A Short Primer on Mil Sat Coms
Copyright (C) 08/2003 by Howard Fuhs
Content
Abstract
Mil Standards
Channel Lists
NATO IV Satellites
UHF Follow-On (UFO)
Milstar
Leasat
Fltsatcom Satellites
Receiving Tips
Equipment Tips
Further Readings
Abstract
This short primer on Military Satellite Communications below 500MHz is intented to give the monitoring hobbyist some insight into this specific section of the hobby and was written for the WUN Newsletter.
Especially the Military Satellite Communications below 500MHz are an easy target for the beginner to enter the wide field of satellite communications as the frequency range can be covered with simple antennas and a wide variety of low cost receivers.
Basically the Military Satellite Communication below 500MHz is thought to provide tactical communication possibilities to military units, from the single soldier up to warships, planes and ground vehicles, without the usage of large (dish)antennas and with small and easily transportable (manpack) transmitters with low power output. Furthermore it was important for the whole system design, that the antennas in use in the field must not be positioned very accurate towards the satellite, but can be pointed in the estimate direction of the satellite and still provide sufficient signal strength for communication.
Military Standards
The military satellite communication is defined in standards. The standards in question are an absolute must read for everybody interested in this sector. A lot of wrong information for the hobbyist compiled by hobbyists are available on the internet simply because nobody read the military specifications.
The standards to read are:
MILITARY STANDARD 188-181
INTEROPERABILITY STANDARD FOR DEDICATED 5-kHz and 25-kHz UHF SATELLITE COMMUNICATIONS CHANNELS
MILITARY STANDARD 188-182
INTEROPERABILITY STANDARD FOR 5-kHz UHF DAMA TERMINAL WAVEFORM
MILITARY STANDARD 188-183
INTEROPERABILITY STANDARD FOR 25-kHz UHF TDMA/DAMA TERMINAL WAVEFORM
These standards are available as PDF files on the internet. Use Google or look here.
Channel Lists
The following channel- and frequency-lists are excerpts from the original MIL-STD-188-181 document.
It may be noted that LEASAT and MARISAT are no longer in use. Nonetheless the frequency channels are part of the 188-181 standard and are published below.
MIL-STD-188-181
APPENDIX D
FREQUENCY PLANS
LEASAT receive and transmit frequencies.
Channel Plan Downlink Uplink Nominal Frequency Frequency Bandwidth (MHz) (MHz) (kHz) 1 W 250.35 SHF * 25 X 250.45 SHF * 25 Y 250.55 SHF * 25 Z 250.65 SHF * 25 2 W 263.80 297.40 500 X 260.60 294.20 500 Y 261.70 295.30 500 Z 262.30 295.90 500 3 W 251.85 292.85 25 X 251.95 292.95 25 Y 252.05 293.05 25 Z 252.15 293.15 25 4 W 253.55 294.55 25 X 253.65 294.65 25 Y 253.75 294.75 25 Z 253.85 294.85 25 5 W 255.25 296.25 25 X 255.35 296.35 25 Y 255.45 296.45 25 Z 255.55 296.55 25 6 W 256.85 297.85 25 X 256.95 297.95 25 Y 257.05 298.05 25 Z 257.15 298.15 25 7 W 258.35 299.35 25 X 258.45 299.45 25 Y 258.55 299.55 25 Z 258.65 299.65 25 8 W 265.25 306.25 25 X 265.35 306.35 25 Y 265.45 306.45 25 Z 265.55 306.55 25 9 W 243.855 316.955 5 X 243.955 317.055 5 Y 244.055 317.155 5 Z 244.155 317.255 5 10 W 243.860 316.960 5 X 243.960 317.060 5 Y 244.060 317.160 5 Z 244.160 317.260 5 11 W 243.875 316.975 5 X 243.975 317.075 5 Y 244.075 317.175 5 Z 244.175 317.275 5 12 W 243.900 317.000 5 X 244.000 317.100 5 Y 244.100 317.200 5 Z 244.200 317.300 5 13 W 243.910 317.010 5 X 244.010 317.110 5 Y 244.110 317.210 5 Z 244.210 317.310 5
* Uplink frequency is super high frequency from 7.9 to 8.4 GHz on channel 1.
