sooooo.. . IPD is nothing more than a normal FM reciever, with some signal reception and amplification circuits thrown in, a PCM-type failsafe function thrown into the mix, and better resolution (within the limitations of the PPM timing window).
So, it can still go into "failsafe" (how do you program that with your standard FM radio?????) which means a lockout, and being FM is more prone to interference than PCM, no matter what kind of fancy receiver doo-dads you come up with to increase sensitivity. It seems that the way that sensitivity is increased, by actually widening the frequency "window" in the RF and IF amplifiers, would make it more prone to interference at the lmiit of sensitivity, which is pretty darned undesirable if the receiver is losing signal due to interference from something on the very edge of the frequency. You are still limited to the "narrow band" for your frequency, for total frequency bandwidth, and being that these "bands" are really bell-curve areas of sensitivity, the outer edges of that "sensitivity range" would actually be outside the desired 10khz (if I recall properly) of maximum frequency deviation allowed by the FCC for transmitters.. . . .
You know. . .U-control and solid steel cables is starting to look more attractive all the time.
There are advantages and disadvantages to every signal and receiver design. The ABC&W from JR is not living up to it's hype, dual conversion still has the upper hand, IPD gives you the worst-case scenarios of "lockout", FM is subject to getting hits from somebody sneezing hard at the other end of the flightline, and AM is a disaster.
Think I'll go over to HAM band so I can transmit 500 watts. . . . . Interfere with THAT!!!!!