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RE: [Paparazzi-devel] 900 Mhz or 2,4 Ghz modem (Chris)

From: mark.griffin
Subject: RE: [Paparazzi-devel] 900 Mhz or 2,4 Ghz modem (Chris)
Date: Mon, 20 Apr 2009 09:23:17 +0200

I would avoid high power video transmitters in the 900 MHz ish band as
out-of-band spurious emissions and the "receiver blocking effect" can
seriously degrade the performance of a GPS receiver (~1300 MHz). Some of
the 900 MHz modems are also known to have affected GPS receivers.

According to an earlier discussion on this mailing list, the Digi 868
MHz modems do not work properly with Pararazzi telemetry as they are
designed for a ~10% duty cycle and cannot achieve continuous throughput.
The Radiotronix WI232EUR 868 MHz modem works very well with the
Paparazzi system in Europe and does not degrade the performance of GPS

Bluetooth can also be used for a datalink (~100 to 500m depending on
external antenna) and can co-exist with a Spektrum 2.4 GHz receiver.

Hope this helps.


-----Original Message-----
From: address@hidden
[mailto:address@hidden On
Behalf Of Adam
Sent: Friday, 17 April 2009 9:38 PM
To: address@hidden
Subject: Re: [Paparazzi-devel] 900 Mhz or 2,4 Ghz modem (Chris)

If you're outside Europe then 900 Mhz should have more range but the
downside is a slower data rate. Basically the higher the frequency the
more prone it is to noise and attenuation due to obsticals and distance.

As far as I understand Paparazzi does not require huge bandwidths so I'd
go for 900/868 depending on where you are.

On Friday, April 17, 2009, chris <address@hidden> wrote:
> If you are in Europe you will need either the 868 Mhz or the 2.4 ghz
> The 900 Mhz is allocated to cellular phones in Europe so there might
be problems.
> The 900 Mhz do have frequency hopping (Aerocomm) so they might get 
> away with interference but i don't know that for sure as i have never
used them in Europe.
> The 868 does not use frequency hopping AFAIK.
> If you are located elsewhere (US, Australia etc.) the 900 Mhz is a
good choise as is the 2.4 ghz.
> All depend to what RC transmitter and / or video transmitter bands you
will use.
> Try and use different bands for each service (RC, Video, Telemetry) I 
> use the 2.4 ghz Xbee pro, a 2.4 ghz RC receiver that uses FHSS 
> (frequency hopping spread spectrum) and plan to use a 2W 850 to 950
Mhz video transmitter.
> For example Futaba uses FHSS at 2.4 ghz (Futaba FAAST) Chris
> _______________________________________________
> Paparazzi-devel mailing list
> address@hidden

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