Prepaid wireless broadband performance upgrade help

[invetel]

Current system is Telstra prepaid SIM in a Telstra Turbo USB modem. My location of use has 3 bars signal strength (speed and delay quite bad a lot of the time). I have over $150 credit on the SIM.

Desire improvements are:

1. Change the modem to a WIFI type (MF60, MF91?) that have connector for antenna. Prefer modem with speed capability adequate for Skype use.
2. Add external antenna to the WIFI modem to improve speed and reduce time delay. Current upload speed is inadequate especially during heavy internet traffic times.

Please help on the following questions:

1. If I get a MF60 WIFI modem can I put my current SIM in and start using. Can I do the same if the modem is the MF91 (does a 4G modem require a new SIM).
2. If I get a MF60 WIFI modem with a new SIM can I keep the new SIM un-activated until I need to use it in a year's time.
3. Is this antenna suitable for improving the signal strength
   http://www.ebay.com.au/itm/170938585335?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649

Thanks from John

[Steph · Accepted solution]

Hi invetel, 

The answers to your questions are as follows: 

1. Yes you can put your current SIM card in, and start using it straight away, and you can 4G without a new SIM card. 

2. You can keep the SIM card unactivated, however there is a possibility that after 6-12 months it will be reassigned to another service.

3. That antenna isn't a Telstra antenna, so I can't comment on it's suitability