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Saturday, July 17, 2010

Radio Communications

A handheld VHF/UHF transceiver, 2007.Image via Wikipedia
Every natural and manmade disaster to date has overwhelmed the communications capabilities of both the private and public sector in the affected areas. This is something that just happens. Everyone thinks they have to contact their family/friends/whatever NOW to make sure they're ok, and the phone system gets clogged. Things start happening quickly and need responding to, so all of a sudden 911 systems are overwhelmed, as well as the radio networks for emergency services now have tons more traffic due to tons more situations requiring some level of response.

What this means is that your most obvious standard communication methods will most likely fail.

What's non-standard for the majority of people? Radio.

There's tons of different radios, for tons of different frequencies. Some reach further than others, and some are more expensive than others.
Lets go over them and figure out what they're good for.

FRS Handhelds:

These are your run of the mill Walmart Motorolas or the like.
They typically get at BEST 5 miles of range under good conditions with fresh batteries. To get that range you need Line of Sight, meaning you need to have a clear path from you to the other radio.
The meager range is caused by the fact that they have weak power, limited amount of channels, and any asshat can go buy one.
What this means is that while you're trying to hold an important conversation with someone, chances are tons of people are listening, and you're probably going to have some kids playing hide and go seek start fucking with your comms.
They most likely take either a proprietary battery pack, or use AA's. They only put out a half watt, so their range is weak compared to basically everything else.
They are relatively easy to interface with for various handmikes and earpieces if you are so inclined.

Good use: limited local communications ie if you have friends and are moving an area no more than a couple blocks apart.

GMRS Handhelds:

More expensive
Require an 85$ FCC license so you and your family can use them
5 watts on handheld which ends up being about 20 miles of range on a good day
More often than not use a propriatary battery, not AA's.
You can get a repeater on these plus some base stations but generally speaking you'll most often only find handhelds. You have specific channels (frequency allocations) that you can use. These channels are generally also shared with FRS radios, and as such you can still run into Jimmy and Jeffy camping out in their backyard.

Use is about the same as a FRS with a bit more range. 10 miles on a good day, handheld to handheld.

Citizens Band:

CB radios are in basically every semi truck on the highway, and as such you have every trucker on the highway talking on them.
The advantage of this for inter/intrastate travel is that you can find out how things are in other areas... if you run into friendly people on the air. Good luck.
Handheld CB's are somewhat rare these days, most often you will find mobile units and that's it.
You can only put out 4 watts of power legally, but there are truckers with kilowatt amplifiers talking for miles and miles...
Range changes on atmospheric conditions. I have talked 100 miles in the lower 48 before, but you're lucky if you get a mile in Alaska with them.

You are restricted to 40 "channels" of specific frequencies. That's it. You can do sideband and push a smidge more power but the fact still remains that it's 40 channels anyone can get on, with a limited range

Good use: vehicular communications for road trips with maybe one hill beyond line of sight between vehicles.

Please note, none of the above actually have any encryption capability, legal or otherwise.
Amateur Radio

Ham radio ie Amateur Radio is an advanced method of communications over a significant range of frequencies.
These frequency allocations and capabilities differ depending on the license that you have with the FCC.
You and you alone take the tests and get authorized through your license to be able to talk on specific bands.

There are 3 licenses that are currently available in the US to be able to test out for:


Technician class gives you limited High Frequency transmission capability, but offers you VHF and UHF...
those in themselves are well worth getting your tech license.
A weeks worth of online study will end up getting you your license, the test is free to take

General class gives you a much wider capability with regards to High Frequency, Extra is just that.. a smidge more bandwidth and a much harder test.

Lets go over some radios that pretty much run the gamut of what Ham Radio can offer. These are the radios I personally own and use on a daily basis
Handheld Amateur Radio

For a handheld unit I personally own the Yaesu brand VX-7R.

This radio is protected against water ingress by a wide array of rubber gaskets and other weatherproofing techniques. It is rated for 30 minutes of submersion at a depth of 3 feet (JIS-7), plus a tough magnesium body with rubber bumper pads, making it ideal for outdoor use. Plus you get Dual Receive, 50/144/430 MHz operation plus wide-band receive coverage, a full color status indicator Strobe, and an "Internet" key for quick access to the exciting new WIRES™ repeater-internet linking system.
The VX-7R case, keypad, speaker, and connectorts are carefully sealed to protect the internal circuitry against water damage. And the optional CMP460A Speaker/Microphone, like the transceiver itself, is rated for 30 minutes of submersion at a depth of up to three feet.

