Old thread, but I thought I'd add this for those that find the thread looking for a cheap comms option.
Nextel handheld radios ~ preferred models are #Motorola i355 and i570 for durability, function and privacy.
These old Nextel phones work WITHOUT a service plan. Range exceeds what your going to get out of the typical box store 2 way radio systems at considerable savings. They can be setup so that you can make "calls" to an individual radio or you can broadcast to your "group". Battling for an available frequency is not an issue as seen in CB, GMRS, FRS.
How to program for off network use
https://www.youtube.com/watch?v=K3ipEX-87Hg
With it's own antenna 2 miles is the range, but it can be increased range of near 15 miles line of sight via 6dB gain
https://www.youtube.com/watch?v=kqxAQUH3dmQ
Ebay buy it now for $15
Motorola I355 | eBay
NOTE: You will also need to purchase a new sim card for each radio, also available on Ebay.
These radios can cover a large area very securely using the PRIVATE CALL feature.
Private Intercom allows for (the most part) privacy that can only be overridden if someone duplicates one radio's "LINE 1" information. Otherwise it is a private function that restricts even the Receive All setting on other radios from over-hearing the conversation.
To reach a specific radio the radio must be set for YOUR CHANNEL and YOUR CODE or YOUR CHANNEL and PVT only. You will be able complete the 2way communication if you know the other party's "LINE 1" information. This feature can be used to (usually) reach only that ONE individual device you are attempting to reach using the following setup information:
Turn i355 radio on and go to menu and select "My Info". Then choose EDIT and select the LINE 1 field. Enter a digit string of between 1-20 digits long that you want the current radio to be known as. After this information is entered then Reboot the radio (power down and power back up). (SEE NOTE #3)
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To test:
From another radio, go into Mototalk/Directalk mode. Using the keypad enter the number that you input into the other radio as LINE 1 and the then "call" that original radio by pressing the PTT key.
If it doesn't work go back and check your digit string. Also make sure that you HAVE REBOOTED before attempting to reach the far end. You should also make sure that your CHANNEL and CODE or CHANNEL and PVT are set up on that device. The CHANNEL and CODE must be the same on both radios. SEE NOTE #4 if one radio does not reach the other.
NOTE #1: If 2 radios have the same LINE 1 information the calling radio will be able to reach both DUPLICATE radios. When ONE of the DUPLICATE radios responds the other DUPLICATE radio will not hear what the responding duplicate radio is transmitting.
NOTE #2: Even if ANY radio is set for the same CHANNEL and RECEIVE ALL it WILL NOT HEAR any private communications between 2 radios that are using the LINE 1 information as a means of communication.
NOTE #3: The Digit string should be the same length for all radios in the group. By using a (standard) 10 Digit Phone number style length (North America) as an ID it will make it less likely to have duplicate strings (members) if multiple groups of radios join each other on the same CHANNEL and CODE for some period of time and still wish to use the private call function. It is recommended to use a 10 digit string (or greater) that may include a combination of the typical LOCAL AREA CODE and first few digits of the LOCAL POSTAL CODE with the last 4 digits being a variable for radio by radio. This will make it very unlikely that if 2 groups joined together on the same CHANNEL and CODE for a short time that there would be any conflicts. Conflicts and Duplicates will result in the loss of privacy. (Any numbering scheme will work as long as consistency is used throughout group of radios.
NOTE #4: With most (if not all) Firmware or SIM cards your must have the LINE 1 information populated in YOUR radio before attempting to reach another radio using the LINE 1 information as a means to contact. Do not forget to REBOOT your radio if you have just added this information.
NOTE #5: You can set-up your contact list for frequently contacted radios using this manner of communications and it will speed up the process when used.
NOTE #6: This Private or Intercom calling will not work if you have started DirecTalk or MotoTalk using the 911/112 SEND/END method bypasses the missing SIM card and the Private Comms discussed above requires the use of a iDen SIM card
This is the list of radios that Sprint lists as compatible with Direct Talk:
i325
i335
i355
i365
ic502
i570
i580
ic602
i615
i850
i855
i880
ic902
Channel/Code feature - Is someone else listening?
How to know and change your operation to avoid eavesdroppers.
A few years ago FRS/GMRS radios were marketed as having "hundreds of channels". They did this because they were taking the actual channels that could be used on the radio (usually 7 FRS and 15 GMRS) and use the privacy codes, sometimes just a few and now as many as 143) as a multiplier. In reality the use the privacy codes does not "add" (or multiply the) channels on an analog radio.
