[exim] Off-Topic: Antenna for BT Voyager wireless router?

I know this is horribly off-topic for this list, so please accept my
apologies, but I also know this list is well-populated with highly
knowledgeable IT professionals based in the UK, so please bear with me...

Does anyone know whether it is possible to replace the antenna on a BT
Voyager 2091 wireless ADSL router, and if so, what connector type I
should be looking for, or alternatively where I could more usefully be
asking this question?

Many thanks and apologies again,

John.