27995-27997 RF Modules...

Archiver

Tuesday, 07/16/02 @ 10:15 AM

Hello All,

Do any of you have any more information about the 27995-27997
SIP/Fixed Antenna RF Modules? The PDF files from Parallax and from
RFDigital are just basic hook-up with sample code information and I need to
know if they do any error checking on-board, or is that up to the user and
the Basic Stamp code. Are there other PDF doc's that I've missed, such as
on the 27986-27988 module series? I'd like to use a pair of the 27997
Transceivers, but would also like anyone's practical experience as to the
150 foot range being useable indoors.

Thanks for the feedback,

Tim


Timothy Medema
CrystaLite, Incorporated
3307 Cedar St. (425) 745-6000 800-666-6065
Everett, WA 98201 Fax: (425) 257-0232

www.crystaliteinc.com
<mailto:timm@c...>timm@c...


The information transmitted is intended only for the person or entity to
whom it is addressed and may contain confidential and/or privileged
material. Any review, retransmission, dissemination or other use of, or
taking of any action in reliance upon, this information by persons or
entities other than the intended recipient is prohibited. If you received
this in error, please contact the sender and delete the material from any
computer.

Archiver

Tim,

Please check out message #23163 for my experiences using the RF
modules and for some antenna hints.

I used the modules with the built in loop antenna, and acheive around
15m indoors (without any careful placement of the antenna) and I
expect when the Tx antenna is properly located to achieve around 20m
indoors. The limit for indoor reception range comes from 2 main
factors:

1) Reflections which result in dips in the coverage (a common indoor
problem)

2) The fact that the 433.9 frequency is shared with other equipment,
some operating at higher power (typically remote thermometers and
other remote controls etc). This can be overcome by using a simple
ACK (to force a retransmission) from one of the remote units to be
sure that the message got through.

Error checking is recommended in any case using any form of RF medium
for communication. I find a simple checksum byte at the end of the
message is sufficient to tell if the message was received OK or not.

If using the raw (ie, no onboard preprocessing in the module) Lynx
modules and providing your own coding: The RF modules use Pulse
Amplitude modulation. The bandwidth is therefore directly
proportional to 2.5 (approx) times the data rate (in bps). Thus, the
higher the data rate, the larger the spectrum the power is spread
over. Thus, maximum range will be obtained with the lower data rates
(since the RF output of 1mW is fixed).

Dare

--- In basicstamps@y..., Timothy Medema <timm@c...> wrote:
>
> Tuesday, 07/16/02 @ 10:15 AM
>
> Hello All,
>
> Do any of you have any more information about the 27995-
27997
> SIP/Fixed Antenna RF Modules? The PDF files from Parallax and from
> RFDigital are just basic hook-up with sample code information and I
need to
> know if they do any error checking on-board, or is that up to the
user and
> the Basic Stamp code. Are there other PDF doc's that I've missed,
such as
> on the 27986-27988 module series? I'd like to use a pair of the
27997
> Transceivers, but would also like anyone's practical experience as
to the
> 150 foot range being useable indoors.
>
> Thanks for the feedback,
>
> Tim
>
>
> Timothy Medema
> CrystaLite, Incorporated
> 3307 Cedar St. (425) 745-6000 800-666-6065
> Everett, WA 98201 Fax: (425) 257-0232
>
> www.crystaliteinc.com
> <mailto:timm@c...>timm@c...
>
>
> The information transmitted is intended only for the person or
entity to
> whom it is addressed and may contain confidential and/or privileged
> material. Any review, retransmission, dissemination or other use
of, or
> taking of any action in reliance upon, this information by persons
or
> entities other than the intended recipient is prohibited. If you
received
> this in error, please contact the sender and delete the material
from any
> computer.