The VX-7R provides a full 5 Watts of power output on the 50, 144, and 430 MHz Amateur bands, with bonus coverage of the 222 MHz band at 300 mW (USA version only). And for 6-meter AM enthusiasts, you also get 1 Watt of carrier power on the 50 MHz band. Four power levels may be selected, each offering its own degree of battery conservation.

The VX-7R is capable of four modes of Dual Receive, including simultaneous reception of (1) two VHF frequencies; (2) two UHF frequencies; one VHF and one UHF frequency; or one "general coverage" frequency and one "Ham" frequency.

And you can set up the VX-7R to reduce the audio level on the "Sub" band, if you like, when a call is received on the "Main" band.

The Most Memories Ever

Sporting the most memory capability of any Amateur transceiver, the VX-7R includes over 900 memory channels, yet access is simple and intuitive, thanks to the 8-character labeling capability. These memories include 450 "regular" memories, 10 "One-Touch" memories, 40 programmable band-edge-limit memories 12 "Home" channels, 10 Weather Band memories, 89 Shortwave Broadcast preset memories, 280 Marine channels, and 10 "Hyper" memories that store complete transceiver configuration data.

What this all means is that you have a waterproof radio in a small form factor ie pocket size, that can listen to a TON of shit, can either use external power, an AA battery pack, or various rechargeable batteries.
This radio can use external antennas. With the handhelds I mentioned above, you are stuck with the stock rubber duck antenna that is a huge limitation. By being able to swap antennas, you can vary the abilities of the radio.

You can use this radio with a hand-held antenna to be able to talk to Amateur Satellites in orbit, if you so desire.

I currently have this exact radio hooked up via a cable, to a mobile antenna on my car. This means that a 5 watt radio now can talk for 35+ miles easily, all depending on the terrain and obstacles between the transmitter and the reciever. I talk to the wife while she's on her way to work or on the way home from the house, with ease. You also can... modify it, to be able to talk on "other" frequencies if you so desire. Handy option.

There are other handhelds which have extended capabilities compared to this radio, but the VX-7 is pretty much the only handheld radio I would recommend for no other reason than it's more ruggedized and waterproof compared to all other handhelds that are on the market for ham enthusiasts. Battery life is good even on the rechargeable stock battery packs.

Mobile Amateur Radios

I own 3 mobile radios. The Kenwood TM-D700A, TM-D710A, and a Yaesu FT-857. Don't let the mobile designation fool you, you can actually use these with a power supply as viable and adequate base stations. Actual Ham base stations are pretty advanced and honestly are beyond the scope of what most people would need to be able to conduct reliable communications.. plus with a mobile radio, it's easy enough to rig up a seperate power cable so that you could use it in a mobile role via clipping onto a car battery for mobile or stationary remote use.

The TM-D700A and D710A basically are close to the same thing with regards to actual radio interface and design. They have dual tuners, with one capacity to transmit on either band. They only cover 144 and 440 mhz bands, but they put out around 50 watts on those bands. With a mobile antenna, I have been able to talk over 90 miles on VHF to individuals and repeaters reliably. The interesting thing about these 2 radios, is that they can do Packet radio as well as APRS (Automatic Packet Reporting System).

Packet radio is using your radio to conduct data transmissions. I have and do hook up a laptop to either of my Kenwood radios and do data transmissions.. you can do chat via text, send messages and the like. The interesting thing about packet radio is that most of the Radio modems IE Terminal Node Connectors (TNC's) have a mailbox built in... the advantage of THIS is that you could leave your radio on, and if you had a coordinated frequency and someone connected to your mailbox by knowing your callsign, they could leave a message that you could read at your leisure...

The advantage of Packet, is that although it's transmitted in a standard protocol... unless you have a packet radio tuned to that specific frequency, all someone is going to hear is effectively the same sound you would hear back in the day when you were on the internet with your modem and picked up another line in the house. PRSQSHHHHHHHHHHHHHHHH... you get the point.

Automatic Packet Reporting System, is a method to be able to send short text messages as well as location information over the radio. The advantages of this are that you can broadcast your location in case of emergency or if you're lost, as well as simply be able to message someone a quick update, ie you're running late, be there in about 15 minutes... the possibilities of use for both packet radio and APRS are simply up to your imagination with regards to the actual utility of those options.

These radios also both pick up a significant amount of traffic outside their transmission capability. I regularily listen while I am driving around, to the public service (Police, Fire, EMS) radio frequencies. This lets me get a feel for what's going on in town and where trouble is at, so I can actively avoid stupidity from the masses. In addition, I monitor my local Fire freq because... I'm a firefighter, and knowing there's a fire going on before I get paged out can let me plan ahead and have a quicker response time when I do get paged out.
Base Amateur Radio stations

I personally currently use my FT-857 Mobile unit with a power supply as a base station. This radio is an "All Bander" which means not only can it do VHF and UHF, but every HF frequency that you can transmit on. It's a very nice radio and has more options of modes and capabilities than I currently use. I purposely buy radios that I can "grow into" with regards to capabilities so that I don't have to upgrade as often. I try to do that with everything, since it's always better to have something that is better than what you can accomplish currently... that way the only limitation is YOU, not your equipment.

