ADSL Router transmit power

Previously with the Post Office - Zxyel router, I recently changed to sky with the Q router.
The Zxyel router covered the whole of my small apartment, but the Sky Q does not.
I have tried the older sky hub router and it has exactly the same low transmit power.
The TalkTalk and BT routers appear to give a very strong signal (my neighbours' signals are both stronger in my flat than the sky router.
Does anyone have definitive info on the relative transmit power / coverage of various routers?
Is there a hack to increase transmit power for any of the above routers?
(Yes I do realise that the transmit power of my wifi adaptors are also a factor but I have no way of measuring their transmit power).
A call to sky was a waste of time, all he knew how to do was reset the router - virtually no technical knowledge.

If your 'Zxyel router ' was that good then use it as a WiFi Access point (do a search if you do not know how to connect it up).
I used to use up to six old routers for that in my large house.

re ... Yes I do realise that the transmit power of my wifi adapters are also a factor but I have no way of measuring their transmit power). yes you do, I presume you use Windows . try ipconfig.
I use Linux.

On Windows the following command will provide some information on relative signal strengths.

netsh wlan show networks mode=bssid

Thanks APTMAN, yes the Ztxel router works well as an access point.
ipconfig doesn't show transmit power.
I used Linux for years but now need active-x for an essential app.
The latest version of Win10 looks remarkably like Cinnamon!

Thanks Eeeps, yes it gives a percentage, but a percentage of what figure?