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Re: Doppler correction?



Hi John,

InstantTune updates the frequency every second.
There is no simple way to change this since it
is driven by InstantTrack/OrbitDRV which updates
the satellite velocity every second.

I haven't checked Cute-1 but I would guess
that the max, Doppler-shift, change rate is something
like 100 Hz per second or so when it is directly
overhead. Is this what you are seeing?

That would mean that your receive signal would
"chirp" about 100 Hz low before catching
up again for the time when the sat is overhead.
Is Hamscope unable to keep up with this?
(I have never used it and I don't have a copy
handy to try it.)

Is this the problem you are seeing or is it
something else?

What kind of radio are you using?
The tuning step size in InstantTune depends
on the specific radio. Do you think the step
size is too small?

When you say it doesn't keep up, do you mean
it is actually losing hertz or it does not update
the radio fast enough to make the AFC happy in
Hamscope?

Thanks!
Tony AA2TX

---

At 10:59 PM 11/10/2003 +0000, johnheath wrote:

>Any good ideas out there?
>
>Taking Cute-1 telemetry with Hamscope.
>
>Works fine,  but for near overhead passes ITUNE can't keep pace with
>the Doppler.
>I am using up to date Keps. Accurate time on the PC, and  AFC set in
>Hamscope
>
>It seems like I need  ITUNE to update the rig at more frequent
>intervals. Can this be done?
>Or is there another solution?
>
>73
>John  G7HIA, M3BBX

----
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