"Meindert Sprang" wrote in message ...
"Parallax" wrote in message
om...
I really don't know how
a radar antenna works on small boats. If it is just a rotating dish,
it oughta work with the right transducer.

Most, if not all, radar antenna's on boats are slotted waveguides. That is a
piece of rectangular tube with slots in it. Such a waveguide and slots
resonate on 10GHz and will not transport and transmit cellphone signals at
900MHz (aka 0.9GHz).

Apart from that, the cellphone system works with datapackets in very tight
time-slots. The system compensates for the distance between the tower and
the phone (TA: Timing Advance) with a TA value between 0 and 63, for every
550 meters the phone is further away from the tower. This imposes a hard
limit on the maximum distance of 550 x 63 = 34.6km or 18.7 miles. So no
matter how high your antenna is and how much power you have available, 18,7
miles is the limit.

Meindert


Meindart:

Thanks for the useful info, I agree, the waveguide antenna wouldnt
work. Boat radar doesnt use a parabolic antenna with the waveguide
horn at the focal point? Why not?