Q: Problem with intermittent internet on all Macs

Just wondering if anyone can help. I have had an iMac for 5 years and it has always had really intermittent internet - despite having it in 3 different houses (e.g it isn't the internet coming to the property that's the problem). Eventually I had to get a USB booster to plug into it but this still didn't work and often the internet connection drops out. I thought this was just because it was relatively old. However, I just bought a new Macbook Pro and am having the exact same issues with this.

Any ideas?