MIL-STD-188-181
FLTSATCOM receive and transmit frequencies.
Channel Plan Downlink Uplink Nominal Frequency Frequency Bandwidth (MHz) (MHz) (kHz) 1 A 250.45 SHF * 25 B 250.55 SHF * 25 C 250.65 SHF * 25 2 A 251.95 292.95 25 B 252.05 293.05 25 C 252.15 293.15 25 3 A 253.65 294.65 25 B 253.75 294.75 25 C 253.85 294.85 25 4 A 255.35 296.35 25 B 255.45 296.45 25 C 255.55 296.55 25 5 A 256.95 297.95 25 B 257.05 298.05 25 C 257.15 298.15 25 6 A 258.45 299.45 25 B 258.55 299.55 25 C 258.65 299.65 25 7 A 265.35 306.35 25 B 265.45 306.45 25 C 265.55 306.55 25 8 A 266.85 307.85 25 B 266.95 307.95 25 C 267.05 308.05 25 9 A 268.25 309.25 25 B 268.35 309.35 25 C 268.45 309.45 25 10 A 269.75 310.75 25 B 269.85 310.85 25 C 269.95 310.95 25 11 A 243.945 317.045 5 B 244.045 317.145 5 C 244.145 317.245 5 12 A 243.955 317.055 5 B 244.055 317.155 5 C 244.155 317.255 5 13 A 243.960 317.060 5 B 244.060 317.160 5 C 244.160 317.260 5 14 A 243.965 317.065 5 B 244.065 317.165 5 C 244.165 317.265 5 15 A 243.970 317.070 5 B 244.070 317.170 5 C 244.170 317.270 5 16 A 243.975 317.075 5 B 244.075 317.175 5 C 244.175 317.275 5 17 A 243.980 317.080 5 B 244.080 317.180 5 C 244.180 317.280 5 18 A 243.985 317.085 5 B 244.085 317.185 5 C 244.185 317.285 5 19 A 243.990 317.090 5 B 244.090 317.190 5 C 244.190 317.290 5 20 A 243.995 317.095 5 B 244.095 317.195 5 C 244.195 317.295 5 21 A 244.000 317.100 5 B 244.100 317.200 5 C 244.200 317.300 5 22 A 244.010 317.110 5 B 244.110 317.210 5 C 244.210 317.310 5 23 A 260.600 294.200 500 B 261.700 295.300 500 C 262.300 295.900 500
* Uplink frequency is super high frequency from 7.9 to 8.4 GHz on channel 1.
MARISAT (Gapfiller) receive and transmit frequencies.
Channel Plan Frequency Frequency Bandwidth Downlink Uplink Nominal (MHz) (MHz) (kHz) A 254.150 307.750 25 B 257.550 311.150 25 C 500 1 248.850 302.450 25* 2 248.875 302.475 25* 3 248.900 302.500 25* 4 248.925 302.525 25* 5 248.950 302.550 25* 6 248.975 302.575 25* 7 249.000 302.600 25* 8 249.025 302.625 25* 9 249.050 302.650 25* 10 249.075 302.675 25* 11 249.100 302.700 25* 12 249.125 302.725 25* 13 249.150 302.750 25* 14 249.175 302.775 25* 15 249.200 302.800 25* 16 249.225 302.825 25* 17 249.250 302.850 25* 18 249.275 302.875 25* 19 249.300 302.900 25* 20 249.325 302.925 25*
* In operation, communications on the 500-kHz wideband channel (Channel C) is accomplished using frequency-division multiple access (FDMA). The channel is divided into 25-kHz subchannels with transmission data rates varying between 75 and 16000 bps.
UHF follow-on receive and transmit frequencies.
