My purpose in writing this article is to focus attention on an area that is lacking for too many people. Having been in a group that did a lot of training, it became clear that this was an area that needed attention. We used email and cell phones to coordinate training location and times, but the thought was always in the back of my mind; what if there was no Internet or cell phones? How would we form up as a group? I have compiled the information into a simple, bullet-point scenario to make it easier to grasp and to focus on key areas. Also, there are exceptions to specific parts of this information, but for the majority of people it will apply.
- Radio waves are all around us.
- They transmit data, conversations, pictures, and music invisibly through the air over thousands of miles.
- It happens every day, and they have changed society.
- They control everything from cell phones to satellites.
- A few of the everyday items:
- Garage door openers
- Radio-controlled toys
- GPS receivers
- Baby monitors
- Microwave ovens
- Airplanes depend on a dozen different radio waves
- Frequency chart
- If I want to get this chart on one page, I can’t read many of the sections!
- There are hundreds of frequency categories.
- Electromagnetic waves start at a source and picked up at a destination.
- Travel near the speed of light.
- The higher the frequency, the shorter the wavelength.
- Frequency is measured in Hertz (cycles per second).
- Radio frequencies measured in;
- kilohertz (KHz) – thousands of cycles per second
- megahertz (MHz) – millions of cycles per second
- gigahertz (GHz) – billions of cycles per second
- Designing a system requires several categories to be checked off;
- Must operate over a certain distance = range
- Transfer a certain amount of info within a time frame = data rate
- Must do it economically = price
- Need to get government agency approvals (FCC) = regulations & licensing
- Range determined by;
- Transmit power; amount of RF power that comes out of the antenna port.
- Receiver sensitivity; the minimum signal the radio can receive.Example using sound;
transmit power = how loud someone can yell
receiver sensitivity = how soft a voice someone can hear
- Radio Frequency spectrum ranges from;
- VLF (Very Low Frequency) – 3kHz to EHF (Extremely High Frequency) – 300GHz
- All of the frequencies we are concerned with are in the HF, VHF and UHF bands.
- Nearby: VHF & UHF either direct or through repeaters
- Regional: VHF & UHF through repeaters
- Country-wide: HF direct, VHF & UHF via internet (unless it is down)
- World-wide: HF direct, VHF & UHF via internet (unless it is down)
- Total of 40 channels.
- Channels from 26.965 to 27.405 MHz (11 meter HF band).
- Reliable range is 5-10 miles but can be much farther with the right conditions.
- For use in personal and business activities of the general public.
- There is no age, citizenship, or license requirements.
- Can use any of the 40 channels, but channel 9 is used only for emergencies or traveler assistance.
- Usage of all channels is on a shared basis.
- Generally limited to 4 watts.
- Total of 15 channels.
- Channels 1-7 shared with FRS.
- Channels from 462.5625 to 467.900 MHz (just above the 70cm Ham band) in the UHF band.
- Range is normally 2-5 miles.
- Requires a license ($85 / 5 years) but no exam.
- Can transmit up to 50 watts but 1 – 5 watts is more common.
- Channels 1-7 shared with GMRS.
- Channels from 462.5625 to 467.7125 MHz (just above the 70cm Ham band) in the UHF band.
- Range is about 1-2 miles.
- Initially proposed by Radio Shack in 1994 for use by families, authorized in the US since 1996.
- Limited to 500 milliwatts (0.5 watts).
- Must use permanently attached antennas.
- Total of 5 channels.
- Channels from 151.820 to 154.600 MHz (just above the 2m Ham band) in the VHF band.
- Range is 2-5 miles.
- Total of 50 channels.
- Channels from 156.000 to 157.025 MHz (just above the 2m Ham band) in the VHF band.
- Limited to “on the water.”
- Range is about 20 miles.
- Receiver used to monitor police, fire and emergency medical services on VHF and UHF.
- Sequentially monitor multiple programmed channels or search between frequency limits.
- Stops on an active frequency and resumes scanning other frequencies when that activity ceases.
|CB||40||about 10 miles||4 watts|
|GMRS||15||about 2 miles||1-5 watts|
|FRS||14||about 2 miles||0.5 watts|
|MURS||5||about 5 miles||2 watts|
|Marine||50||about 20 miles||1-25 watts|
- It is the only form of communication when nothing else works.
- Can’t be controlled by government despite government involvement (FCC licensing, etc.).
- Can’t be shut down.
- Might be able to disrupt one frequency for a limited time in a limited area.
- Hams are routinely on air when there is no power.
- Have to practice. You won’t be able to just pick up a radio and be proficient. (If you’ve never fired a gun, you aren’t a sniper with the first round).
- Amateur radio has a tradition of “Elmers” – people who are willing to help.
- Radio to radio direct, known as “simplex.” Transmitting & receiving on the same frequency.
- Most VHF and UHF communication uses “duplex,” using two different frequencies “offset” for transmitting and receiving and often activated by subaudible “tones” through repeaters.
- Repeaters are powerful radios that, because of their prominent placement on mountaintops or tall buildings, facilitate wider range communication.
- Technician license covers both VHF & UHF.
- Both VHF & UHF are line-of-sight, short-range.
- General or Amateur Extra license needed.
- HF communications use simplex, not repeaters.
- HF doesn’t use channels (generally).
- HF has skip zone (dead spot) at roughly 75-300 miles.
- Military developed NVIS (Near Vertical Incidence Skywave) to communicate in the skip zone.
- Ham classes are often free, and run by volunteers.
- There are multiple websites to practice. (See below)
- Ham exams cost $15 (fee for the Ham examiner) and can often be taken more than once on the same day if you don’t pass.
- Technician exams are 35 questions out of a pool of 350 possible questions.
- Get a (the ARRL Ham Radio License Manual) manual for the Technician license. Ham Radio Outlet has them as do numerous websites.
- Generally 11 meters to 120 meters in the HF spectrum.
- Travels more reliably for longer distances.
- Often government broadcasts.
- Listen only.
- Known as a Tiger Tail
- Use on handheld radios to increase range
- YouTube Videos
- Wire: 19.5″ for 2 meter, 6.5″ for 70 centimeter
- Three Main Types of Radio Communication
- Short range – under 50 miles.
- Long range – state, country, and even worldwide.
- Scanning – keep tabs on what is going on around you.
- Power (watts) and number of channels are key.
- Ham radio is far superior to all other radio types.