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Re: AO-40 beacon frequency question.

"Michael P. Olbrisch" wrote:

> > [nu8i]
> > I know that the nominal frequency is 2401.323, but is there
> > an accurate estimate of the actual value, and it's stability? By
> > subtracting out the Doppler and comparing it to my receive
> > frequency I could get a good idea of how much drift I am seeing
> > in my downconverter.
> Try catching the satellite when it is at apogee, and apparent
> range is steady.  If the satellite appears motionless, from your
> station, there is no Doppler.  Check your freq at that time, it will
> be close.

Tnx for the reply Mike. I have no problem getting the actual Doppler value
at any time during the orbit, what I would like to know is what the true
beacon frequency is, and how much it varies in its space environment. This
is more for technical curiosity reasons than operational ones, I can still
get on and make the contacts regardless.

Backing out the doppler, I see a variation of +-10kHz or so over many
orbits. How much of that is due to my converter and how much from the bird?
If it is mostly at my end I will put a PTC on my xtal, but having damaged
xtals in other rigs by doing this I would rather not do so if it wouldn't
make a significant difference.

At some point I will finish off my GPS-locked frequency reference project
and will be able to make these measurements myself. I was hoping someone out
there already had that capability and could provide some data.

73  Alf  NU8I
Scottsdale AZ DM43an

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