On Sat, 24 Nov 2012 17:36:06 +0000, Andy Burns
wrote:

Mark Carver wrote:

I read somewhere that they were able to horse the 2100 MHz transmitters
into their existing 1800 MHz antenna systems, and therefore have rolled out 3G
much faster than VF and 02 who have had to duplicate 2100 MHz systems
alongside 900 MHz ?

Vaguely related, I found this blog post showing the inside of a GSM base
station cavity duplexer quite interesting ...

http://laforge.gnumonks.org/weblog/2012/11/22/#20121122-inside_cavity_duplexer

That's quite a filter pair. Nine pole elliptical. Very steep sides
with nulls in the adjacent bands. Easy enough to do the electrical
design, but implementing it mechanically is not so simple.

d