Using a 50ft and 100ft Cradlepoint cable example, is the 100ft cable going to hurt my signal?
The short answer is 100ft should be okay assuming you have a good signal outside from the cell tower. If you need to go longer that 100ft, or if you have a marginal signal outside the building, you'll want to consider different antenna or lower loss cabling options.  In this case, please contact us and we can help you find the best solution.
More details:
There is 0.0493dB of signal loss for every foot of LL400-FLEX cabling at 900Mhz. Since Cellular signals cover several bands, 900Mhz is a good frequency for considering average cellular signal calculations. For a 50' cable, you have 2.465dB of signal loss (0.0493 x 50). In a 100' cable, you have 4.93dB of signal loss (0.0493 x 100). If you are using an omnidirectional outdoor antenna, the gain of the antenna is likely around 5dBi so you are still in the positive (5dBi - 4.93dB = 0.07dB). If you have a good signal outside, then this won't be a problem. If you have a marginal signal outside, then you may need to use a directional antenna with higher gain or a lower loss cable. However, another consideration is that you are getting the antenna up and in the clear where it can better pick up the signal from the cell tower and you are overcoming the wall obstructions of the building. This does make a considerable difference and is not easy to measure and do a hard calculation.
If you have a case where you need a cable for your CradlePoint external antenna longer than 100ft, please contact us and we can help you find the best solution.