I am not sure if this is the correct place for this query, but here goes!
During Dec 2012, I switched to BT and subscribed to BT Broadband. I was sent a Home Hub 3 on usual contract.
During May 2013, we were able to get BT Infinity, so I subscribed to that and the engineer came to fit the Infinity modem.
Since then the wifi has been pretty poor throughout the house, with only a good signal in clear sight within 30 feet of the HomeHub.
My query is...should I have been sent another HomeHub, as clearly the HomeHub3 is not coping with Infinity?
There was no reason to change the HH3 for Infinity. There are still many customers with no problem using the HH3.
There's no reason the HH3 shouldn't be fine as pippincp says. Installation of Infinity shouldn't make any difference to HH3 wireless performance ~ though of course it is possible that performance that was able to keep up with an ADSL connection cannot keep up with Infinity; for example even a perfect 811n connection won't match a good Infinity connection.
It is possible that you have placed the new modem so close to the HH3 that they are interfering. Try experimenting with changing the positions of both the modem and the HH3 and seeing how it helps the wireless signal.
If you install isSSIDer on a laptop that should help you experiment. Older versions are free: not sure if this is a good download ... http://www.techspot.com/downloads/5936-inssider.html
Tried the inSSIDer..it was quite informtive, it shows a drop of about 70% of the signal if I move upstairs. The hub does`nt seem to have much strength in it all, in fact, the inSSIDer program showed that multiple neighbours with SKY broadband overtook the signal my HH3 sent out.
The Openreach modem is about 25 feet from the HH3, so I doubt interference is an issue. Seems the HH3 is just poor!