[amsat-bb] Re: A0 40 replacement

M5AKA m5aka at yahoo.co.uk
Thu Sep 5 09:37:01 PDT 2013

> But what if the SDX that flew on ARISSat, or the one
> that will be developed for the Future of the Fox series could be "sold" (or
> given) to the university cubesat community as a radio capable of being used
> to deliver science data?

Hi Zach, 

Unfortunately there goes the CubeSat's power budget. 

The SDX transponders have an overhead, not just in terms of the physical space they occupy, but the amount of power they consume. 

I believe the most efficient SDX transponder has an overhead of some 350 mW above the power consumed by an analog linear transponder and a linear transponder itself would consume more power than a standard 9600 bps CubeSat telemetry module.

So it appears to be a non-starter for 1U CubeSats. Might be feasible on 3U CubeSats but it would mean much less power would be available for other experiments on the CubeSat. 

The question is what's in it for the CubeSat team ? The answer may be a higher data rate, the existing 9600 bps just isn't fast enough. In theory, depending on the modulation employed, a 30 kHz bandwidth SDX transponder could generate a 96 kbps downlink which is much more useful. To some the trade-off of power budget for downlink speed may prove appealing. 

At the moment it's all theoretical but certainly worth considering when a FOX-2 SDX transponder has been proven to work in space.

73 Trevor M5AKA

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