Use caution when judging connections using the Wi-Fi signal bars; only seeing "full signal" next to the router may be correct, depending upon your device and router.
The newer Wi-Fi frequencies have much shorter ranges than the old ones, though they can be faster at shorter range than other connections.
The newer Wi-Fi 6E technology as supported in the iPhone 15 Pro and ProMax uses three frequency bands, 2.4 GHz, 5 GHz and 6 GHz.
- When connected to the 6 GHz band, a signal will in most cases not reach more than fifty feet.
- On the 5 GHz band coverage may also be fifty feet or less.
- Finally, the 2.4 GHz band is what you are usually connected to across a house or commercial building.
For those with technical minds, at two meters, free space path loss is 46 dB for 2.4 GHz, 53 dB for 5 GHz, and 55 dB for 6 GHz, or coverage on the 6 GHz band drops off around 2 dB in the first meter as compared to a 5 GHz signal, which itself drops off 7 dB more in that first meter than a 2.4 GHz signal.
This means you may see a lower signal in terms of Wi-Fi signal bars, but it may still be a faster, more robust connection than you had with past devices.
Since only a few newer Apple devices:
- MacBook Pro (14-inch, 2023) or MacBook Pro (16-inch, 2023)
- Mac mini (2023)
- Mac Studio (2023)
- Mac Pro (2023)
- iPhone 15 Pro or iPhone 15 Pro Max
- iPad Pro 11-inch (4th generation) or iPad Pro 12.9 inch (6th generation)
support Wi-Fi 6E, if you have a 6E-capable router your new device may be the first to use the newer frequencies and therefore may show a lower signal strength connected to the same SSID as older devices.
See this document for more on using Wi-Fi 6E networks:
Use Wi-Fi 6E networks with Apple devices - Apple Support