Channel Plan Downlink Uplink Nominal Frequency Frequency Bandwidth (MHz) (MHz) (kHz) 1 N 250.350 SHF * 25 O 250.450 SHF * P 250.550 SHF * Q 250.650 SHF * N' 250.400 SHF * O' 250.500 SHF * P' 250.600 SHF * Q' 250.700 SHF * 2 N 251.850 292.850 25 O 251.950 292.950 P 252.050 293.050 Q 252.150 293.150 3 N 253.550 294.550 25 O 253.650 294.650 P 253.750 294.750 Q 253.850 294.850 4 N 255.250 296.250 25 O 255.350 296.350 P 255.450 296.450 Q 255.550 296.550 5 N 256.850 297.850 25 O 256.950 297.950 P 257.050 298.050 Q 257.150 298.150 6 N 258.350 299.350 25 O 258.450 299.450 P 258.550 299.550 Q 258.650 299.650 7 N 265.250 306.250 25 O 265.350 306.350 P 265.450 306.450 Q 265.550 306.550 8 N 266.750 307.750 25 O 266.850 307.850 P 266.950 307.950 Q 267.050 308.050 9 N 268.150 309.150 25 O 268.250 309.250 P 268.350 309.350 Q 268.450 309.450 10 N 269.650 310.650 25 O 269.750 310.750 P 269.850 310.850 Q 269.950 310.950 11 N 260.375 293.975 25 O 260.575 294.175 P 260.425 294.025 Q 260.625 294.225 12 N 260.475 294.075 25 O 260.675 294.275 P 260.525 294.125 Q 260.725 294.325 13 N 261.575 295.175 25 O 262.075 295.675 P 261.625 295.225 Q 262.125 295.725 14 N 261.675 295.275 25 O 262.175 295.775 P 261.725 295.325 Q 262.225 295.825 15 N 261.775 295.375 25 O 262.275 295.875 P 261.825 295.425 Q 262.325 295.925 16 N 261.875 295.475 25 O 262.375 295.975 P 261.925 295.525 Q 262.425 296.025 17 N 263.575 297.175 25 O 263.775 297.375 P 263.625 297.225 Q 263.825 297.425 18 N 263.675 297.275 25 O 263.875 297.475 P 263.725 297.325 Q 263.925 297.525 19 N 243.915 317.015 5 O 243.995 317.095 P 244.075 317.175 Q 244.155 317.255 20 N 243.925 317.025 5 O 244.005 317.105 P 244.085 317.185 Q 244.165 317.265 21 N 243.935 317.035 5 O 244.015 317.115 P 244.095 317.195 Q 244.175 317.275 22 N 243.945 317.045 5 O 244.025 317.125 P 244.105 317.205 Q 244.185 317.285 23 N 243.955 317.055 5 O 244.035 317.135 P 244.115 317.215 Q 244.195 317.295 24 N 243.965 317.065 5 O 244.045 317.145 P 244.125 317.225 Q 244.205 317.305 25 N 243.975 317.075 5 O 244.055 317.155 P 244.135 317.235 Q 244.215 317.315 26 N 243.985 317.085 5 O 244.065 317.165 P 244.145 317.245 Q 244.225 317.325 27 N 248.845 302.445 5 O 248.975 302.575 P 249.105 302.705 Q 249.235 302.835 28 N 248.855 302.455 5 O 248.985 302.585 P 249.115 302.715 Q 249.245 302.845 29 N 248.865 302.465 5 O 248.995 302.595 P 249.125 302.725 Q 249.255 302.855 30 N 248.875 302.475 5 O 249.005 302.605 P 249.135 302.735 Q 249.265 302.865 31 N 248.885 302.485 5 O 249.015 302.615 P 249.145 302.745 Q 249.275 302.875 32 N 248.895 302.495 5 O 249.025 302.625 P 249.155 302.755 Q 249.285 302.885 33 N 248.905 302.505 5 O 249.035 302.635 P 249.165 302.765 Q 249.295 302.895 34 N 248.915 302.515 5 O 249.045 302.645 P 249.175 302.775 Q 249.305 302.905 35 N 248.925 302.525 5 O 249.055 302.655 P 249.185 302.785 Q 249.315 302.915 36 N 248.935 302.535 5 O 249.065 302.665 P 249.195 302.795 Q 249.325 302.925 37 N 248.945 302.545 5 O 249.075 302.675 P 249.205 302.805 Q 249.335 302.935 38 N 248.955 302.555 5 O 249.085 302.685 P 249.215 302.815 Q 249.345 302.945 39 N 248.965 302.565 5 O 249.095 302.695 P 249.225 302.825 Q 249.355 302.955
* Uplink frequency is super high frequency from 7.9 to 8.4 GHz on channel 1.
