Thanks for reaching out on the Community @GazCBG
The Smart 5G Hub HH20C doesn't come with connections for an external antenna, and so we also no longer offer an antenna fitting service.
For optimal signal, try place the router by a window, preferably in the same side of your premises as the local or best suited mast. This may take some trial and error. Though you can contact Customer Service technical team who can point you in the general direction of your best mast.
Some customers opt to purchase their own routers which have the hardware specifications they are looking for, and install their own external antenna. This is not something we would be able to provide support with though.
There are some community pages you can find with users discussing their choices.
Hope this helps.
Ali
