The basic problem with using HF radio is that you need to know most of the things required for a ham license to operate one. Modern HF radios have displays, scanners, lots of features, and are moderately complicated to operate. Even hooking up an antenna requires some understanding of what antennas really do.
Here's a typical modern portable ham radio.[1] (Not a recommendation, just an example) This one does both HF and VHF, so you can reach both SHARES and locals. Here are some simple wire antenna kits.[2] If you have both of those items, and some kind of power (a car battery), you can contact various US emergency services, radio hams, preppers, and whatnot, even if infrastructure is down for hundreds of miles around.
A small solar panel to charge the thing would be a good idea. All this is probably about US$1500.
Any isolated town should have something like that, and some people who know how to use it.
Town halls, volunteer fire departments, sheriff's offices, etc. are good locations to keep it.
Preppers seem to be more into VHF handhelds such as the Baofeng UV-5R. That's about US$80.
Less range, can't reach SHARES, but can reach a few miles, depending on terrain.
Useful if you're two miles from the main road.
Here's a prepper view.[3] He uses a Slinky as an antenna.
Once you have the ability to communicate at all, the problem is finding someone useful to talk to in an emergency. There's no addressing, just frequencies. On HF there's so much range that most of the people you can reach are not in a position to do much. The whole point of SHARES is that there are a few frequencies where someone is regularly listening. During a disaster, they're probably dealing with bigger problems than yours, so calling up Homeland Security HQ as an individual may not be helpful for anything not immediately life-threatening.
If you're near a coast, you can usually reach the Coast Guard on a marine VHF channel. They're a first responder set up to take radio calls.[4] If the emergency requires a boat, call them. Marine Channel 16 VHF-FM (156.8 MHz). The Coast Guard gets involved with major floods, they maintain good communications with other emergency services, and they know almost everybody with a boat.
In the simplest analogy, it's just the TV rabbit ears with two wires in opposite directions, except much longer wires, because the frequencies are lower and therefore the wavelength is larger. Those classic rabbit ears are effectively a dipole antenna, which is basically: "stretch a wire out in a line so it's half the wavelength of the frequency you want to receive or transmit on, cut it in half, and send the signal from the middle, out both ends of the cut wire".
Picking that length of wire results in the lowest impedance (kind of analogous to friction) at the radio for pushing signal out to the antenna, but various lengths work with more or less efficiency, and you don't have to send the signal from the middle either if you have appropriate inductors and capacitors to adjust the impedance (it's just the simplest way).
As with most things on the internet these days, it seems the best content is in the form of YouTube videos, so amusingly, this is the best written information I came across after some quick searching:
A dipole is a very simple antenna, and pretty efficient. There are other shorter options that have worse performance too, but perhaps more suitable for an adhoc tree deployment. (random wire, EFHW)
(I know you know this, but just adding in. Ham is fun! I like doing park & camping deployments)
Having been in the WNC hurricane area, I have a newfound interest in this stuff.