After this extensive list of channels and frequencies I want to provide a brief overlook of the military satellite systems currently in use. These list is far from being complete as it is quite difficult to find proper information about military satellites. WUN readers are invited to provide me further information and comments which I will gladly compile to another paper.
NATO IV Satellites
The NATO IV satellites are designed to meet NATO's requirements for integration of the SATCOM element into the NATO Integrated Communication System (NICS).
NATO first became involved in satellite communications in the 1960s. In the mid-1980s NATO decided to replace its third generation system with a new series of satellites based on the UK-built Skynet 4. As a prime contractor British Aerospace Space Systems (now part of Matra Marconi Space) was appointed in 1987.
The NATO IV satellite is of a modular design and comprises a service module and a communications module. Both modules are powered by two solar arrays which rotate about their longitudinal axis to face and follow the sun.
The satellite has a launch mass of 1430 kg and a dry mass of 731 kg.
The communication module comprises three SHF transponders, each of 40W power, providing bandwidths from 60MHz to 135MHz and two 25W UHF transponderseach one serving a channel of 25kHz bandwidth. SHF antennas provide footprints from spot to full cover. The UHF antenna is a earth-cover helix.
NATO IVA was launched 07. January 1991 and NATO IVB was launched 07. December 1993.
(Jane's Military Communication, 19th Edition, 1998-99)
UHF Follow-On (UFO) Communication Satellite
The UHF Follow-On (UFO) Communication Satellites began replacing FLTSATCOM and LEASAT satellites in 1993. As the UFO satellites are compatible with FLTSATCOM and LEASAT existing ground terminals remain usable.
The satellites weigh around 1170 kg with the UHF payload and 1350 kg with the additional EHF package.
UFO satellites have 11 UHF amplifiers and 39 UHF channels with a total of 555kHz bandwidth. 21 narrowband channels at 5kHz each, 17 relay channels at 25kHz.
(Jane's Military Communication, 19th Edition, 1998-99)
Milstar Satellite Communication System
This satellite shall just be mentioned as it containes according to Jane's Military Communication only EHF packages which is outside the scope of this column.
Leasat Communication Satellite
Leasat satellites (5 in total) are 4,26m in diameter and 6,17m high with its UHF and omnidirectional antennas deployed. The satellite weigh was 1388 kg. Leasat satellites were built by Hughes Space and Communications Company and were designed exclusively for launch on NASA's Space Shuttle.
Two large helical UHF antennas were used to provide communication service in the 240 to 400 Mhz band. The main communications capability was provided by 12 UHF repeaters.
In early 1997 the Leasat satellites were retired.
(Jane's Military Communication, 19th Edition, 1998-99)
FLTSATCOM
The Fleet Satellite Communications System was initiated 1971 by the US Navy to provide tactical multichannel UHF communication. It is also used by US Air Force bombers and launch control centres, all airborne command posts, and some US Army nuclear capable force elements.
The FLTSATCOM System has 23 channels in the 244 to 400MHz range (for details see the Military Standards section), wide band channels for Navy relay communications, narrow band channels as part of the AFSATCOM system and one 500kHz wideband channel used by the National Command Authorities and one 25kHz channel for fleet broadcast.
Each of the satellites weighs 912 kg with approx. 5kW radiated power.
(Jane's Military Communication, 19th Edition, 1998-99)
Receiving Tips
As most of the scanners are covering the frequency range between 200 - 400 MHz it should be no problem to enter the field of military satellite communications. Depending on what kind of antenna you are using the signals can be weak, so it's a good idea to do the first tune over the satellite communication band without any squelch in use. For the people using good antennas (maybe together with an amplifier) and a high quality scanner (like an AOR AR5000) its quite easy to detect a lot of signals with squelch in use. As soon as you are receiving a signal you can try to adjust the squelch to a proper threshold.
When it comes to the antenna it becomes a little bit more complicated. As you will in most cases only succeed with a directional antenna you should have of course clear sight towards the satellite. There are enough satellite tracking programs on the Internet freely available (e.g. STS Orbit Plus from David Ransom; http://www.dransom.com) to show you the exact position of a satellite regarding to your specific location on the globe.
