A long while back Norm asked about FRS radio channel - clarity and signal strength. I've done some further research and have found out that many FRS radios advertised as having a 14-mile range are built as follows:

Quiet codes (the second number the 21 in a radio set to 7-21) also known as subchannels 1-38 are Continuous Tone Control Squelch (CTCSS) and 39-99 are Digital Coded Squelch (DCS).

According to Wikipedia:

CTCSS (Continuous Tone-Coded Squelch System) continuously superimposes any one of about 50 low-pitch audio tones on the transmitted signal, ranging from 67 to 254 Hz. CTCSS is often called PL tone (for Private Line, a trademark of Motorola), or simply tone squelch. General Electric's implementation of CTCSS is called Channel Guard (or CG). There are many other company-specific names used by radio vendors to describe compatible options. Any CTCSS system that has compatible tones is interchangeable. Old and new radios with CTCSS and radios across manufacturers are compatible.

DCS (Digital-Coded Squelch) superimposes a continuous stream of FSK digital data, at about 131 baud, on the transmitted signal. In the same way that a single CTCSS tone would be used on an entire group of radios, the same DCS code is used in a group of radios. DCS is also referred to as DPL tone (for Digital Private Line, another trademark of Motorola), and likewise, GE's implementation of DCS is referred to a Digital Channel Guard (or DCG). DCS is also called DCTS (Digital-Coded Tone Squelch) by Icom. Radios with DCS options are generally compatible provided the radio's encoder-decoder will use the same code as radios in the existing system. Be aware that the same 23-bit DCS word can, for example, produce three different valid DCS codes.

Thus, DCS Quiet Codes 39-99 should have the least interference since there is much more limited access to the Digital Data Signal.

On a 14 mile radio FRS channels 8-14 have a range of up to 5 miles. GMRS channels 1-7 and 15-22 have a range of up to 14 miles.

Based on this data it would appear the the best signal would be on channels 1-7 or 15-22 with a quiet code of 39-99. To implement the radio quiet code we now use would have to be changed. I suggest you give it a try and see if radio communication reception improves.

 

Trico,

Great information. Thanks for all the work. We can now work out choosing a stronger channel for the lead Mini & the caboose and perhaps have another channel set for "chatter" for the entire group. This would allow for "important" clear communications between the lead Mini and others, including caboose, without a lot of "chatter" and garbled interference during "critical" times of a run.

 

If the group sets radios to channel 7 and turns the quiet codes off altogether, the group members can chat among themselves on Channel 7. although clarity will suffer a bit. The group on 7 with no quiet codes can hear anyone on 7 irrespective of the quiet codes others on 7 may use. However, only those on a designated quiet code can communicate with each other. Consequently, one radio set to identical quiet codes between front and caboose would solve the problem and allow everyone to listen in. Of course, front and caboose would need a second radio set only to channel 7 without quiet codes to converse directly with other group members.

Me thinks I now know too much about this stuff!!!!