i have some RECOM units - http://www.recom-power.com/ in the 78XX size. the ds - http://www.recom-power.com/ says they switch between 280KHz - 380KHz and typically 330KHz. now if these were used for rf wouldn't that be an issue if the switching frequency was in line w/ the freq you were using for the rf unit? is there a way to know exactly what freq the unit switches at? or am i way of in this thinking?

 

What component exactly you mean? Which model?
If it's an encapsulated switching regulator, you may find out it's frequency by putting the oscilloscope probe near the regulator or putting the probe on the in/ or output without connecting GND .

There will be some oscillation to see on the screen and since you know the frequency range you'll know what freq it is.

 

Put the scope on the gate of the switching MOSFET.

 

this is the version - http://www.recom-power.com/pdf/Innoline/R-78xx-0.5.pdf

and no scope . so will the frequency change based on current draw and incoming vs outgoing V? is there any math to figure it out or is the scope the way to do it?

 

With no scope, trust the datasheet!