Captain Jack said:
I was actually talking about the Squarial - not sure about the other more conventional one. Wasn't a square dish their selling point? What was the point of selling standard dishes?
The reason for the dishes is purely cost, the squarials (or Flat Plate Antennas as they're actually called) were very expensive to produce, so, they reduced costs by using dishes, which are pretty small and unobtrusive, as were the squarials, but it is of course the squarial which is what made BSB more memorable...
As for altering a squarial to pick up modern day transmissions, I found it hard to try and achieve that, even using modern technology added in place of the original, it's designed for Circular polarisation, and that's not easy to come by these days, and unless you find a high powered transmission, the H&V transmissions are difficult to tune into, I tried just that with my BSB squarial (isung my long gone Attisat FPA's mount which was aligned on Hispasat, to aid finding said satellite), and while I did get a signal, and had adjusted the settings of the receiver, all I got was an unstable, static-laden image which I could barely make out as Cuatro...
http://www.satellites.co.uk/forums/retro-tech/60728-ive-got-squarial.html
I think the polarity changing mod was through opening up the squarial and flipping the plastic sheets over, which reversed the polarity, so you could pick up Left hand instead of Right hand, and vice-versa...