[MLB-WIRELESS] [TIB] A new offer has been added to TIB - 11/1 2/2002

[Craig Sanders]

On Thu, Dec 12, 2002 at 06:10:06PM +1100, Barry Park wrote:
> I can understand amping a directional antenna with a narrow signal
> spread, but what happens if someone amps up an omni, especially as the
> density of the mesh around the omni increases?

i agree with what evilbunny was saying about antennas and beam width,
there is a difference there.    in fact, i can think of some
applications where that difference could be useful - e.g.  point to
multipoint links with an omni on a tall mast.  if the vertical
beam-width is too narrow then every antenna pointing at it has to be at
approximately the same height.  with a lower gain omni antenna (and thus
wider vertical beam width), there's a lot more tolerance about heights.
so for this application, you're better off with higher output power
(whether via high power card or via an amp) and lower gain antenna.

i still don't see what's the difference between a) a 500mW AP plus an
omni and b) a 30mW AP plus a 500mW amp plus an omni.  

you still have 500mW of power going into the antenna, regardless of
whether the AP produces it or an amp helps out.

the only difference is that the 500mW AP costs about $1600, whereas a
30mW AP costs about $300 and the amp another $250-$1000.

AFAICT, the only difference other than price is that some people want to
have all amps been branded as 'evil' and perhaps have the topic
forbidden from discussion.


one other possible use for an amp is for high-speed long-distance
(10-15km and more) backbone links between regions, although it's
probably cheaper and simpler to just use a high-gain antenna here (15dBm
AP plus 24dBi antenna - ~2dB pigtail loss ~= 37dBm).




my main issue is that i don't like to see any technology dismissed out
of hand for essentially religious reasons.  amps can be useful in
certain circumstances, and they're no worse than any other method of
increasing signal strength.


> Won't the amped antenna be a PITA for everyone else?

it could be.  it could also be useful to others who want to connect to
the local omni node.  

any signal source could be a PITA for everyone else.  any wireless
network you're not a part of is just annoying noise.

craig

-- 
craig sanders <cas at taz.net.au>

Fabricati Diem, PVNC.
 -- motto of the Ankh-Morpork City Watch

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