I have a descent set of probes that are rated at 100MHz, overkill for my current scope, only rated at 15MHz, but I am looking at a couple of different options for used scopes right now, some rated as high as 400 MHz. Unfortunately, most of these don't come with probes, and if they do there is only 1 (For a 4 channel scope). As long as I am looking at a signal that has fewer than 100MHz, would it be an issue to use the lower rated probes with a scope that can easily support more than that? When you exceed the rating of your probe what happens? Do you just loose definition on your signal?
It is safe to use a probe with less bandwidth than your oscilloscope. The probe acts like a lowpass filter so if you do use it to display a signal with greater bandwidth than the probe, the signal display will be degraded; e.g. a square wave will begin to look like more like a sine wave depending on the difference between the signal frequency and the probe bandwidth. Also, a low bandwidth probe may have more capacitance than a high bandwidth scope is designed for. That will make it difficult to compensate the probe and will also degrade the display. Unfortunately, probes rated to work with oscilloscopes having bandwidths on the order of 400 MHz can be rather expensive. However,it may pay to get one probe that can make full use of your oscilloscope's bandwidth and settle for less on the other probes. That will depend on the types of signals that you will be observing.