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[Ham-80211] Aerocomm Modems

Bill Diaz william.diaz at comcast.net
Fri Oct 14 17:07:42 UTC 2005


Guillaume,
  See below:

>-----Original Message-----
>From: ham-80211-bounces at lists.tapr.org 
>[mailto:ham-80211-bounces at lists.tapr.org] On Behalf Of Guillaume Filion
>Sent: Friday, October 14, 2005 08:38
>To: TAPR Mailing List for Ham Radio Use of 802.11
>Subject: Re: [Ham-80211] Aerocomm Modems
>
>
>Le 05-01-23, à 18:26, Steve Lampereur a écrit :
>> Quick summary : 1 watt 900 MHS FHSS, 115.2 kbps $99
>> [...]
>> It appears that we could set up a DHCP sever and handle this like an
>> ISP. That would be truly cool, make it a TCP/IP network.
>
>It looks interesting. If you're using the ConnexLink model (serial)
SNIP

>
>BTW, anyone remembers the tree attenuation per meter for 900 MHz?

I have a number of Motorola Canopy 900 Mhz Access Points installed in my
area.  While it may be possible to accept some losses from trees, the real
issue is the "Noise Floor" on 900 Mhz in the area of operation.    

The Motorola Canopy 900 subscriber module receivers are spec'd at -93db.
However, the average noise floor in my area (suburban Chicago) is around
-66.  Our Canopy 900 Mhz subscriber modules must see a signal around -63 or
so before they can establish a connection.  This limits the range to a
maximum of about 3 miles with a clear line of sight path and less than 2
miles with a less than optimum path.  

When heavy tree cover must be penetrated, these losses and a high noise
floor may preclude a path.  I know because I am 0.6 miles from a 900 Mhz
Canopy AP and cannot establish a reliable connection.  The AP is at 300'
with a 9db horizontally polarized omni antenna.  The subscriber end is a 10
db horizontally polarized yagi.  The path includes at least 6 trees.

If you are in a rural area with little 900Mhz activity, your results may
vary considerably.  We have numerous high power paging transmitters in the
area as well as trunking systems etc.  Some users in rural areas report
reliable connections over 10 miles.  However, based on my experience, I
would STRONGLY recommend horizontal polarization regardless of location.

Bill KC9XG

>73
>-- 
>Guillaume Filion, ing. jr
>Logidac Tech., Beaumont, Québec, Canada - http://logidac.com/
>PGP Key and more: http://guillaume.filion.org/
>
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