Ed,

You mention frame drop outs with a PCM receiver. I believe it should still be common practice to perform initial, new plane, range tests with a PPM receiver, not with PCM. Unless the drop out count becomes pretty high the PCM receiver will not indicate the interference, via a "lock out", where the PPM will much more readily make it known. That's why the advice given to the newbies is to range check first with a PPM, then later, after you are fully satisfied that all is as it should be, install a PCM receiver. It also helps a lot if the user understands how a PCM receiver works, what it does, and knows how to set the "failsafes".

As far as drop outs in general, unless the operator has some pretty sophisticated test or telemetry equipment at the site they will have no way of seeing just how much of the radio signals are lost or interfered with in flight. Yes, there's some equipment on the market that lets you see how many glitches you had after you land, but it's going to be pretty pricey, not to mention unusual, to see someone at the field that has the telemetry system that let's them continuously monitor the signal strength and drop outs as they are flying. If they did have it they would be too busy "watching the gauges" to fly the plane and would crash anyway.

In the end, the use of good equipment, secure connections, and proper range checks with a PPM receiver will tell you all that you need to know. If you can pull off a range check of 125 feet or more, engine off and engine running without encountering any issues then you're generally good to go. It's easy to find a boogey man in every closet. Somethimes you have to make a decision is the one in your closet as to whether or not the one in your closet is actually a threat.