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Berenger
2013-07-02, 01:51 PM
They've done it, they've split the party. Like, across the USA. During the zombie apocalypse.

I'm in desperate need of a really simple description of radio communications, since this stuff is not exactly my forte. Luckily, I don't think it's the forte of anyone in the group, so I just need to avoid the most outrageous blunders. I guess I need to know:

a) Different types of radio devices (I know there are walkie-talkies and, well, bigger stuff).

b) Rough estimates of signal range of said devices (I know this changes with weather, terrain and evelation but I need some general idea to start with).

c) Dependence of said devices on a "third party" equipment (satellite (?), relais stations) and an estimation of how long these things last without maintenance.

d) How do different devices interact? For example, can a fancy cruise ship radio station with high range contact a simple low-range walkie-talkie and can the guy with the walkie-talkie answer?

Many thanks in advance...

NM020110
2013-07-02, 02:11 PM
Just be glad they didn't decide to go one player per continent on you...

Anywhy, this (https://simple.wikipedia.org/wiki/Radio) should help a little.

To try to answer your questions...well, I'm not qualified. Still, here's what I do understand:

a.) From what I got, you have receivers, transmitters, and transceivers (which, fittingly enough, transmit and receive). Transmitters likely require a power supply, while receivers...I'm not sure.

b.) For range, all that I saw on a skim is that it's a fair bit better than line of sight. Probably dependent on transmitter size.

c.) For across the US, you'll probably need relay stations or something. They'll probably last as long as they get power and aren't attacked...

d.) The smaller radio should be able to receive if it can tune to the right band. I'd figure range of transmission separately for the cruise ship and the walkie-talkie, then check to see what is in range.

I'd be sure to verify everything above, as there are probably inaccuracies.

Gnoman
2013-07-02, 05:27 PM
If you can find the necessary equipment (which is pretty easy to do in the civilized world, though an apocalypse could change that), a basic AM ham radio can transmit to and receive signals from extremely long ranges. In WWII, USFIP was communicating with Pearl Harbor and Washington (albeit intermittently) with a radio that they built out of scraps (IIRC, they cannabalized a movie theater for the parts) from the Philippines. At mere continental ranges, with very little signal interference, talking cross-country is fairly trivial. Plans for such can be found in pretty much any library, and complete sets are fairly common in specialty hobby shops. If either institution survives, then it's trivial to equip the party. Such a radio, however, isn't exactly portable. It'd be more like a high-end stereo system in size.

The only difficult part is making sure everyone has the same frequency (trivial if they can scavenge parts from a radio hobby shop or the many local AM stations that dot the country) and providing sufficient electricity. The latter is particularly problematic.

Ozfer
2013-07-02, 06:15 PM
A crank generator can solve the electricity problem. Of course, independent generators might be hard to find, but if the players are electronic-savvy they could easily convert crank-flashlights, tv's, etc... Or even just make one from scraps. Bicycles are valuable for charging-machines.

Slipperychicken
2013-07-02, 07:48 PM
What confusion of ideas could lead to such a debacle?

Ashtagon
2013-07-03, 08:29 AM
Any radio transmitter with a range more than a few miles will require a mains power supply (barring super-science batteries etc). Radio receivers can typically function well on battery power; some are designed to take mains or battery power.

Narrow-beam radio transmitters are possible, reducing power usage, increasing range, and making casual interception less likely, but they are very specialist military technology, and unlikely to be found in a post-apocalypse.

An ultra-sensitive (and mains-powered) radio receiver capable of receiving from a battery-powered transmitter is possible, but on Earth these only conventionally exist for the purposes of SETI, and are narrow-beam devices aimed at outer space. They can't sensibly detect signals from an Earth-based transmitter.

The range of shortwave radio is essentially global, as the signal bounces off the ionosphere and ground around the globe. Longwave radio however, doesn't bounce, and is limited to line of sight, traditionally broadccast from radio towers to increase range. It has the advantage of being more signal-dense (hence why it was used for early television).

Neither of the above really needs orbital satellites or cellnet re-transmitters.

Walkie-talkies typically operate on a specific range of frequency bands and have a very short range (few hundred yards for hand-held models, ranging to a few dozen miles for truck-mounted models). Assuming a building-based transceiver is re-jigged with a little elbow grease, it should be able to send and receive on those frequencies. There is no real hope of using a walkie talkie to send to a handheld radio receiver. Note that their transmitting range will limit their ability to send to a central station, although their receiving range would be to the full power of the base station. They also can't receive the short-wave global-range radio signals, so the base station would need to rely on a radio tower and line of sight.

Elvenoutrider
2013-07-03, 10:36 AM
Send a raven

Berenger
2013-07-03, 02:03 PM
What confusion of ideas could lead to such a debacle?
Well, it's a PbP and the "party" is rather large. It's done to make individual parties more manageable and avoid too much interaction between multiple characters of the same player.



Send a raven
Thanks for reminding me to send in the zOmBiE aNiMaLs. :smallamused:


Thank you very much, I think this will help. So, if I cannibalize a radio equipment from a fishing trawler and set it atop a wooden tower on a hill. I can send to similar stations and and modified walkie-talkies basically everywhere, but the walkie-talkies themselves can't answer, right?

