Excerpted From The Source: http://www.northmainewoods.org/ (Navigate to Information Page on Menu)
If you are using a Garmin Astro or Garmin Alpha tracking system, be advised that the collars for these systems operate on the same MURS (Multi-Use Radio Service) frequencies used by logging trucks for monitoring road traffic.
These collars create audible interference on truck radios that are within range of a collar operating on the same MURS frequency (i.e. channel). The first four frequencies (channels 1-4) are used primarily for monitoring road traffic with each road system in the NMW region being assigned a specific MURS channel. MURS Channel 5 has been designated the channel for dog collars to operate on.
To determine which channel your dog collar is operating on, you will need to check your GPS receiver’s channel number (Alpha system) or Dog ID number (Astro system) that has been assigned to each collar:
ALPHA SYSTEM: The first number (followed by a Dash Number) indicates which MURS channel the dog collar is operating on. For example: 3-29 indicates MURS channel 3 as the channel being utilized, 1-18 indicates MURS channel 1, 2-7 is channel 2, etc.; therefore anyone using the Alpha system should have a 5 as the first number for each collar.
ASTRO SYSTEM: The Astro system assigns an ID number (0-49) as opposed to using a channel and subset number like the Alpha system, but the MURS frequency can be determined from this ID code by using the following chart:
ID Code 0-9 (151.820 Mhz) = MURS Channel 1
ID Code 10-19 (151.880 Mhz) = MURS Channel 2
ID Code 20-29 (151.940 Mhz) = MURS Channel 3
ID Code 30-39 (154.570 Mhz) = MURS Channel 4
ID Code 40-49 (154.600 Mhz) = MURS Channel 5
Collars that are not operating on the proper channel will need to be manually programmed to channel 5 (Alpha) or manually assigned a Dog ID number from 40 to 49 (Astro). Please consult your owner’s manual on how to manually program a collar or contact the NMW office (207-435-6213) for assistance.