Z fold 4 4g/5g signal

[Jp46]

Why do you get a better signal when the fold 4 is open on the main screen. 

When the fold 4 is closed and using the cover screen the signal decreses slightly 

2/3 bars when open 

1 bar when closed. 

Any suggestions why this happens. 

[nowdeleted]

I would expect a signal when the phone is open as its when you use it.
As for it been closed why would you expect a good signal if you are not using it.