Listening to a signal and you are not quite sure whether it is a sat signal or not? It is always a good idea to have a second receiver connected to an omnidirectional antenna at hand. This gives you the opportunity to differentiate satcom signals from local signals. If only the receiver with a directional antenna pointed towards a satellite position can hear the signal you can be quite sure to listen to satcomms. If your second receiver also gets the signal it's very likely not from a satellite.
Equipment tips
There is an old saying that an antenna which is still standing after a storm was just not large enough. Similar goes for the equipment of a monitoring post. You simply can't get enough. Some people really interested in doing military satellite communication monitoring are always on the look for professional equipment. And what kind of equipment can be more professional than phased out military equipment? This can be found for example at Helmut Singer Elektronik (http://www.helmut-singer.de/) and of course at Ebay. Phased out military sat comm equipment can also be bought quite cheaply on HAM fests as well as direct from the military disposal units for surplus material. Especially the sat comm equipment is often given away for a price per kilo. The reason is that most people and companies which are buying surplus material from the government are not looking for electronic gadgets and gizmos but more for standard personal equipment which can be easily sold in shops. Thus the circle of interested persons is usually quite small.
From my own personal experience I can only recommend to look out for surplus material for the low price and the high quality.
Identifying military communication equipment is easier today than one might think. The publishing house Jane's Information Group (http://www.janes.com/) is issuing once a year "Jane's Military Communication" which is a book (800+ pages A4) listing the military communication equipment actually in use worldwide. This book does cover all aspects of military communication and should be part of every monitoring shack. The backdrop is the price of the actual edition (beyond 500.-USD) but even these books can be bought over surplus channels or at stock clearings for 50.- Euro if they are two years old or older.
Antennas
As the standard rubber duck antenna will not work you will need a directional antenna to catch the signals. Not a perfect solution but an idea to start with is a channel 12 tv antenna which originally covers 224MHz up to 230MHz. A tv antenna is cheap to buy and is working also quite well between 240 - 260MHz.
Also good results can be achieved with a LogPer antenna (200 - 900MHz or 100 - 1300MHz). Such an antenna can be found for approx. 80.-Euro at Ham fests. This antenna is about 1,70m long and relatively easy to handle. The advantage of this antenna is that it covers a wide range of frequencies and can also be used for other monitoring purposes.
For best results with the least signal losses it is recommended to use helical antennas. These antennas can be bought from HAM suppliers but unfortunately they are quite expensive and usually only for HAM frequencies available. Another possibility is to use homebrew helical antennas for the specific military satellite communication frequency area.
Always a good idea is to employ a signal amplifier at the antenna. This amplifier allows to boost weak signals and compensate signal loss through long antenna coax cable. Unfortunately these broadband amplifieres a quite expensive, but there are enough tips on the Internet available for people who like homebrew equipment. Especially when suboptimal antennas are used it is recommended to use a signal amplifier.
Further Readings
In times where everybody can search internationally for books in databases and online shops like Amazon, it shouldn't be the big problem to find proper readings about satellite communication systems. Nonetheless I want to give some hints about books you should read.
As already mentioned before Jane's Military Communication should belong into every monitoring shack. Another interesting Jane`s publication is Jane's Radar and Electronic Warfare Systems which contains also a lot of satellite equipment.
Artech House Publishers is a very good source for satellite communication books as this publisher is speciallized in books about professional communication systems (www.artechhouse.com). One of the books I would like to recommend is Satellite Communication Fundamentals from Artech House Publishers. The book gives a detailed in depth insight into all details of satellite communications including the neccessary physical basics of satellite technology together with the mathematical models and formulas.
Also worth to mention are
- Satellite Broadcast Systems Engineering written by Jorge Matos Gomez
- Mobile Satellite Communications written by Shingo Ohmori
- Low Earth Orbital Satellites for Communication Networks written by Abbas Jamalipour
- Introduction to Satellite Communication written by Bruce Elbert
- The Satellite Communication Ground Segment and Earth Station Handbook written by Bruce Elbert
I hope this paper provided some usefull information for the hobbyist when it comes to military satellite communications below 500MHz. I invite your suggestions for revising or extending this paper. I plan to review and revise this paper as the need arises.
Copyright (C) 08/2003 by Howard Fuhs