There are many free to use communications satellites for use only by licensed amateur radio operators, more are launched almost every year with more capabilities. Not licensed? Call the ARRL’s toll-free number at 1-888-277-5289 and request an informational Amateur Radio prospect package. You only need to pass a 35 question Technician exam which uses questions from a public question pool and usually pay less than $15 for an exam seat to begin using the Amateur Satellite Service along with free access to the expansive terrestrial repeater network and Morse code on several HF bands, more when you advance in level. Does this sound like a better deal than the $85 to get a GMRS license?
I suggest a solid state HF radio as the most durable and reliable method of long range communication in an emergency, but for portability reasons and those times where HF skywave or skip under or overshoots where you need to talk there is the Amateur Satellite Service.
There are three types of satellites; linear transponder, FM voice, and digital. I have already written in SurvivalBlog about the AO-7 linear transponder satellite. There are several others with many more capabilities, the high flying satellites like the currently dead AO-40 or Phase 3D poor man’s geostationary satellite had several transponders on many bands including microwave and would be overhead for several hours a day. Current FM voice satellites are the easiest such as AO-51, AO-27, and the International Space Station. They work mostly like a regular local radio repeater but cover most of a continent or span an ocean, you just need to deal with the Doppler effect. Digital satellites are either digipeaters or a space based computer BBS mailbox, they require a Terminal Node Controller (TNC) or computer with the right software and sound card. A few of these satellites and the space station combine several of these modes.
This article will concentrate on FM voice satellite operations since this is how most of you will start out since it is cheap and easy to access this service. More importantly it is easy for a person on foot, bicycle, ski, or on horseback to carry and power the gear to access satcom birds, easier and often more reliable than small QRP HF sets for trans continental communications.
Firstly you will need a radio, I have used Alinco DJ-580T and DJ-582 radios for satellite work but they need the large battery for full 5 watts or an external power supply. I know the Yaesu FT-470 and several radios by Icom and Kenwood were also 2meter/440 or 2meter/70cm dual banders, but it is reasonably important that they also be full duplex so you can listen even as you transmit allowing you to tune to your own repeated signal from the satellite. You can fudge and use a 5 watt 2m VHF radio for uplink and a scanner for the 440MHz or 70cm UHF downlink band, the trick is finding a scanner which tunes at 0.005MHz or smaller increments, this fine tuning is critical when we adjust for Doppler, more about that later. I have purchased good dual bander full duplex rigs go for around $50-75 used on eBay, or even less at radio swaps especially if they need minor repairs, are missing the antenna, or need a new battery pack, you can always just use an external power
their battery pack or you need to “re-core” the battery pack.
You also need a high gain antenna, the rubber duck antenna on your radio might be enough to hear the space station, but rare will be the day that you can work contacts on a satellite with just a rubber duck, although it has been done. I see web sites of people who use a telescoping whip but for the plane crash hero fantasy I would just use a roll-up twin lead J-pole antenna like this one. I use the twin lead J-pole for talking to my wife at home and keep one in my bike bag, but have never used it for satellite operations since it requires a stick to hold the antenna out straight. The best antennas for mobile operations are Yagi antennas made from aluminum tube such as the Arrow. it is used out of the box for satellite operations but it is very expensive. The very best antenna in my opinion is one you can build anywhere from stuff at a hardware store,
the Kent Britain Yagi designs are great, this PDF includes how to make a duplexer for splitting the 2m and 70 cm signals for their respective antennas.
For some pictures of these Kent Britain-type antennas and help with working FM satellites see these links featuring Diana Eng. This cute little fashion designer can hand build an easy Satcom antenna and turn the knob on a radio, so why can’t you?
My stick Yagi antenna looks like the second Diana Eng Make link except hers use brass and aluminum tube which is hard to find in Israel. I used steel 1/8 inch wire off the roll for the reflector and parasitic elements. I made the antenna from 10 AWG insulated copper ground wire for the actual radiating element. You can either buy the BNC connector at Radio Shack and attach it to the 50 ohm co-ax or get the radio guy at the truck stop to make your custom cables. You will have to solder a bit to attach the feed line cables to their radiating elements but that should be easy. The Kent Britain PDF also shows how to make a simple duplexer with some coils of wire wrapped with a pencil, some 50 ohm RG-58 co-ax, a square of copper or brass, and four 4.7pF capacitors (available from Radio Shack.)
