AVR-Chat

On Wed, 07 Feb 2007 23:03:41 -0600
 Thomas Keller <tjkeller1@alltel.net> wrote:
> Cat C wrote:
> > I thought nobody sells 900MHz zigbee, do they?  I'd
> think I should get 
> > longer range, and maybe less interference ... am I
> wrong?
> >   
> 
>  There are some commercially availabel 900 Mhz Zigbee
> products.
> 
> Downside #1:  900 Mhz Zigbess does *NOT* offer 250 Kbps
> data rate, 40 
> Kbps, IIRC.
> 
> Downside #2:  NO, 900 Mhz Zigbee does not offer any more
> range
> 
> Downside #3:  900 Mhz Zigbee is considered an abomination
> by most Zigbee 
> users, and the Zigbee Alliance barely evenb acknowledges
> its existence.
> 
>    There are *NO* apparent afvantages top choosing 900
> Mhz Zigbee.
> 
> Oh, Downside #4:  900 Mhz Zigbess is only approved for
> use in the USA, IIUC.
> 
> tom
> 

In the US, 900MHZ is shared with point-point
studio-transmitter links, with RFID, and with hams.
Studio-transmitter links are primary, hams are secondary,
not to interfere, and RFID is unlicensed frequency hopping
spread spectrum. 

Its not significantly better (in terms of range) than
420MHz. Antennas are half the size for the same gain.
Patches are ugly; if you try to make them out of circuit
board, you get, at very best, 3db of gain and you get more
than that with a dipole! You do get two-axis
directionality, however (more beam-like) but the beam width
tends to be 90-100 degrees in both axes. Some sort of a
small yagi would give you a LOT more range.

Jim

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