BoatBanter.com - cellphones

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On Wed, 29 Oct 2003 08:53:39 +0100, "Meindert Sprang"
wrote:

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.

This is true for GSM, but not for AMPS and IS-95 CDMA widely used in
North America. I have no idea about distance limits for D-AMPS which
is TDMA, but it will fall back to AMPS anayway.

In Sweden we have some extended range GSM sites allowing up to 70km
distance, but they don't cover the majority of the coastline. This can
be a problem sometimes, that's why i have an old NMT450 cell phone
installed as well. With an antenna 18 m up, and 15W TX at 450 MHz, the
range is impressive, to say the least.

/Marcus

--
Marcus AAkesson
Gothenburg Callsigns: SM6XFN & SB4779
Sweden
Keep the world clean - no HTML in news or mail !

Parallax,

As Meindert alluded to, a small rotating focused array antenna in an
analog radar set is cheaper to make than a focused parabolic when the
gain of the parabolic is not needed. Really large stationary arrays are
used on radar that is computer focused, such as the USN Aegis missile
cruisers. They are 1 million watts on each side I think. Each element
in the array has it's own driver. Far too expensive for most pleasure
craft.

Also the frequency of radar is to far away from the cell frequencies for
it's antenna to be effective.

Regards, Ron