iPad Air 3G Signal

Well, only a few weeks ago I got a brand new iPad Air and from the very beginning the 3G signal bars have shown an average of 2 dots with a vodafone uk sim However when you use the speedtest app it struggles to connect to the internet. At first I thought this May have been vodafone uk's fault but I then decided to change to an ee sim as the 3G signal is faster and stronger in my area. With this ee SIM card it is still having the same troubles, I have normally 3 dots but at times it doesn't connect to the internet or when it does it is really fast. This has been testing it when it's been in the same spit and not moved at all. The other thing is I have an old ipad 2 on ee and it's positioned where the Air is and it connects to the internet first time very time. I have a feeling my problem lies with the iPad. What are the thoughts of the people? Anyone having the same problem? Any advice?

Thank you.