75ohm RG59, for psu testing with scope?

[rwgast_lowlevellogicdesin]

I have tons of 75ohm Bnc connectors and cabling around. I cant even find 50ohm cable anywhere locally! I mostly use this stuff for A/V and RTL-SDR antenna stuff.

I know that using 75ohm for RF when just receiving has negligible effects when plugged in to a 50 ohm antenna jack. Anyways Ive done a lot of reading on DIY bnc scope probes. I plan to build a very short set, maybe 6 inches for some differential PSU ripple testing. I was curious on te scope end, the 50ohm I always see is in parallel with the scopes input, obviously causing a voltage divider.. I guess my question is should I just use 50 ohm termination and series dampening resistors, or 75ohm to match the impeadence of the cable? Im more worried about reflection than anything else if I use the wrong resistors, Im only trying to get 25mhz of bandwidth so ill keep the cables under quarter wave length of 25mhz and all that good stuff, just wondering if using 75ohm parallels to make the voltage divider is necessary (since this is obviously not an even 2x probe) or if using 50ohm's and just writing off the mismatch is a better idea?

[Performa01]

In order to get good pulse response, you want to avoid reflections.
Ideally, both ends of the cable should be terminated with its characteristic impedance, but in many cases it is enough to just terminate the receiver correctly.
That means, having a 75 Ohm pass-through terminator at the scope input is mandatory. If probing a very low impedance source, a series damper resistor at the source end might be a good idea too - the value depends on the actual source impedance at higher frequencies and you would have to try out several values <75 Ohm to achieve best signal fidelity.
In general, impedance matching is not an issue for wavelengths greater than 10 times the electrical cable length. From memory, I think the actual (physical) length of RG59 is about 2/3 the electrical length.