When you are setting up a antenna to get a better signal and improve speeds you need to take into account the cable you are going to use and the signal loss (attenuation) that will occur over various distances. Thankfully there is a handy calculator provided by Times Microwave systems® that will compute that for you:
By entering the cable type from the drop-down box and plugging in length you can instantly see the results. For runs over 20 ft I recommend high quality cable such as LMR-400 for its superior low loss capability.
You will observe that different frequencies have different loss characteristics – with 1900MHz losing more signal over distance than 800 MHz.
Take into consideration the gain of the antenna you are going to use and subtract the signal loss of the cable to get the result, and remember that an amplifier will negate this loss and increase signal strength.
The calculator can be found here.