We (as will most radio people) you should not have anything within approx a meter of your VHF antenna. More space the better.
This is not always practical on any boat.
With Ribs it can be easier.
If the boat has an A frame I will site the VHF on one side and the GPS on the other. If possible antenna cable on apart. One down each side of the boat.
Compas safe distance 1M, this is because of the speaker in the radio (has a big magnet).
Its just good working practice.
GPS's are very electronicly noisey.
Have seen lots of cases where they are sited to close to a radio or antenna cable run beside each other and you get "noise" on the VHF.
Re-route the cables and/or move the antenna apart problem solved.
Radio can be a black art.
Taken me years to get it right!!!!!!!!!