[amsat-bb] Re: General Telemetry Question

[David Johnson]

Hi,

In the case of FUNcube the on board sensors give their readings as n bit
values when they are interrogated. This data is agregated into a data frame
for transmission using forward error correction to improve the s/n ratio.

The problem with on board conversion is that you would have to store the
scaling/offset/logarithmic values for all channels on board, in rom.

These are usually only characterised during thermal cycling / illumination
testing etc and would have to be uploaded to the satellite rom. Not
necessarily a simple task.

It is easier to do it on the ground where we can tweak the calculation
factors.

73

Dave, g4dpz
On 9 Dec 2013 13:52, "Dave Marthouse" <dmarthouse at gmail.com> wrote:

> I noticed over the years that satellite beacon downlinks transmit their
> telemetry in a form that must be translated by a telemetry app to their
> engineering values. Since the information is transmitted from the
> satellites
> why not provide the engineering values in the downlink without the extra
> step having to be done on the ground?  What is the logic of doing this?
>
>
>
>
>
> Dave Marthouse N2AAM
> dmarthouse at gmail.com
>
>
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