In my experience, "sub-channels" (CTCSS squelch) is rarely used since it's difficult to set on the fly on many radios: it requires either re-programming a channel with the correct CTCSS frequency, or manually setting the Rx/Tx frequency and CTCSS frequency -- which can lead to errors, specially when trying to change channels in the thick of battle, and transmitting on channels you shouldn't be on.
Additionally, some radios (like Motorolla Sabres) have to be reprogrammed by computer and I think they don't even support CTCSS.
Quote:
Originally Posted by DustMagnet
However, I've heard that frequency assignments for CTCSS may not be identical across manufacturers.
|
What changes sometimes is the assigned "sub channel" number representing a given CTCSS tone frequency.
Here's a good example of it:
http://www.popularwireless.com/codetable.html
So to re-use Morb's orginal example, for some people sub-chan 21 would actually be 22 on their radios. So its important to be aware of your radio's specs.