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Communications

This material used by permission, thank you Dr. Who...


Communications

 

Radio/communications is in military terms a force multiplier, i.e. it enables people to communicate over greater distances that shouting or relaying messages and makes important information easy to obtain and an immediate response. In the Patriots novel one of the retreat experts said “If you don’t have comms (communication) you don’t have Jack”.

SOME BASICS:

Prior to or immediately after a crisis you will want to have AM/FM radio and preferably a short wave receiver with SSB (single sideband) to gather general news from your area and abroad. AM & FM for local and Short Wave for worldwide. Here is a link to a good radio receiver:

http://www.amazon.com/Traveler-G3-Shortwave-Single-Side-Synchronous/dp/B001QTXKEW The optional antenna in this link is a good idea & will increase reception greatly. This is only a receiver and you can’t transmit with it. Most likely there is no real need to have to communicate to people thousands of miles away so an HF (High Frequency) HAM rig is not necessary at this phase. Local communications with members of our group will be extremely important.

There are basically two types of radio’s that we can use with local comms (communication). Either a handheld (walkie talkie type) radio usually referred to as an HT (Handie-Talkie) or a mobile radio that can be used in a car or at home. An HT radio is limited to low wattage, usually 5 watts maximum. They also come with a small antenna since it’s hand held. A mobile radio can be used in the car & also removed so that it can be used in the home. You just have to disconnect the antenna & power cables along with disconnecting the mounting bracket.

Local comms are based on line of site. This is a part of the VHF (Very High Frequency) and higher frequencies of the RF spectrum where the wavelength is too short to pass over structures and hills. The transmitter and receiver antennas must be in line of site. Some radio’s will tell you that their range is up to 36 miles with an HT. That would be so under optimum conditions, like being on top of a high mountain. Typical will be 1 to 3 miles. So how can we increase the range of these HT’s? There are a few ways to do this.

  1. Increasing the antenna size
  2. Adding a counter poise
  3. Using an external antenna
  4. Using a repeater
  5. Other

 

Increasing the antenna size

When purchasing an HT, make sure that there is an option to change the antenna. Using the standard antenna that comes with an HT is not a good idea. If you used the 5 watt power setting (the max on an HT), the power feed into the factory antenna will effectively be only 1 watt output when it leaves the antenna. So we have to change the antenna. There are many types of connections that the HT has with the antenna. The following connection types are the most popular: SMA connector & BNC connector. The SMA connector is most common. It is small & very fragile. Be extremely careful because if it breaks, the HT can be rendered unusable. When you look at replacement antenna’s look at the “gain” and wavelength. The bigger the gain the better the antenna. The larger the wavelength, the better the antenna. A 3db gain is better than a 2 db gain. A 5/8 wavelength is better than a 1/4 wavelength. 

Adding a Counter poise

A simple, inexpensive and effective method to improve an HT antenna is by adding an external counterpoise or "tiger tail" thereby adding the other half of the antenna. You can easily build one from a quarter-wave piece, (about 19.5" on 2m, 11.5" for 220 and 6.5" for 440), of stranded insulated wire, crimped and soldered to a battery clip or use a small spring tension clip that will fit the antenna connector with the wire attached to it. Use a clip or other connection that fits tightly but can be removed if needed. It must make both a good mechanical and electrical connection. You just built a directional antenna and did not know it. In marginal conditions, extending the counterpoise horizontally and pointing your hand to steer the radiation pattern where you need it, produces a dramatically stronger signal than letting it "droop" towards the ground. Experiment with the angle of the counterpoise to get the best results. In effect, you are creating a form of "V" type center fed vertical dipole with a bit of gain compared to just the factory installed antenna.

Adding an external antenna

You can purchase or make a pocket roll up J-pole antenna. When out in the field, you can take it out of your pocket & throw it up over a tree branch & hook it up to your antenna output. It will increase your output by increasing your antenna size & height. 

Using a repeater

Most Ham radio clubs have a repeater system. A repeater is a two-way radio system that receives on one frequency, then re-transmits what it hears on another frequency; at exactly the same time. Your mobile or HT has a limited range due to it's antenna height with respect to the radio horizon and rf attenuating surroundings.  Repeater systems are used to "transfer" your transmitted and received signals to much higher elevations electronically using large, very efficient antennas located on top of hills or towers. A repeater "gets out" your signal and receives the station you are talking to with a far greater range and coverage area. You take advantage of the repeater's higher elevation and power to increase your effective transmitting and receiving coverage versus your mobile or HT.

Other

When you're using a HT radio, you'll get the best range if you hold the radio vertically, not tilted over your shoulder. If you have the option, move outside or towards a window. Don't stand behind or near anything large and metal that might absorb the signal. In most cases, if you move around to where you hear the best, that's also where you'll talk the best. If you use a speaker mike, you can even hold the radio up over your head to get a bit more height. Keep in mind, also, that when the portable is on your belt your body is soaking up something like 80% of the signal. So take the radio off your belt and stick it up in the air if you're in a weak signal area. If you're in a fringe area in your car, wait to transmit until you're on the crest of a hill. Avoid transmitting from under bridges, in tunnels, alleys or behind high buildings.

