If you operate a Multichannel VPN Router with multiple UMTS/HSPA+ modules, the immediately adjacent stub antennas would interfere with each other. Here, it is worthwhile to place the antennas at a little distance to the router and each other. This is easily possible with the UMTS/3G mini window antenna at a reasonable price. It is self-adhesive and can be attached from the inside of the window. The 3m cable gives you plenty of flexibility for choosing the location of the router. Despite its small and inconspicuous appearance, this omni-directional antenna may gain up to 2 dBi.