On the 2-Meter Band, most of the US uses a 0.02 MHz frequency separation on the 145.110-145.490 MHz repeaters, but uses 0.015 MHz frequency separation on the 146.610 through 147.390 MHz frequency repeaters.

In the western US and Michigan and parts of Alabama, Washington, Oregon, Idaho, Montana, Utah, Arizona, New Mexico, Texas, Hawai, and parts of Nevada use 0.02 on all frequencies. While most of California uses the "Eastern" 0.015 pattern, the southern section and southern Nevada use 0.015 inverted -- output and input reversed on 146 and 147. The pattern for Alaska and the southern tip of Nevada is different, still -- a 0.06.

If you travel a lot, using memory slots on your mobile or HT for these frequencies saves you having to look up the frequencies in a repeater directory, such as that from ARRL. You may need to check PL/CTCSS tones (either in the directory or by scanning for them), but the frequency pair is all set.

If you reprogram to the "West" set, you would use 59 slots. [But if you leave 1 "East" when you reprogram 2 "West" for those 3 frequencies between the \ and / signs, you still tie up 73 slots.

"West" contains 25 frequencies not common to the "East" set -- so an "East"-"West" set would be 99 slots.

Programming only the "AK/sNV" pattern would use 24 memory slots, 11 of which are also common to both "East" and "West." Four (4) are not common to either "East" or "West." Nine (9) are not common to "West."

East = 73
West = 59 | E+W = 98
AK/sNV = 24 | W+AKsnV = 33 | E+AKsNV = 77 | E+W+AKsNV = 103

Often you will find two repeaters using the same frequency pairs, separated by less than 100 miles. In those, and in other good "line-of-sight" locations, you must transmit a CTCSS^TM (PL) tone to "open" access to one or the other or both repeaters. Once you have found an active repeater, check a repeater listing (such as The ARRL Repeater Directory) to see if there is a tone set. Or, if your radio is capable, scan for the tone.

It's not a bad idea to look through your repeater directory for frequencies along your route and double check against this chart. Repeater frequencies are coordinated locally. You may find a repeater whose input frequency varies from the [-]/[+] 0.600 "plan" because of preexisting conditions or because of interference with other services or repeaters. For example, the inverted pattern in California and Nevada could "fool" your radio's automatic settings.