Put the camera in the downstairs nursery and the parent unit upstairs on the same side of the house, close to the stair opening. One floor is not one wall: a wood-framed ceiling with drywall costs some signal, while a concrete slab with rebar or foil-faced insulation can cost most of it. DECT audio in the 1.9 GHz band survives that path better than 2.4 GHz video because it sends far less data and tolerates a damaged packet. If you need video, place the camera high and central and test the exact chair where you will sit.
| Model | Signal | Screen | Best placement | ASIN | |
|---|---|---|---|---|---|
| 1VTech DM221 | 1.9 GHz DECT audio | None | Parent unit near the stair opening | Check price → | |
| 2Philips Avent SCD843 | 2.4 GHz adaptive FHSS | 3.5 in | Same side of the house as the camera | Check price → | |
| 3VTech VM819 | 2.4 GHz FHSS video | 2.8 in | Directly below the nursery, one room in | Check price → | |
| 4Infant Optics DXR-8 PRO | 2.4 GHz FHSS video | 5 in | High and central, with a clear diagonal to the stairs | Check price → |
What a floor does to a 2.4 GHz link
A 2.4 GHz wave is about 12.5 centimeters long, roughly five inches. Small waves bend less around openings and lose more energy in dense material. Drywall, plywood and wood joists are mild obstacles. A poured concrete slab is not, and neither is a floor with a wire mesh for radiant heat, a foil vapor barrier or a suspended metal ceiling grid. The same floor can be transparent in one house and opaque in the next.
The path is rarely straight down. The camera sits in a corner, the parent unit sits in a bedroom, and the line between them crosses the floor at an angle, then a wall, then maybe a closet. Each material takes a bite. The signal that reaches the stairs is weaker than the signal that left the camera. A 2.4 GHz video link sends hundreds of kilobits to a few megabits per second, and when the error rate rises the picture freezes, blocks or drops frames.
The band is also crowded. Wi-Fi, Bluetooth, microwave ovens and a dozen neighboring routers share it. Frequency hopping helps a monitor dodge a busy channel, and a good FHSS unit will move around the interference. Hopping cannot recover energy that concrete absorbed. That is the distinction worth holding onto: interference causes dropouts that come and go, while a floor causes a loss that is worst in the same chair every night.
Ignore the range number on the box unless it is printed with a condition. A 1,000-foot claim is usually a clear line of sight outdoors, with no floor and no wall in the path. Through a downstairs ceiling and an upstairs floor, the useful distance is a fraction of that. The only number that matters is the one you measure in your own house.
Why DECT audio survives the trip
DECT in the United States runs around 1.9 GHz. The wavelength is about 16 centimeters, a little longer than 2.4 GHz, but the bigger difference is the job. A voice link needs a few tens of kilobits per second. A video link needs hundreds of kilobits or more. At the same transmit power, the slower link puts more energy behind each bit, so it can survive a weaker signal before it fails.
The failure modes differ. A dropped packet in a voice stream becomes a click or a short gap, and a parent keeps listening. A dropped packet in video becomes a frozen frame or a black screen, and a parent picks up the phone. DECT was built for a continuous conversation between base and handset, with frequency hopping and a link that holds rather than a link that shows. That is why audio often sounds fine through a floor while video stutters.
Be careful with the word better. DECT is not magic through concrete. It is more efficient with the signal it has, and its output is sound, which degrades politely. Video is a different bargain. The Philips Avent SCD843 uses adaptive FHSS in the 2.4 GHz band, not DECT, so it does not get the lower data rate that helps audio. It is a good small-screen unit, not a through-floor miracle.
Where to put the camera and the handset
Start with the path, not the furniture. The best route from a downstairs nursery to an upstairs bedroom is usually up the stairwell, a vertical shaft with less material than a ceiling. Put the camera on the side of the nursery nearest the stairs, and the parent unit on the side of the bedroom nearest the same stairs. A diagonal through two rooms and a hallway is worse than a short hop to the landing.
Mount the camera higher than the crib mattress and aim it down, but not on a shelf directly above the crib. A monitor is not a mobile, and a cord is a strangulation risk. Keep every cord at least three feet from the crib, anchor it to the wall, and use a mount that cannot be pulled over. A central wall gives a wider view and a shorter path to the door.
