Use of FRS / GMRS Radios in Backcountry
Posted: Thu Nov 30, 2006 8:54 pm
I am by no means on expert on this subject, but I've been hanging out with some radio experts and have changed how I use radios based on the knowledge my friends have imparted to me.
My main point is in regards to the use of "subchannels", eg channel 8 sub 2. "Sub" is short for "subaudible tone" (not "sub-channel") that's transmitted on your signal. Radios set to a specific "sub" (usually numbered 1 to 38 ) block out all incoming signals on the same CH except those using the same "sub." Radios set to "sub" 0 (no tone) will hear all signals (with any or no "sub") on the same CH.
People using the same channel but different SUB (other than 0) won't hear each other. Nice right? That's what you want, right? Well... if you're in a big box store, or Disneyland, or the county fair the SUB is nice because you won't hear everyone else on the same CH.
An important fact, though, is that you will be able to hear ONLY someone on the same CH and SUB.
So, let's say Mary, Dave and I are out in the woods and have our FRS or GMRS radios set to CH 9 sub 7. Then, let's say, I become separated from my group. I start radioing them, but they turned their radios off, or some such thing. Anyone on CH 9 sub 0 OR CH 9 sub 7 can hear me. So, I put out a distress call. If someone on CH9 sub 0 hear's me and tries to respond, I can not hear that caller... I can hear ONLY someone transmitting on CH 9 sub 7. With up to 38 subaudible tones per channel, the likelihood of someone else being on the same CH and sub is pretty small.
Subchannels provide for convenient private conversations in big public areas, but can be more harmful than good in remote areas if the radio is being used as a potential tool for safety.
I never knew this stuff, and always fell victim to the the "privacy channel" gimmick without understanding the ramifications of it.
Cliff notes:
If I have a radio is tuned to CH 9 sub 7:
Only those on [CH 9 sub 7] -OR- [CH 9 w/NO sub] will hear me.
I will hear ONLY others using CH 9 sub 7. I can not hear someone on CH 9 w/NO sub.
My main point is in regards to the use of "subchannels", eg channel 8 sub 2. "Sub" is short for "subaudible tone" (not "sub-channel") that's transmitted on your signal. Radios set to a specific "sub" (usually numbered 1 to 38 ) block out all incoming signals on the same CH except those using the same "sub." Radios set to "sub" 0 (no tone) will hear all signals (with any or no "sub") on the same CH.
People using the same channel but different SUB (other than 0) won't hear each other. Nice right? That's what you want, right? Well... if you're in a big box store, or Disneyland, or the county fair the SUB is nice because you won't hear everyone else on the same CH.
An important fact, though, is that you will be able to hear ONLY someone on the same CH and SUB.
So, let's say Mary, Dave and I are out in the woods and have our FRS or GMRS radios set to CH 9 sub 7. Then, let's say, I become separated from my group. I start radioing them, but they turned their radios off, or some such thing. Anyone on CH 9 sub 0 OR CH 9 sub 7 can hear me. So, I put out a distress call. If someone on CH9 sub 0 hear's me and tries to respond, I can not hear that caller... I can hear ONLY someone transmitting on CH 9 sub 7. With up to 38 subaudible tones per channel, the likelihood of someone else being on the same CH and sub is pretty small.
Subchannels provide for convenient private conversations in big public areas, but can be more harmful than good in remote areas if the radio is being used as a potential tool for safety.
I never knew this stuff, and always fell victim to the the "privacy channel" gimmick without understanding the ramifications of it.
Cliff notes:
If I have a radio is tuned to CH 9 sub 7:
Only those on [CH 9 sub 7] -OR- [CH 9 w/NO sub] will hear me.
I will hear ONLY others using CH 9 sub 7. I can not hear someone on CH 9 w/NO sub.