The helical aerial was an official Robbe item. It would reduce the effective range of the set by about 25% though. Not a major issue in either a surface boat, or probably even a submarine. We don't run them that far 'off shore' usually, they are a pretty small thing to keep track of at a distance.
In the debate over F14 or more modern budget sets, I would still go F14. I have recently commissioned a corvette model and needed the flexibility offered by the internal layout of this style of set. I am currently using the FC16 Boat and Truck variant, which is much the same beast with a few extra bells and whistles. I had the option of this or a 2.4G option, but I cannot get over the 'cheap quality' aspect of these types of set. Looking on various forums, the quality control on some of these strangely well respected sets is dodgy to say the least. So, the suppliers replace faulty units, which is great. But what if the fault manifests itself while the model is in use? Not such an issue with a slow, scale model, but, given the choice, I will always opt for quality over economy. Only today I was idly browsing through the no1 online store for RC stuff, looking for brushless options for a U-Boat. Great search engine, took me straight to a fairly expensive motor by some mayhemmers standards. Checking the six reviews, one bought three motors and one of the three didn't work, one had duff bearings out of the box, and the other four were glowing reports about the motor. So that is two out of eight not working, not very scientific and full of holes as a theory, but then so is the blind belief that cheap is always best. Best advice, buy the best that you can afford, but do your research first.