[amsat-bb] Re: Two hundred 437 MHz satallites launch March 16 + WebSDR

[Wouter Weggelaar]

Howie,

CDMA is actually actively promoted by the ITU. Indeed all the details have
to be published before launch, so everyone can demodulate it.

Citing from the ITU satellite-amateur handbook:
*"Amateur and amateur-satellite systems should have technical
characteristics that provide worldwide interoperability, and allow
origination, relay and termination of communications independent of other
radio services. Design emphasis should be placed on reliability, robustness
and flexibility of reconfiguration for efficient emergency communications.
Multiple access techniques (FDMA, TDMA and CDMA) should be selected for
optimum spectrum efficiency and frequency reuse. The selection of
modulation techniques should take into account resistance to interference
and immunity to adverse propagation conditions."*

I have been researching this for the QB50 mission, but strong pressures
(mainly from the US) within the project killed the idea early on.

The US is now actively putting satellites in 70cm with experimental
licenses, which unfortunately means they could use CDMA without providing
the spreading codes. The (majority of the) rest of the world is still using
the amateur satellite service.

Using CDMA would be beneficial for sharing the spectrum, but required
coordination as well. I was trying to standardize the parameters (for
QB50), so the IARU could be handing out orthogonal codes to satellite
teams, so avoid clashes. But welcome to politics.....

Wouter PA3WEG


On Tue, Mar 4, 2014 at 10:16 PM, Howie DeFelice <howied231 at hotmail.com>wrote:

> Yes, that is true, so are these licensed under an authority other than
> amateur radio ? If they aren't then my questions stand.
>
> Date: Tue, 4 Mar 2014 14:55:52 -0600
> Subject: Re: [amsat-bb] Re: Two hundred 437 MHz satallites launch March 16
> + WebSDR
> From: damonwa4hfn at gmail.com
> To: howied231 at hotmail.com
> CC: amsat-bb at amsat.org
>
> 70 CM is not just for the ham bands, it is a shared band check the
> ruleswa4hfn Damon
>
> On Tue, Mar 4, 2014 at 2:30 PM, Howie DeFelice <howied231 at hotmail.com>
> wrote:
>
> Is CDMA an authorized emission type for the Amateur service? What is the
> chipping rate/bandwidth of these? Don't the PRN sequences need to be made
> public so as not to be classified as "encryption" ? Detailed specs on the
> Sprites is in short supply. Has anyone done a link budget, seems like allot
> of spreading gain is required to hear 10mW form a 300km orbit which
> translates into allot of bandwidth in a part of the band usually reserved
> for narrow band modes. The lack of transparency on many of these projects
> that use the amateur bands seems to run against the spirit of amateur radio
> in my opinion.
>
>
>
>
> Howie
>
> AB2S
>
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