Just like buying a sub-MOA rifle... you may suck right now, but at least you can know that it's not an equipment failure, you just need to work on your accuracy... or a match grade pistol, every non-x ring hit, is your fault.

Let's go into Frequencies and capabilities.
Frequencies and Capabilities

For the amateur radio operator you have a huge amount of frequencies varying in characteristics.

Generally speaking, anything above 6 meters (the actual length of one full wave on the start of that band) is considered to be VHF. These transmission frequencies will ignore the atmosphere, but are generally known to be limited to direct line of sight for range.. so if you can't generally see where you are trying to talk, it ain't gonna get there. UHF ie 400 mhz and above, has the odd capacity to sometimes bounce around in mountains and such. The bandwidth from VHF and UHF lends itself very well to higher data rate transmissions for digital modes. Part of the reason that Wi-fi is on 2 mhz and above is specifically because you can get more data across in those bands, than if you were using lower frequencies. Smaller wavelengths directly correlate to more information being capable of transmitted in the same duration of time.

High Frequency ie 29hmz and below, depending on the atmospheric and solar conditions, will bounce off the Ionosphere of the planet. What this means, is that you can get "skip" and be able to communicate LONG distances with these radios. I can hear Japanese and Russian radio stations from where I am in alaska, and have made communications with my uncle in california in the past. Just because they skip doesn't mean you can't use a HF radio for short range communications... You can do Near Vertical Incidence Skywave... what this is, is adjusting or building a specific antenna that throws ALL the power basically straight up... Giving you about 300-700 mile range, and not needing line of sight.. as long as you can see the sky, you should be able to make good communications if you have a good antenna.

The largest limiting factor for all radios is the antenna. To transmit reliably, you need to have an antenna that is for the specific frequency you are trying to transmit on. You can use external tuners to trick your radio into thinking it has a good antenna. The importance of a good matched antenna is that there is a standing wave ratio (SWR) for the cable and antenna. If you have excessive SWR, it means you're storing power in the antenna which then can either damage the radio, or cause you to get shocked if you either touch the antenna, or your radio itself. It's important for all radios to have a good SWR match, preferably 1:1.5 or better. A SWR of 1:3 is bad enough that most newer radios will recognise and refuse to transmit because you could damage your equipment or injure yourself with the shock, depending on the power you're putting out. All antennas simply concentrate the radio frequency radiation in some manner, and that is how they provide "Gain".

My HF antenna is simply about 100 foot of wire that's strung on my property. It's unobtrusive, and I can take it down and reconfigure it for NVIS if I desire. My VHF/UHF Dualband antenna is currently a mobile antenna, that is on a base station base with ground plane antennae that protrude from the base. I can pull both of these down if I decide that I need to move my base station.

I honestly believe that studying up to and getting your General license, plus getting a HF capable radio, is one of the best investments that you could make in your own future... for one, it's interesting stuff to be able to talk to foreign countries, it's a reliable means of knowing what is going on around you, it will function when other normal communication means fail.

More avid HAM enthusiasts will put up Repeaters. What these are is a special radio unit that recieves on one frequency and retransmits on another. The advantage of a repeater is that it's typically a stationary unit, with a GOOD antenna, in a GOOD location... mountaintop and the like... This repeater lets you communicate from your position, to the entire area that the repeaters transmissions can be recieved... I've hit repeaters from a hundred miles away, and this let me talk to someone that was almost 200 miles from my actual location. Repeaters also sometimes have what's called an Auto Patch capability. THis means that it has a phone line hooked into it, and you can dial out for phone calls using your radio, if you have a tone equipped radio to transmit the number tones to dial a phone. This comes in handy when you don't have cell reception but can still hit a repeater, and I personally have had to use it to call police on ocassion when my cellphone battery died trying to call 911. VERY handy and is a wonderful thing to have in your area.

There are clubs that can teach you a lot more, offer classes to help you get your license, and are all interested in different aspects of radio. Some are into HF radio, some like doing microwave radio, some like doing Amateur Satellite radio, and some like doing Earth-Moon-Earth radio... and yes, you can communicate by bouncing radio waves off the moon. The versatility of amateur radio is pretty much limited to the imagination of the individual holding the hand-mike...