[amsat-bb] Re: Oscar 58 Pass
hartzell at gmail.com
Sat Jan 6 23:19:57 PST 2007
Your experience is typical with the current AMSATs in orbit, which are
all in a low-earth orbit, resulting in a high velocity pass, relative
to your ground station. In addition, the higher the frequency, the
greater the doppler shift.
Most regular satellite operators use PC-based software to control the
doppler shift tuning. Keplarian elements are published, which can be
used to predict the orbit and pass times, allowing for prediction of
the doppler shift.
I'm guessing most "modern" all-mode VHF/UHF rigs support
computer-control. If you want to work the sats, you really need a rig
that does full duplex, so you can hear yourself (which is sometimes
the only thing you'll hear on some of the linear transponder sats,
unfortunately!). A high-gain directional antenna also helps....
On 1/6/07, Steve Raas <sraas at optonline.net> wrote:
> Hello Everyone . I just received the Oscar-58 beacon on 437.4650 and have a
> question. I have read abt dopler shift and how It can affect radio signals
> especially with the sats. This being only the 3rd time ive ever even herd a
> sat I was shocked to note that the frequency drift was a few Hz lower on
> every cw note ( the beacon ). It reminded me of an old heathkit HF radio
> that drifted .. but never settled down. Is this about the normal expected
> Doppler Shift in a cw/ssb signal on the amsats? I was constantly turning the
> VFO ever so slightly. Or is this more on par for this particular Sat?
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