some Iphones still emitting high levels of RF when in airplane mode

Hi,

everyone in our family has iphones.

I recently got a EMF reader and tested the RF of our iphones while running in normal mode and airplane mode.

NORMAL MODE TEST:

Iphone was running in normal mode and emf reader was placed next to iphone.

The EMF reading registered highlevels of RF as expected.

AIRPLANE MODE TEST:

Iphone was running in airplane mode and emf reader was placed next to iphone.

The EMF reading registered low levels of RF for two Iphones but still registered highlevels of RF for the other two iphones. I tested this multiple times and got the same result.

I was expecting the EMF reader to register low levels of RF when the phone are in airplane mode.

Why would some iphones still register highlevels of RF while in airplane mode?

I'm wondering if there is some option in the phone that causes it to still try to send RF signals while in airplane mode ?