Mobile radios

These radio’s are larger in size and more powerful than an HT. They typically will have 50 watts or more. They can be installed in your car, removed and also used in your home. The antenna & power cables need to be removed before it can be moved. A 12 volt power supply will be needed when you use it in the house ($75.00). These are the type of radio that can be used to communicate between members of this group. These radio’s cost between $130.00 and up. A magnetic mount antenna for the car is approximately $35.00. An antenna for the home would cost between $35.00 to $100.00 and would need some type of mount and or mast connected to the house. It would also need an antenna cable (coax). 25 feet of preassembled coax cable with connectors on would cost around $15.00. The range on this type of set up in the house would greatly depend upon the local terrain. Using a repeater you should be able to get good coverage over most of the Island. Using my local repeater I have talked to mobiles going over the Tappan zee bridge from Northport.

http://www.universal-radio.com/catalog/fm_txvrs/1900.html   $130.00

Typical mobile radio

 

 

 

 

 

 

http://www.universal-radio.com/catalog/hamantm/3243.html Car antenna with magnetic mount. $35.00

 

 

 

 

 


HT radio:

 

http://www.amazon.com/BaoFeng-UV-5R-136-174-400-480-Dual-Band/dp/B007H4VT7A

Very cheap HT $43.00 on Amazon, cheaper on ebay. A little harder than most HT’s to program but extremely cheap.

 

 

 

HT with counterpoise

 

 

Remember that you do need a license to transmit on Ham radios.

BUT if you transmit you could be giving your location away to radio direction finding methods. People can use radio direction finding against you  EASILY if they know what they are doing- look up HAM radio DF http://www.homingin.com/

So knowing that you could be tracked if you transmit, DO NOT TRANSMIT from your
  base camp unless absolutely necessary.

Again for OPSEC (operational security) do not transmit form your base camp. It is better to listen rather than to talk. If you are using encryption or not it is best to use code, grids, or predefined words with meanings only to you. In WW2 the only codes that were not broken by the other sides was the wind talkers, the native Indian dialect that was only in the USA with a small tribe.  Remember its better to be the hunter rather than the hunted.

 

HT with counterpoise

 

 

Remember that you do need a license to transmit on Ham radios.

BUT if you transmit you could be giving your location away to radio direction finding methods. People can use radio direction finding against you  EASILY if they know what they are doing- look up HAM radio DF http://www.homingin.com/

So knowing that you could be tracked if you transmit, DO NOT TRANSMIT from your
  base camp unless absolutely necessary.

Again for OPSEC (operational security) do not transmit form your base camp. It is better to listen rather than to talk. If you are using encryption or not it is best to use code, grids, or predefined words with meanings only to you. In WW2 the only codes that were not broken by the other sides was the wind talkers, the native Indian dialect that was only in the USA with a small tribe.  Remember its better to be the hunter rather than the hunted.




PART TWO

Longer Range Comms -

This is a follow up on my previous article on local comms. There will be times when you will want to communicate with a longer range.

  When a Ham radio operator uses the HF (High Frequency) bands, this is a part of the short wave spectrum of frequencies. It is below the VHF (Very High Freq.) we talked about with local Comms.

Contacts using these frequencies are usually very long range, Intercontinental (all over the world).  Radio waves are bounced off the ionosphere layer of the atmosphere and skipped many thousands of miles away.

There is a method called NVIS (Near Vertical Incidence Skywave) where you lower the antenna very close to the ground and direct the radio waves straight up so that when they bounce off the ionosphere they come back in a much closer range, usually between 30 to 400 miles.

The military uses this method all the time. Of course, they have their own part of the radio spectrum. These antennas are horizontal and are just wire, making them very cheap to make & setup.

This is a great way to communicate when there are a lot of mountains around (like upstate NY or PA) blocking line of sight.



Another NVIS setup. If the antenna was raised from 7 feet off the ground to 40 feet off the ground, the range would go from 30-400 miles to thousands of miles, keeping everything else the same.

 

So, one more expensive mobile ham rig that has HF & VHF can be used for local comms & NVIS in both the car & in a base (home) station.


Of course, both of the above radio’s can also be used for regular HF Comms- around the world. The NVIS antenna would just have to be raised up off the ground or have a second antenna with an antenna switch. You do need a bump up in Ham license to General Class to transmit on most HF frequencies. You do not need a license to purchase any of the equipment. There are also many Ham fests where used equipment is sold at a much cheaper amount. A Technicians license (entry level) is needed to transmit on VHF/UHF (local) frequencies. You are also required to identify yourself (give your call sign) every ten minutes while you transmit.


Tech Manuals sources:

 
 
 
 
This is the master list. Some good stuff, some not so good.

Getting started in Ham Radio, part 2 – wavelengths and watts and whatnot









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