On most non-digital radios (FRS/GMRS/HAM/Commercial/Government/others) the privacy codes are usually known as either PL (Private Line), CTCSS (Continuous Tone-Coded Squelch System), DCS (Digital Selective Calling) or DPL (Digital Private Line).
PL and CTCSS are related as the same feature and DCS and DPL are related as the same feature. They just have different names. The difference between PL/CTCSS and DCS/DPL is former is analog encoding the latter is digital encoding. Yes, you can put digital privacy codes on an analog radio transmission. Many current FRS/GMRS radios can use either PL or DCS as a potential selection for privacy.
There are other names and types but they all basically do the same thing. When the radio is transmitting not only is it sending the spoken audio from the microphone but it is also carries with it what is known as a sub-audible tone or a digital code. It is called a sub-audible because the receiver can "hear" it but the tone or code but it does not make it out to the audio section of the radio and therefore the user does not hear the tone or code. It is only used as a means to control or to restrict the radio from transmitting or the receiving audio unless the transmission includes the matching tone or code.
On most FRS/GMRS radios the use of privacy codes for transmitting purposes acts as a means to restrict other radios on the same channel (frequency) that use a different privacy code, from interfering while the channel (frequency) is in use.
In the case of receiving transmissions, the privacy code operates in the same manner. When a FRS/GMRS radio hears activity on it's programmed channel but the privacy code does not match it will restrict the reception of a transmission through to the speaker/headset. Once the matching privacy code is heard any transmissions that uses that same code will be heard.
Some radios can be set to transmit the privacy code but not listen for a specific code. This allows for more freedom to be aware of the condition of the channel when other users are using other privacy codes.
Privacy code use on FRS/GMRS only allows for pseudo-privacy because a radio that does not use, have or enforce the use of privacy codes can hear and transmit no matter what the other radios are using for a privacy code so long as the channel (frequency) is the same.
When there are enough radios on the same channel and they are using different privacy codes it may become impossible to use your channel because your radio is set for a certain code and it is only listening for transmissions that code. The other radios are set up the same way for their own codes and enough traffic could make that particular channel unusable as no one may be able to transmit or receive in a reliable manner.
Another issue with the FRS/GMRS privacy codes is when a user chooses not to use a privacy code or the radio does not have the capability to use a privacy code. If this is the case, every time any radio that does not have the privacy code or does not enforce its use, the radio does not check to see if the channel (frequency) is in use and effectively takes over the channel when ever it transmits. Those radios are using the privacy codes at this time do not hear that the channel is being transmitted on because the transmission is not carrying with it the sub-audible privacy code. This too will make a channel unusable. Often those that use FRS/GMRS radios in a busy venue will turn off the privacy codes so they can be heard but end up "stomping" on the more polite users. When this happens he who has the most power or better antenna usually wins.
Now keep all that in mind as we discuss the iDen radios
The iDen radios have 150 communication paths (not including Private mode) to minimize interference. This is done by using 10 channels and 15 codes per channel or 10 x 15 =150.
The codes on an iDen radio can be used as a multiplier unlike it's FRS/GMRS counterpart. The codes on the iDens are more like a sub-channel rather than the pseudo-privacy codes on the FRS/GMRS radios.
On the iDen radios one could set up a pair of radios on Channel 10/Code 2 and not interfere with the others that would setup their radios up on Channel 10/Code 3.
In the FRS/GMRS environment any use on one channel could prohibit others from using it. In FRS/GMRS world the 10/2 group would have to standby and wait for channel 10 to clear as it would appear busy until the 10/3 group was done (and vice versa). In the iDen radios there is no indication of use on channel 10 to those not on the same code because there is not interference between the codes.
When setting up an iDen radio as stated before it can be setup using any one of 10 Channels and Codes 1-15. There are 2 other code settings as well. One selection is "Receive All" and the other is "PVT Only".
The "Receive All" feature on iDen radios allows the radio to monitor all the traffic on one particular channel no matter what code is used. This somewhat mirrors the functionality of the FRS/GMRS radios being setup without using a privacy code. One of the differences between the iDen radios and the FRS/GMRS is when the iDen radio is set to "Receive All" the iDen radio can not transmit on any channel or code until the radio is set for a channel and a specific code. Its FRS/GMRS counter part CAN transmit to any radio using any code or no code.
Most FRS/GMRS radios use a simple protocol to maintain a reasonable level of communications. These radios will simply transmit from one radio to any other radio. The FRS/GMRS radios usually will not indicate if they were successful in making a contact as they tend to just spray this signal out on one channel that may or may not include a privacy code and if something gets it then it's user should return the transmission on the same channel and code. With few exceptions there is no way to know if there was actually another radio within listening distance.
