.940 Wideband PSK 1552.090 Wideband PSK 1575.420 Egnos overlay data (xBr recording) 64E 1535.070 Veripos DGPS correction data 2438Bd BPSK Inmarsat 1535.115 Veripos DGPS correction data 2438Bd BPSK 3F1 & 4F1 1537.100 NCS TDMA BPSK 1200bps 1537.340 NCS Mini-M 1537.995 ID 302 - MFSK slow rate data 20bd Inmarsat-D Bulletin Board 1538.180 NCS (Inmarsat B / M) 1539.355 LES 330 - Vishipel Viewnam TDMA BPSK 1200bps 1539.365 LES 303 - KDDI Yamaguchi TDMA BPSK 1200bps 1539.385 LES 335 - Fucino Telecom Italia TDMA BPSK 1200bps 1539.395 LES xxx - Haiphong TDMA BPSK 1200bps 1539.405 LES 316 - Psary Polish Telecom TDMA BPSK 1200bps 1539.415 LES 312 - Stratos Global Australia TDMA BPSK 1200bps (local = 0) 1539.425 LES 301 - Southbury USA TDMA BPSK 1200bps 1539.435 LES 305 - Thermopylae Greece TDMA BPSK 1200bps 1539.455 LES 304 - EIK Telenor Norway TDMA BPSK 1200bps 1539.465 LES 328 - Sentosa Singapore TDMA BPSK 1200bps 1539.485 LES 302 - Stratos Burum Netherlands TDMA BPSK 1200bps 1539.495 LES 311 - Beijing MCN China TDMA BPSK 1200bps 1539.705 LES 312 - Stratos Global Australia TDMA BPSK 1200bps (local = 1) 1539.772 MFSK slow rate data 20bd Inmarsat-D 1539.777 MFSK slow rate data 20bd Inmarsat-D 1539.945 LES 341 - 1539.975 LES 317 - Nudol Morsviasputnik Russia TDMA BPSK 1200bps 1540.948 MFSK slow rate data 20bd Inmarsat-D 1540.958 MFSK slow rate data 20bd Inmarsat-D 1540.968 MFSK slow rate data 20bd Inmarsat-D (reserved channel) 1540.978 MFSK slow rate data 20bd Inmarsat-D (reserved channel) 109E 1535.175 Veripos DGPS correction data 2438Bd BPSK (High Power) Inmarsat 2F4 178E 1535.105 Veripos DGPS correction data 2438Bd BPSK Inmarsat 3F3 Galileo LEO 1176.450 DSSS 23MHz b/w See chart below 1196.910 DSSS 23MHz b/w 1202.025 DSSS 23MHz b/w 1269.031 DSSS 18MHz b/w 1271.077 DSSS 20MHz b/w 1276.192 DSSS 23MHz b/w 1278.750 DSSS 23MHz b/w 1281.307 DSSS 23MHz b/w 1286.422 DSSS 23MHz b/w 1288.468 DSSS 23MHz b/w 1561.186 DSSS 4MHz b/w 1564.050 DSSS 4MHz b/w 1565.190 DSSS 4MHz b/w 1569.486 DSSS 4MHz b/w 1573.987 DSSS 4MHz b/w 1576.852 DSSS 4MHz b/w 1581.353 DSSS 4MHz b/w 1585.650 DSSS 4MHz b/w 1586.789 DSSS 4MHz b/w 1589.653 DSSS 4MHz b/w

