Calling Frequency Use
I pasted (and excerpted) the below from the ARRL website. Could someone please explain two things below, "Nat'l Calling Freq." and "Nat'l Simplex Calling Freq." What they're for, how they're used, and what's the difference between the two. Keep in mind I am brand new to this game and know nothing about either of them.
2 Meters (144-148 MHz)
144.00-144.05
EME (CW)
144.05-144.10
General CW and weak signals
144.10-144.20
EME and weak-signal SSB
144.200
National calling frequency
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146.40-146.58
Simplex
146.52
National Simplex Calling Frequency
146.61-146.97
Repeater outputs
147.00-147.39
Repeater outputs
147.42-147.57
Simplex
147.60-147.99
Repeater inputs
Calling Freq Demystified
There are two calling frequencies in the 2m band plan for the two primary modulation methods:
144.200/432.100 are intended for SSB Modulation.
146.520/446.000 are intended for FM Modulation.
As for how they are used, here a common (but not the only) use case:
Imagine you are on a road trip and out of range of W3VPR (sadness, I know!). But you don't necessarily want to find/hop on local repeaters of areas you are passing through, these frequencies can be used to chat with other hams on the road. I have used the 146.520 when travelling to Dayton. With a lot of other hams on the road, I was frequently in range of someone to talk to. Also handy for those speed trap reports!
That being said, you'll be surprised at the range difference you get in simplex versus from a repeater. UNlike the footprint of W3VPR which can stretch from southern PA to southern MD, I see ranges of maybe 10 miles on the flat areas (like Ohio), less in the built up areas or hills. You're not leveraging a 200' tower in simplex, so it's only as high as your vehicle's antenna.