Keep the parent unit out of radio shadows. A metal bookcase, file cabinet, refrigerator or metal lamp can block more than the floor. Low-E glass has a thin metallic coating that reflects 2.4 GHz, so a windowsill is a bad spot even though it feels open. Keep the handset away from the router, microwave and cordless phone base.
The shape of the house matters as much as the material. A stairwell acts like a shaft, a chimney chase is a hole through the same floors, and a closet full of coats is mostly air. A short path through a refrigerator and a microwave can be worse than a longer path through an open landing. Walk the route with the parent unit in hand and watch the signal meter if the unit has one; a drop from four bars to two at the bedroom door is a placement problem you can fix.
Some monitors show a link quality icon rather than bars. Treat any change as a clue, not a score. The number that matters is whether the audio breaks up or the video freezes where you sit. A base unit matters too: a DECT base in a metal media cabinet or under a TV is a bad transmitter. Put it high, away from the router and the microwave, and keep the antenna vertical if it has one. The handset and base need to hear each other as much as the camera and parent unit do.
If video keeps dropping
Move the camera before you buy anything. Six inches can matter when the path crosses a steel beam or a duct. Try the opposite wall, a higher mount, or a spot closer to the stair side. Then move the parent unit: off the metal nightstand, out of the corner, closer to the door. A basic stand is cheaper than a new monitor, and a five-minute move fixes more dropouts than a new radio.
A second parent unit does not extend range. It receives the same signal from the same camera, so it will fail in the same places. A Wi-Fi extender can help a Wi-Fi camera if it sits halfway between the camera and the phone, but a dedicated FHSS or DECT monitor cannot use one. Do not buy a repeater for a system that was never designed to join one.
If the nursery has a concrete slab and video is unusable, decide what you need. Audio for the night plus a video check when you go up is a reasonable split. If you need a picture all night, accept a 2.4 GHz video unit and place it carefully. A 5 GHz Wi-Fi camera is not automatically better: it loses through walls faster than 2.4 GHz. Buy with a return window and test it in the room.
A ten-minute test you can run tonight
Put the camera in its final spot and the parent unit where you will sit. Close the doors. Walk to the far corner upstairs with the handset and listen for ten minutes. Run the microwave and the bathroom fan, then listen again. Clap downstairs to check delay; under a second is workable, over two seconds makes conversation useless. If the unit has night vision, turn off the lights and check the image from your chair.
The non-Wi-Fi shortlist lists the link type next to every model for this reason. If you are still deciding whether a monitor is needed at all, this piece is the more basic question. For a downstairs nursery, the answer is usually a simple audio unit plus a plan for the times you want a picture.
✅ Buy it if
- The nursery is on another floor from your bedroom
- You can place both units near the same stair opening
- You mainly need to hear the baby at night
- You will test the actual chair before the return window closes
❌ Skip it if
- You need a clear video feed through a concrete slab
- You will leave the parent unit in a metal cabinet
- You expect a second handset to extend range
- You want a 1,000-foot claim to hold through two floors
Will a baby monitor work through one floor?
Audio usually does, and DECT audio is the safest bet. Video may work, but it depends on the floor: wood joists and drywall are mild, while a concrete slab with rebar, a metal radiant-heat mesh or foil insulation can block most of a 2.4 GHz signal. Test the exact rooms before you rely on it.
Is DECT better than 2.4 GHz through walls?
It is more efficient, not magical. DECT sends a voice link at a much lower data rate, so each bit has more energy behind it and a damaged packet sounds like a click rather than a frozen screen. Both bands still lose signal through concrete and metal; the difference is how gracefully the link fails.
Where should the parent unit go in an upstairs bedroom?
On the side of the room nearest the stairs, at least a few feet from the router, microwave and any large metal object. Avoid a windowsill with low-E glass. Keep it out of a closed metal cabinet. Then test the actual sleeping position, because a nightstand at the head of the bed can be a worse spot than the floor near the door.
Does a second parent unit extend the range?
No. Both parent units receive the same signal from the camera. If one drops out in a room, the other will drop out there too. A Wi-Fi extender can help a Wi-Fi camera, but a dedicated FHSS or DECT monitor cannot join a generic repeater.
Last updated: November 2026
Update log: Initial publish — floor materials, 1.9 GHz DECT and 2.4 GHz path behaviour checked against manufacturer manuals; range claims described as outdoor line-of-sight only.