Metop-A 1701.300 HRPT 3.5Mbps QPSK 1544.500 SARSAT transponder Iridium LEO 1616-1626.5 Iridium Phone to Satellite (Thanks to IW for this info) Simplex Channel 1616-1626.5 Satellite to Iridium Phone/Pager 1 1626.020833 Guard Channel 2 1626.062500 Guard Channel 3 1626.104167 Quaternary Messaging 4 1626.145833 Tertiary Messaging 5 1626.187500 Guard Channel 6 1626.229167 Guard Channel 7 1626.270833 Ring Alert 8 1626.312500 Guard Channel 9 1626.354167 Guard Channel 10 1626.395833 Secondary Messaging 11 1626.437500 Primary Messaging 12 1626.479167 Guard Channel Duplex Channels Lower Edge Upper Edge 1 1616.000000 1616.333333 2 1616.333333 1616.666667 3 1616.666667 1617.000000 4 1617.000000 1617.333333 5 1617.333333 1617.666667 6 1617.666667 1618.000000 7 1618.000000 1618.333333 8 1618.333333 1618.666667 9 1618.666667 1619.000000 10 1619.000000 1619.333333 11 1619.333333 1619.666667 12 1619.666667 1620.000000 3 1620.000000 1620.333333 14 1620.333333 1620.666667 15 1620.666667 1621.000000 16 1621.000000 1621.333333 17 1621.333333 1621.666667 18 1621.666667 1622.000000 19 1622.000000 1622.333333 20 1622.333333 1622.666667 21 1622.666667 1623.000000 22 1623.000000 1623.333333 23 1623.333333 1623.666667 24 1623.666667 1624.000000 25 1624.000000 1624.333333 26 1624.333333 1624.666667 27 1624.666667 1625.000000 28 1625.000000 1625.333333 29 1625.333333 1625.666667 30 1625.666667 1626.000000 GLONASS Constellation L1 1598.0625 & 1607.0625 (1603.700 xBr recording) L2 1242.9375 & 1249.9375 L3/L5 1198.546875 & 1205.296875 GPS MEO Constellation L1 1575.420 (xBr recording) L2 1277.600

AFSTAR POD - Inmarsat C transceive antenna - ideal for use in an L-band receive system.

The picture below shows the PCB layout. On the left hand side, the power amplifier can clearly be seen. The PA consists of 5 microwave transistors; The part numbers, going in a counter-clockwise direction are : 2 X 2SC2340, MRA1600-2, MRA1600-13 and the final is an MRA564. This is also the path that the transmit RF takes, although it's passed through a gain block first, after the input duplexer. On the right hand side, the receive section is shown. The receive path is: Front end antenna duplexer followed by a 2 stage low noise gasfet preamp, followed by a helical filter centred on 1553.25 with a bandwidth of 46Mhz. This filter is then followed by a gain block (8 pin sm IC) and another filter centred on 1553.25 with a bandwidth of 46Mhz. Finally, another gain block, and then into the output duplexer which feeds the N connector coax feed. There is a DC tap from the N connector, and this supplies voltage to the PSU circuits.

The reason for the additional ground on pin D is as follows: Blue water ships often use isolated grounding to help prevent electrolytic actions taking place. In an amateur environment, it is possible to connect pins A and D together. (Thanks to JDN for this info) Pins B,C and D are all opto isolated.

The pictures below shows the omni-directional antenna that's used in the pod antenna. As far as can be told, it seems to be a set of phased 1/2 wave antenna's. There is a phasing harness between the two aluminium discs, and this outputs to the duplexer input on the above PCB. The antenna is not suitable for feeding a dish, as it's omni-directional and right hand circular. The antenna works very well attached directly to a GPS, although if its to be used for wider coverage at L-Band, then the internal filters will need removing and replacing with semi rigid links.

1694.500 digital weather data dissemination	Meteosat 0w data
Iridium satellite downlinks at 1616-1626.5 MHz	AOR-W Inmarsat MFSK channels (cf=1539.765MHz)
COSPAR-SARSAT downlink on 1544.500MHz	GLONASS downlink on 1603.700MHz
L3 Military GPS receiver board for guided missiles	Anti-jam GPS antenna cluster from Raytheon
21E Afristar 1491.699MHz TT&C

A	Ground
B	TX/RX Control (+VDC Transmit)
C	Power control (+VDC = High power)
D	Control Return (Ground - can be connected to A)
E	Transmit Indicator (output)
F	HPA over temperature indicator (output)

(above) Modified antenna suitable for feeding a dish.	(above) Original onmi-directional antenna
(above) Omni antenna removed for GPS use.