The iDen radios use a unique protocol when it transmits seeking a recipient. The radio initiating the communications will send a signal out and wait for a short period for any receiving station on the same Channel and code OR a station set up for the same Channel and set for "Receive All" to acknowledge. Either of these types of setups will automatically acknowledge to the initiating radio that it was in range of and was able to clearly "hear" the transmission. If the initiating radio did not get an acknowledgement it would display "User Not Available"
Here is the indicator that should spark your COMSEC interests:
As stated before, any iDen Radio that is set up with the same channel and the same code as the initiating radio will return a response and then the transmitting radio will display "Transmit" and the Receiving radio should show as expected "Receive" and then the reverse would be true when the receiving station transmits to the formerly transmitting station. It sounds very elementary except that a radio setup on the same channel as the transmitter and the code "Receive All" looks to the originating station like a radio that it can be in a two-way conversation with but the "Receive All" station can only listen.
If someone was fishing for a set of iDen radios that were communicating with each other they would only need one iDen radio and then periodically monitor each channel for a few seconds or minutes at a time using the code "Receive All". The fisherman would would need only to listen to the radio to find someone transmitting and then the perceived security for having these radios may soon fade away.
Another more expensive an elaborate way to listen in as the fisherman, would be to have 10 radios with each radio on one each of the 10 Channels and then each one set up "Receive All". The fisherman, providing he was in range would immediately hear any of those transmissions on any channel with any code.
The security minded iDen users would periodically have all radios in his group shut down and when he knew that there was no radio on their channel and code they would transmit every so often. If no one is on the channel the radio will return the message "User Not Available" If they do not see that message they have either forgot a radio or there is a fisherman in the area.
The Most Secure ways to use the iDen radios:
Only communicate on an "All Call" Channel/Code manner during urgent situations. Otherwise program each radio in your group with a private number. So long as that number is long enough and/or complex enough not to be guessed, it would be very unlikely that a fisherman could hear anything. To make it harder for the fisherman, he would not only have to guess or glean the private numbers, he would also have to know the channel that is being used for the numbers.
Here is the caveat to the privacy method of managing your iDen radio security:
If the fisherman knows the private number of someone they wish to monitor all the radio traffic received by that radio, the fisherman would only need to duplicate the private number of that radio. Whenever a transmission was sent to the legitimate operator, the fisherman would hear the same transmission.
But what is a fault is also a feature...
If you don't feel that you need the private calling feature to reach each radio individually then you can program the same long and/or complex number in the Private Line of multiple radios. You would then use that number to reach each other (at this time I do not know if there is a limit). If all the radios are setup the same, then all radios will receive the same traffic as well as transmit to the same number and it can not be heard by the fisherman's radio that would be setup using the correct channel and "Receive All". The Code on these sets should be set to "PVT Only" to avoid accidental All Call broadcasts on the Same Channel/Same Code Comms. Physical security of these radios become paramount when using Private Calling to communicate at any level. If the numbers get out you have lost all security if there is a fisherman in the area gathering intel.
Here is a list of how to program the iDen radios from least secure method to most secure with notes as to the benefits and concerns:
All Radios on the Same Channel/Same Code | useful for communicating within a group and everyone in the group hearing it | A Fisherman can have a radio set up to listen to same channel and "Receive All" code and then hear any traffic on any code within that channel.
All Radios using individual Private Numbers | useful for person to person communication that generally can not be overheard | Any radio setup with the same Private line as anyone in the group will intercept those private transmissions.
All Radios using the same Private Number as well as programmed for Same Channel and "PVT Only" | Gives the same benefits of Same Channel/Same Code use as for All Call without any concern of a Fisherman listening using the "Receive All" code | Disclosure of this Private Line number can cause a complete loss of communications security
NOTE:
Except for someone having an iDen radio (which is very rare at this time) all of the communications security failures are fairly unlikely. Because generally most COMSEC threats will come from a scanning receiver (that can not usually intercept iDen Comms) it will be virtually impossible to intercept the Comms traffic. The other alternative to having an iDen radio as a means of intercepting radio traffic would necessitate one the acquisition of a very expensive ($15K-$21K) Communications Analyzer. These analyzers are already rare and will become more rare as the iDen is phased out. (The planned phase out will not cause any known issues with the Direct Talk feature or security)
Read more at
http://www.survivalistboards.com/showthread.php?t=193571&page=2#E4pQ00c7cOgG5BSd.99
For under a hundred bucks you can have your 4 favorite neighbors able to communicate!