from Survival Blog:
Today, we’re continuing to look at communications devices in this communications overview section of the article. So far, we’ve look at Ham radio/licensed devices, but now we’re moving into non-FCC license dependence communication devices to consider.
Cell Phones – Using During An Emergency and Improving Reception
During an emergency it is very common that the local cell phone towers become saturated. Many people attempt to connect at the same time, resulting in busy signals. In addition, some cell towers have special equipment that restrict public use and dedicate additional bandwidth to emergency services. This section covers how to get a message out, as long as the cell tower is working.
SMS texts (aka messages on an iPhone) use an alternate channel on cell phone towers called a control channel. This control channel is isolated from voice and data channels and is not impacted when too many voice and data connections are made. SMS also caches the message on your device and makes several attempts to deliver it, which is very useful if service is intermittent.
Because SMS is less impacted by cell tower saturation, it is more likely to send and receive messages. This is true even when you get a busy signal via voice, or standard data dependent applications like Facebook Messenger or Twitter will not work. It’s also important to note that because SMS uses a control channel on the cell phone tower, it is less impacted by bandwidth restrictions implemented by the government during an emergency.
In addition, when in an area with spotty cellphone reception, the packets sent via SMS have a higher level of reliability because SMS packets do not need to have a constant connection to the tower. Voice and data connections need to establish and maintain a connection to the tower in order to function. SMS connections are at send time only.
Cell Towers Operating in UHF Range
Cell phone and tower propagate or operate at frequency ranges from 700MHz to 1.9GHz, commonly referred to as UHF. What matters about cellphones operating in the UHF range is that UHF propagates using “line of sight”. LOS propagation means that the cellphone and the cell tower have to be within a range that is not impacted by the curve of the earth (about three miles). It also means that radio waves (UHF) can be bounced off some objects and can pass through others.
Take Advantage of UHF Propagation
You can take advantage of UHF propagation in the following ways:
- If you are far from your nearest tower, gain height. Try to make the call from the highest location you can.
- If you know the direction of your nearest tower, you can take advantage of hard objects, especially metal ones, by holding the cellphone very close to that object, with the cell between the tower and the hard object (brick/stone/metal wall of a building).
- You can create your own metal object by putting tinfoil on the back of the cell phone and pointing the cell phone screen at the tower. If you do not know where the tower is, you can add the tinfoil and rotate your cellphone until you have better reception.
- If you are adventurous, google “diy parabolic reflector cell phone”. This will show you many examples of using metal objects near the cell phone to increase your signal.
Useful Cell Phone Applications in Emergencies
There are a number of cell phone applications that are useful during an emergency. Below are some options:
- 5-0 Radio Police Scanner – (free iPhone application) allows you to listen to emergency services, locally and nationwide.
- Messages – (included iPhone application) SMS texting.
- Viber – (free iPhone application) network-based calls and messaging.
- Facebook Messenger free iPhone application) network-based text messages
- Twitter (free iPhone application) network-based text messages
- Echolink (free iPhone application; however, it requires a FCC Ham Radio License and call sign)
- MyAPRS (free iPhone application; however, it requires a FCC Ham Radio License and call sign) network and RF (Radio) text messages, along with GPS locations of sender and receiver. The built-in map shows locations of 2m/70cm/1.25m repeaters).
- PocketPacket (low cost APRS iPhone application; however, it requires a FCC Ham Radio License and call sign) with a cable to a HT (Portable 2M Ham radio). This can send text and position to other people running APRS. This can also be used to send texts via RF to Internet gateway servers, which can forward to remote cellphone SMS and Email. (More details covered in Ham Radio section.)
Marine Radio – (VHF)
These radios are similar in frequency to MURS. However, they are dedicated to operation in a marine environment.
Marine Radio has the following features/restrictions:
- No license needed
- VHF frequency range of 156 to 174 MHz with FM modulation
- 1-25 watts output
- Conditions over water extend radio waves
- Almost always submersible; check your model
- Monitored by the Coast Guard
- No antenna restrictions
- Illegal to operate outside of a maritime environment
MURS – (VHF) Multi-Use Radio Services
MURS radios are two-way, low power (2 watts), allows for removal of stock antenna and add-on of improved antennas. They operate in the VHF range (around 151MHz).
MURS has the following features/restrictions:
- No license needed
- Longer distance than FRS in suburban and rural areas due to waves bending around hills
- Not as long range as CB in suburban and rural areas (CB allows between 4 and 12 watts.)
- Less effective in urban/apartments areas, due to wavelength effect around concrete.
- Products are not as available as FRS. Expect to shop online and have fewer choices.
- 2 watts maximum output (PEP)
- FM modulation
- Five defined channels
- Optional antennas can be used; however, they cannot be over 60 feet above ground.
- Optional antennas can be about two feet long or more on the radio (better range with larger antennas).
- Coax can be used to connect to permanent or larger antennas.
- No repeaters allowed
- FM Modulation
- Has PL codes (Privacy codes), but these only restrict what you can hear, not what everyone else can hear.
FRS – (UHF) Family Radio Services
FRS radios are two way, low power (up to 2 watts on some channels), “walkie-talkies”. The antennas are fixed and cannot be extended legally. They operate in the UHF range (around 400MHz).
FRS has the following features/restrictions:
- No license needed
- Works better in urban environments than MURS and CB (higher frequency penetrates concrete better than lower frequencies, in general).
- Less effective in suburban and rural areas. (Higher frequencies do not bend around hills as well as lower frequencies.)
- Recent 2017 FCC changes have expanded the number of channels allowed to FRS; however, since these rules were just passed, your radio may not allow for the extended channels or the increase in wattage. (See http://wiki.radioreference.com/index.php/FRS/GMRS_combined_channel_chart for new frequency and wattage rules.)
- FRS has something referred to as PL or “privacy channels”. These privacy channels restrict what you can hear and not who you can send to or hear you.
- Output power is restricted by the FCC to 2 watts on some channels, and 0.5 watts on others. Anywhere between 0.5 to 2 watts is very low power for a portable two-way radio.
- The UHF frequency range limits this to line of sight. Do not believe marketing when it comes to outrageous distances. You can communicate beyond about 3.5 miles, but you have to have both locations well above sea level. Even then the low wattage will cause issues when trying to hear the other person.
- FRS equipment is restricted to a fixed antenna. You cannot legally swap out the installed antenna with one that is more efficient.
- Shares some frequencies with GMRS
- FM Modulation
- No repeaters allowed
- CERT uses FRS radios. CERT is an organization of volunteer local responders, often focused on search and rescue. Having the ability to operate on these frequencies may help guide assistance where it is most needed.
- Low cost, commonly available at mega-stores
Recommendations and Comments on FRS
Although the wattage is low and there are antenna restrictions, having a few FRS radios has the specific advantage of communicating with CERT teams and with neighbors. The low cost of ownership also allows these radios to be excellent hand out radios for neighborhood communications in an emergency.
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