Part of our Emergency Communications and Preparedness guide.
Most preparedness comms plans I see start and end with a repeater. Program the local machine into a handheld, check into the weekly net, done. I get it. A repeater on a mountaintop makes a 5 watt handheld feel like a 50 mile radio. But that range is borrowed. Take the repeater away and most of those plans shrink to the size of a neighborhood.
My position: for regional SHTF communications, an HF NVIS capability is every bit as important as your repeater access, and in a real grid-down event it is probably more important. Not instead of VHF/UHF. Underneath it.
The Repeater Is Doing the Heavy Lifting
When you talk through a repeater, the repeater does almost all the work. It sits high, it has a better antenna than you, it runs more power, and it can see over terrain you can’t. Your handheld only has to reach the hill. The repeater handles the rest.
That also means everything depends on the hill: site power, backup batteries, links to other repeaters, and the road the trustee drives up to fix it. I walked through those failure points in When the Repeater Goes Silent, so I won’t rehash them here. The short version: a repeater is a single point of failure, and in a wide-area event it fails right alongside everything else.
Without the Repeater, You’re Back to Line of Sight
VHF and UHF travel in more or less straight lines. They don’t bend over a ridge, and outside of rare band openings you can’t plan around, they don’t come back down from the sky. Simplex range comes down to how far your antennas can see each other.
- Handheld to handheld: a few miles. At head height the radio horizon is only about 3 miles, so two handhelds on perfectly flat ground top out around 6 or 7 miles in theory, and usually less.
- Mobile to mobile: roughly 10 to 20 miles with good antennas and clear terrain.
- Base to base: farther with antennas up high, but now you’re relying on towers and masts again.
Then add whatever sits in between. A hill or mountain between you and the other station can kill the path outright. Buildings, block walls, and steel structures absorb and reflect the signal, so a city simplex contact that works on paper often doesn’t work in practice. Trees and foliage eat into UHF too. Sometimes you can find the one spot where a signal bounces in, but you can’t build a plan around finding that spot under stress.
What That Looks Like From Maricopa
I live in Maricopa, south of the Phoenix metro. Between me and most of the Valley sit South Mountain and the Sierra Estrella. Through a repeater, that terrain doesn’t matter, because the repeater is on top of it. On simplex, it’s a wall. A friend in north Phoenix might as well be in another state if all I have is a handheld and the repeater is dark.
Here’s the irony. The high ground that blocks your simplex signal is exactly where the repeaters live. When that high ground loses power, you lose the repeater and you’re stuck on the wrong side of the mountain at the same time.
Where HF NVIS Fills the Gap
NVIS sends an HF signal nearly straight up and lets the ionosphere drop it back down over a circle a few hundred miles across. The signal arrives from overhead, so the mountain between me and north Phoenix stops mattering. There’s no tower, no site power, and no link. Each station needs a radio, a battery, and a low wire.
From my station, that circle covers nearly all of Arizona. A single mountaintop repeater covers a few dozen miles. I covered the bands, antennas, and modes in detail in What Is an HF NVIS Regional Net?, so here I want to focus on how the two systems work together.
How I’d Layer VHF/UHF and HF NVIS When It Hits the Fan
Here’s the scenario I plan around. Pick your own disaster (monsoon damage, a grid failure, wildfire), the shape is the same.
Hour zero: the power goes out across the region. Repeaters with battery backup are still up, and they’re busy. This is VHF/UHF’s best moment. Family checks in, the club net spins up, and everybody hears everybody. Use it while you have it, and keep transmissions short so the repeater’s batteries last longer.
Hour six, maybe hour twenty-four: the repeater goes quiet. The batteries ran down, a link died, or something on the site failed. This is where most plans end. In mine, everyone already knows the fallback: a pre-agreed simplex frequency (not 146.520, where everyone else will pile on). Inside my neighborhood and between our vehicles, simplex still works fine. That covers the people within a few miles of me.
The gap: someone across the Valley. Now I need to reach a friend in north Phoenix, a group in Tucson, or just find out what’s happening beyond what I can see. Simplex won’t get over South Mountain. This is the HF NVIS job. At a scheduled time, I’m on a known frequency with SSB, 40 meters during the day and 80 meters after dark. When voice gets rough, we drop to JS8Call, which decodes signals that voice can’t carry.
The bridge: one station runs both. The station with both radios becomes the relay. Information comes in over HF NVIS and goes back out over VHF/UHF simplex to everyone nearby who only has a handheld. A station on the far side of the region does the same at their end. That gives you two local VHF/UHF clusters connected by an HF link that depends on nothing but the stations themselves.
Beyond the region: going long. If the whole region is dark, everyone you reach on NVIS may know as little as you do. The same HF station can switch to DX and reach people outside the event who still have power and news. I walk through how to poll other states and continents, and what to ask them, in Why HF Radio Matters Most When the Grid Goes Down.
Who Gets What Radio
- Everyone in the family or group: a VHF/UHF handheld, all programmed the same, with the repeater, the simplex fallback, and a couple of alternates. Simple, light, and good for the bulk of traffic, which is local.
- Every vehicle: a mobile VHF/UHF radio. More power and a better antenna stretch simplex range. In my Jeep that’s an AnyTone AT-D578UV III Plus.
- At least one HF station: on battery, with a low horizontal wire or an EFHW strung low and level. Mine is my FTX-1 go-box with the Optima SPA-1 amplifier inside, which gives me a full 100 watts for SSB wherever I set it up. It also covers VHF and UHF, so the same box can work the HF NVIS net and talk to the local handhelds on simplex. That makes it a natural fit for the bridge station.
- At least one General class operator: HF voice on 40 and 80 meters requires a General license or higher. If that’s your gap, start with Getting Licensed.
Comm Windows Make It Work
HF NVIS isn’t an always-on channel like a repeater. People have to be listening at the same time. Set fixed check-in times (top of the hour, or every three hours to save batteries), a primary and alternate frequency on each band, and the order to try them in. Write it down and put a copy in every kit.
That’s the core of a PACE communications plan: the repeater as primary, simplex as alternate, HF NVIS voice as contingency, and low-power HF digital as emergency.
Practice Before You Need It
None of this works the first time under stress. Run the repeater net. Then run a simplex test from home and find out where your neighborhood coverage really ends. Then run an NVIS net and map who hears whom. If your group only ever practices on the repeater, you’ve only tested the layer most likely to fail first.
Keep the repeater. Use it every day. Just don’t confuse it with a plan.