One problem that most preppers fail to take seriously is communications. To most First Worlders communications are something that comes out of the wall like water or electricity, so why should the magic ever end? While not as high a priority as an inexpensive firearm for security, food, water, cooking fuel, non-motorized transport, or shelter, in a safe area communications with those you care about keeps you from going on unneeded health and welfare checks especially during dangerous times.
Typically I would suggest a 100 watt+ multi-band HF radio for vehicle or base use and a QRP 40meter set and/or 2m/440 handi-talkie and home made Yagi antenna for lightweight sat-com for those who must travel or bug-out long distances on foot, ski, horse, or bicycle.
There are circumstances which can impair HF radio such as nuclear detonations, and in an information age warfare situation even amateur satellites can be hacked via their encrypted command channel and shut down temporarily. There is one tough old bird, designated AO-7. It is back from the dead and still in orbit which is for the most part immune to these troubles, possibly even toughing out a few nukes if it is in the right place at the right time. AO-7 is not the easiest satellite to work, so beginners might want to first try the FM birds. But what better satellite for a survivalist than the “reanimated” AO-7. [Insert mutant zombie biker jokes here.]
AO-7 was launched 15 November 1974. It remained operational until a battery short killed the satellite in 1981. On 21 June 2002 the battery short finally opened up and the satellite was heard again on its 2 meter beacon (145.9775 MHz CW) after 21 years of silence, and 27 years in space.
What is bad about the current situation is that power is limited, only a few concurrent CW, SSB voice, or low bandwidth data transmissions are possible before the transponder draws more power than the large but aging solar cells produce resetting the satellite. The good news is that as far as I can tell even if the satellite command channel is somehow hacked it will only be shut down for a short time when it is in eclipse and powers down or when the transponder is overloaded and an undervoltage resets the satellite. For a few months twice a year the satellite is in full sun 24 hours a day and alternates between mode A, B, and C.
One last bit of info for those who have only worked terrestrial Amateur radio contacts or possibly even FM satellites and the space station, this is not so much a repeater in the sky where one guy takes turns on the whole thing, it is more like a snippet of frequency that is picked up by the satellite amplified and retransmitted on another band, many people can squeeze in and use, much like on HF. This is why SSB or CW are important modes to use minimizing wasted retransmitted bandwidth. You might get the transponder to beam back FM or wide band data but it is not acceptable to push several other conversations off a satellite so you can be a hog, on AO-7 it would probably re-set the satellite anyway.
If you are not a ham you can pick up this and the other satellites using your a scanner that has SSB abilities, sometimes you also need a better antenna than the standard “rubber duck” [whip antenna] to pick up the signal. Kent Brian is an antenna genius. Get his free instructions for portable pocket change sat-com antennas.
You will also need to track the satellite, the easy way is with a computer program for your laptop, phone, or PDA that uses a NASA/NORAD two line [descriptor] element for the Keplerian elements so you can tell when the sat will be available and how much the Doppler will bend your frequency. There are plenty of free tracking programs. BTW, it is fun for kids to spot satellites and the space station even if you have no itch for satellite communications.
this is the TLE for AO-7:
1 07530U 74089B 10117.60551541 -.00000027 00000-0 10000-3 0 7622
2 07530 101.4026 135.4310 0012225 014.2326 345.9087 12.53578232622114
If you are working with only a watch, pencil, and paper remember that not every 115 minute orbital pass is above the horizon for you. And only once or twice a day do you get a sweet high overhead pass good for line of sight from valley locales. If you keep a listing of passes in a notebook you will notice a repetition in about a week to 10 days for the amateur sats, now you can extend the repetition pattern indefinitely into the future. Here is a summary that I found at the AMSAT web site:
Orbit: 1444 x 1459 km
Inclination: Inclination 101.7 degrees
Period: 115 min
Beacons:
29.502 MHz (200 mw) Used in conjunction with Mode A
145.972 MHz (200 mw) Used in conjunction with Mode B and C [low power Mode B]
435.100 MHz (intermittent problem — switches between 400 mw and 10 mw)
Linear Transponders:
Transponder I: Mode A
Type: linear, non-inverting
Uplink: 145.850 – 145.950 MHz
Downlink: 29.400 – 29.500 MHz
Translation Equation:
Downlink (MHz) = Uplink (MHz) – 116.450 MHz ± Doppler
Output Power: 1.3 watts PEP (start of life)
Transponder II: Mode B and Mode C (low power)
Type: linear, inverting
Uplink: 432.125 – 432.175 MHz *See Note
Downlink: 145.975 – 145.925 MHz
Translation Equation:
Downlink (MHz) = 578.100 – uplink (MHz) ± Doppler
Output Power: 8 watts PEP Mode B (start of life), 2.5 watts PEP Mode C
Mode C, while weaker, is useful to us because it allows more operators onto the transponder before it goes to undervoltage and resets. An inverting transponder tunes the downlink frequency downwards as you tune upwards on the transponder uplink, non-inverting tunes with you.
When AO-7 first came back from the dead Jan King, W3GEY, the AMSAT-OSCAR-7 Project Manager commented: “AO-7 has a good set of arrays and the first BCR (battery charge regulator) we ever flew. It’s the first spacecraft we ever had that was capable of overcharging the battery. When the battery failed the cells began to fail short. One cell after another failed and the voltage measured on telemetry began to drop. So, the cells were clearly failing SHORT. Now, after all these years, what happens if any one of the cells loses the short and becomes open? Then, the entire power bus becomes unclamped from ground and the spacecraft loads begin to again be powered but, this time only from the arrays. Now you have a daytime only satellite but, each time the sun rises at the spacecraft you have a random generator that either turns on Mode A or Mode B or whatever it wants.”
Visit the AMSAT site for more information on working the satellites, and specifically their AO-7 page. Also, Emily Clarke has a nice AQ for working AO-7.