Ashtagon
2013-07-03, 02:27 PM
Thank you very much, I think this will help. So, if I cannibalize a radio equipment from a fishing trawler and set it atop a wooden tower on a hill. I can send to similar stations and and modified walkie-talkies basically everywhere, but the walkie-talkies themselves can't answer, right?

With such a set-up, if you are using longwave radio then effective base-to-handset communication range is line-sight from the top of the tower. Using shortwave, effective range is essentially global. Handset-to-base range is limited by the broadcasting power of the handsets. With either type of transmitter (http://www.osha.gov/SLTC/radiofrequencyradiation/), the energy levels involved mean you will want them on a tower in any case - they are electrically live, and if ground-based, significant amounts of transmission power will be earthed and wasted.

However, with shortwave, range *is* global and broad-beam. So if an NPC group is around anywhere, they can listen in too once they tune in to the correct frequency. With longwave, it's still broad-beam (unless you modify your transmitter), but limited range.

The PCs could if they want, use longwave radio, and set a narrow or tight-beam transmission in order to reduce the odds of their communications being intercepted.

The next step up in secrecy is to encrypt the message, either by computer algorithm, or simple word substitution ciphers.

Presumably, the PCs could cannibalise parts to make base stations at multiple locations, get the bases staffed by NPCs, form an ersatz radio network for a global telecommunications renaissance, and then have adventures when one of the base stations unexpectedly goes silent.

Gnoman
2013-07-03, 04:25 PM
Any radio transmitter with a range more than a few miles will require a mains power supply (barring super-science batteries etc). Radio receivers can typically function well on battery power; some are designed to take mains or battery power.


Not true. radio in the right frequency takes a surprisingly small amount of electricity to transmit at huge ranges, because the signals bounce off the upper atmosphere. Plenty of military communications in WWII were sent across oceans from battery or bicycle generator, while the Apollo transmissions from the moon were sent on power from hydrogen fuel cells.

Ashtagon
2013-07-03, 05:09 PM
Not true. radio in the right frequency takes a surprisingly small amount of electricity to transmit at huge ranges, because the signals bounce off the upper atmosphere. Plenty of military communications in WWII were sent across oceans from battery or bicycle generator, while the Apollo transmissions from the moon were sent on power from hydrogen fuel cells.

My understanding was that the WW2 spy transmissions, and the lunar landing transmissions, were both received by virtue of very sensitive and very large radio receivers, rather than because of the power of the transmitter. Very sensitive receivers aren't all that common as post-apocalypse salvage. The only ones in modern usage are those involved in SETI and those designed to receive satellite transmissions. A consequence of this is that they are usually optimised to be direction-sensitive.

Gnoman
2013-07-05, 03:35 PM
There was some of that, but they're not nearly as necessary as you might think. The big problem with picking up a low powered transmission is signal interference. If you're trying to get past the local talk radio, you need a much more sensitive antenna or much more power. If most radio systems are down, then that's not a problem.

Zahhak
2013-07-05, 06:57 PM
A ham/amateur radio (the kind that we stereotypically associate with truckers) with an antenna can bounce radio signals off of objects to increase range. On a clear night an amateur radio operator can bounce a signal off of the moon and talk to someone on the far side of the planet. High cloud cover can be used to bounce signals across the country. This of course requires a bit of understanding of various fields, like climatology and how radio signals work, but its definitely possible. If your group has the time they could definitely find a shop that sells amateur radio set ups, which will have guidebooks for how they work. They will need to do some research on which ones to use though, since you'll need a radio that can go into ultralow frequency (ULF) to do this. Amateur radio in in the US is tightly regulated, and ULF radios require special licenses, so they'll be harder to find.

As for power, you only need three things to make electricity: a coil of ferrous (magnetic) metal, a magnet, and relative motion. If you've ever seen an emergency flash light you know exactly what I'm talking about: all that is is a coil of some kind of steel, a magnet, and your hand providing the power. You could easily rig up a similar system for an amateur radio. Or you could go with the hand cranks that a few people have been talking about. You might even be able to find hand cranks specifically designed to power amateur radios, since people will take them with them when they go into mountains and such. Oh, and most amateur radios run on batteries.

You can probably find out all of the information you could ever want to know on amateur radio and more by looking for your local amateur radio group. They're often extremely friendly people.

Berenger
2013-07-06, 06:55 AM
Thank you all very much, I think this knowledge will suffice for our purposes. :smallsmile:

Radar
2013-07-06, 09:06 AM
About hand cranked generators and the use of the electricity produced: they don't produce stable voltage. What you'll probably need to make the radio work properly is a solid accumulator (car battery would do, but it's quite cumbersome to move around).

Also worth mentioning:
1. Power usage is also related to the width of the frequence band you emit. If you menage to build a high quality emmiter and reciever (as in able to tune in for a very narrow frequency band), then you will save up on electricity use and increase the reliability of your radio.

2. If you don't know, where to find an antenna, you can just plug into the lightning conductor or pipe system of any high building. Pretty much any big metal structure would work.

Mark Hall
2013-07-06, 09:11 AM
It's also worth noting that one advantage of the zombie apocalpyse is that there will be less interference... while more people will be using AM radio, there won't be nearly as many people transmitting as there are stations right now, and you'll be able to "move down the line" if your chosen frequency gets busy.