Re: KeyFob

[Nigel Orr <nigel.orr@xxxxxxx>]

At 10:35 16/01/00 -0500, you wrote:
>If you are happy with the existing 418MHz products, there isn't any
>compelling technical reasons to move to 433MHz.

The rest I can agree with wholeheartedly, but that sentence isn't _quite_
true.  One of the big reasons for allocating 433MHz instead of 418 is TETRA
mobile radio.  Simplistically, it's a bit like a mobile phone network, and
uses some bandwidth around 418MHz for the mobile units.  One provider is
http://www.dolphin-telecom.co.uk/
if you want more gory details.  If your
418MHz kit is well designed, then it should work just fine.  However, there
have been various reports of problems (eg people unable to disarm their car
alarms when close to TETRA base stations etc etc, which may be a reason to
change to 433 if problems start to arise.  It is a local effect however, so
418 may be fine.

According to one note I have read, TETRA on the 418MHz band should be
phased in over the next few years and will only be used for the mobile
units, not the base stations.  I understand the current problems are from
TETRA base stations broadcasting close to 418MHz and receivers which don't
tune sharply enough.

>There should be either a small round sticker at the back with the
>frequency printed on it or it is mentioned on the product label.

It should certainly say MPT1340, the low power approval standard, but I
don't think they are required to state the frequency as well (I may be
wrong on that though... it's nearly a year since I last actually built
anything with a 418MHz link...)

Nigel


------------------------------------------------------------------------
For the fastest and easiest way to backup your files and, access them from

anywhere. Try @backup Free for 30 days.  Click here for a chance to win a

digital camera.
http://click.egroups.com/1/337/3/_/2065/_/948100902/

-- Talk to your group with your own voice!
-- http://www.egroups.com/VoiceChatPage?listName=ukha_d&m=1