| Receiver design is old hat and is not the least bit as demanding as | rocket science.
Even rocket science isn't that complicated -- we certainly had rockets centuries before we had radios, and we got the modern liquid fuel rockets not too long after the radio was invented.
`Rocket science' is quite the misnomer -- at their basic level, rockets are VERY simple.
| There is nothing new under the sun,
That is definately not true, especially when talking about electronics. Granted, with radios most changes are evolutionary rather than revolutionary, but things are definately improving.
Modern R/C receivers seem to not change the RF part of the design too much (though that's changing too), but the parts after have certainly changed a lot with the introduction of DSPs and microprocessors.
| except technology to make them cheaper.
... and smaller, and better.
Ultimately, you want your receivers to be small, to reject interference well (and get adequate range) and to be cheap. If you're willing to make it larger, you can get better interefence rejection by adding better or more filters. And by spending more money, you might be able to make it smaller again. But ultimately it's a number of tradeoffs, and most receivers that we use are not that great at rejecting the various forms of interference they may receive. They're good enough most of the time, but signals on certain other frequencies can cause them problems.
At the other end of the spectrum, consider the typical ham 2 m repeater. Thanks to the awesome duplexers (filters) they have, they can transmit at 1000 watts only 600 kHz away from the signal that they're receiving on, on the same antenna, and yet the receiver is still incredibly sensitive. Of course, they're physically quite large, and not really cheap. (Small, cheap, good -- pick any two. In this case, they pick `good' twice and nothing else.)
| R&S Systems made 72 MHz receivers the size of chewing gum | packs that were fantastic then and today.
Actually, as time goes on, the RF spectrum gets more and more noisy. What worked back then may very well not work as well today. Or if it does work, it may just be because it's in a bit of spectrum that's still lightly used (and the 53 mHz band certainly qualifies.)
I don't know anything specially about R&S's receivers, but if they're more than 15 years old, they're probably not even narrow band, and so they'll be totally unsutiable for use today at all.
| Multipath gave my Kraft Series 82 FM receiver some difficulty | whenever I flew over the power lines at the end of our field. A | little bit of a down elevator glitch, otherwise, it was okay. I know | this is what caused the multipath because I had no problem before | the power lines were installed.
Multipath again? Again, it's only one of many sorts of interference, and it's rarely a big problem for us.
Yes, a power line could re-radiate a signal back to cause multipath interfence, but it would be very weak. A large metal building, fairly close, would be required to create a multipath signal that's strong enough to really interfere with our radios. We almost always have direct line of sight to our planes, so any multipath signals are usually much weaker then the primary signal and rarely cause problems.
Power lines can and do create interference of other sorts, however.