I think this must have been an article from a while ago aimed at AM or FM radios as the radios on 2.4 are way less susceptible to interference. None of my models have suffered with any form of electrical interference since I changed to 2.4 from FM and previous to that 27Mhz which was shocking!. As previously mentioned I have 18 aircraft -mostly out-runners up to 1100w , a few in-runners-(ducted fans) and at the moment 5 boats (1 with twin in-runners, 1 with twin non suppressed 380s, 1 with single suppressed 380, 1 with twin non suppressed 540s, and 1 with a worn out old Graupner monoperm.
I have run 2 brushed boats together on 1 TX and a brushed and brushless on the same TX both with single wire RXs in each boat paired to the TX) with the boats 1ft apart at times with not a hint of a problem (RECs in the bow). I have always made sure the aerials are not in line with pushrods or near anything that might create any sort of magnetic field, and RXs as Doug said, on the opposite side to anything of that nature. Also as mentioned, any twin aerial RXs should have each leg at as near to 90deg as possible or at least 1 forward and 1 aft (
planes
and boats)
Not sure If I'm doing something right or it's the radios I'm using (5 different types- 2 are HK cheapo 2.4s- general lack of serious outside interference or if I'm just plain lucky, but I have enough of a variety of installations to show that in my opinion, if you are having a problem on a 2.4 set-up there must be something quite unusual happening.
I'll bet it would be something easy to fix, (like first take your gear out and test it to make sure it's not that, then look at aerial/ REC placement, twisted/coiled wiring etc. I noticed that the REC aerial on your boat Ron, goes over the top of the steel rudder pushrod -could be something as simple as that. You just have to go through things step by step until you find what's causing the problem (obvious statement I know)
Doug mentioned ferrite rings which are a good idea (I found some clip on ones on HK which you can put on leads easily) I also use UBECs on all my
planes
which have a ferrite ring fitted which are a good bit of insurance.
John B