Operating involves knowing when the satellite is overhead, tuning to match Doppler, and trying to make a voice contact.
Knowing where the satellites are either involves knowing the orbital period and spending a few hours scanning then recording which passes are above the horizon and heard, between a week and ten days the pattern will repeat, now you can mark your calendar into the future with this pattern. Know how to track with a watch calendar and some math but if you are more prepared using a PDA or computer with a satellite tracking program installed is much easier and saves time. Here are the TLE Keplarian elements listings to feed to the programs and a list of programs for many platforms I use Gnome Predict on my Ubuntu Linux machines, and PetitTrack on my tough old 2003 vintage Linux Sharp Zaurus 5500 pocket computer/PDA. Remember that a pass is usually only ten or twenty minutes with the low earth orbit birds longer on a hilltop and quite short in a deep valley where you can only catch very high passes. Draw the acquisition of signal and loss of signal times, appearance compass bearing, frequency up and down links, and sky path on a chalk or white board that you can reuse and not endanger your computer to the elements or breakage.
For the current FM sats the uplink is on 2 meter band which doesn’t require Doppler adjustment, just punch in the published frequency, but on the 70cm receive band you will need to tune for Doppler frequency shift between 5-10khz(0.005-0.01Mhz) over the published frequency as the satellite approaches your position and tune 5-10 Khz under as it flies away, pretty much when the computer says the satellite is over the horizon sweep your antenna where it is supposed to appear and tune around the Frequency range with the squelch open until you will hear static quieting or radio traffic, possibly your own test calls bounced back. See, it’s not hard five clicks; one for far approach, one for near approach, one for overhead, one for passing, and the last click for far passing on most radios. This Doppler shift is due to the satellite moving fast enough to cause a minor, yet noticeable shift! Get the operating frequencies for the satellites you plan to use, include alternate modes and write them in your pocket notebook in case you have no computer. Here are links are for the AMSAT status page, AO-51 schedule page, the AO-27 page, and the International Space Station page. These will help you quickly find the current operating mode of the satellite, you might even get to chat with astronauts or cosmonauts on the ISS or Shuttle, just like in the novel Lucifer’s Hammer
Once everything is set and the satellite is over I first listen for other operators, it is rude to talk over other operators. The first few passes as you learn just listen to how people talk on the satellite. Some sats require a PL tone to activate them, just like many Earth-based repeaters, look in your radio operator manual to set that. Evenings and weekends in North America and Europe the satellite will be jammed with people leaving you enough time to say your callsign for training and get a reply, no chatting, if you have an emergency say mayday everyone will quiet up. In low population areas of the south seas you might rarely make contact, keep trying. During an emergency don’t play with the sats just listen as they will likely be used by Amateur Radio Emergency Services or other groups supporting FEMA or state relief efforts. I have best success listening with full ear cup headphones, I run squelch open and know I am getting close to getting the signal as the receive band random static quiets down.
If at all possible record both sides of your satellite conversations but more importantly received transmissions, use a Y-splitter and plug the recorder in a full duplex radio will get your signals off the sat too, chances are you missed something and want to rehear the conversation. Things go fast when you are on the satellite with talking, listening, tracking the sat, and Doppler adjusting. Digital and cassette recorders both have merits and downsides. Even smarter is to tape your message ahead of time ready to play on a second multi speed tape machine, once you make contact and the receiving station is ready play it back on squeaky fast speed if you have a long message. The other side can replay it normally by setting their player on slow speed. If you can’t put your message on tape have a script ready on your chalkboard. Remember that you will probably have less than 10 minutes of talk time on a good pass when nobody else is waiting to talk.
You can enjoy the amateur Satellite Service even before you are licensed by using your police scanner on the downlink frequencies, of course you still need to correct for doppler and use a high gain antenna.
Most servicemen know that only very special troops get equipped with the satcom gear. You can now include this special communications mode to your preps easily for less than $100 per complete unit. Impress your friends and educate your kids on physics and space travel while you prepare. This may sound hard, but so is making a telephone call or using a microwave oven until you someone shows you how, even a fashion designer could figure it out. – David in Israel