[amsat-bb] Re: station setup

Eric Fort eric.fort at gmail.com
Sun Apr 29 13:05:49 PDT 2007

On 4/29/07, Bruce Robertson <broberts at mta.ca> wrote:
> Quoting "Simon Brown (HB9DRV)" <simon at hb9drv.ch>:
> > ----- Original Message -----
> > From: "Eric Fort" <eric.fort at gmail.com>
> > >
> > > What are the advantages and disadvantages of computer control for
> > doppler
> > > shift and tracking?  is computer control of these parameters  good
> > enough
> > > that  2 stations could ragchew on ssb without manual intervention?
> > >
> >
> > Properly implemented, computer control will provide:
> >
> > * Rotator control,
> > * Full Doppler correction.
> >
> > And yes - you can rag-chew without turning too many dials but currently
> > with
> > FO-29 'resting' you'll only be able to use VO-52 and get up to 10-15
> > minutes
> > quality time on a pass. (You shouldn't hog an FM-only satellite such as
> >
> > AO-51 or SO-50.)
> >
> > P3E will be a different matter, you'll be able to talk for hours when
> > it's
> > visible.
> >
> > Simon HB9DRV
> >
> There's also AO-7, a satellite with a higher orbit and therefore longer
> potential QSO time, about double that of VO-52. However, AO-7 needs to be
> in the sun to work and its mode is somewhat unpredictable. In the near
> future we will have Delfi C3 and Kiwisat added to the stable.
> Full computer-aided doppler tuning only permits 'hands-free' operation
> when
> *both* stations have it perfectly implemented. If I'm talking to you and
> my
> computer clock is off by 10 seconds, you will need to tune a bit during
> our
> conversation, and so will I. Mind you, this isn't nearly as much as in
> other circumstances. In case you are thinking that this might be easy to
> do
> remotely, I should add that such 'hands-free' QSOs are, in my experience,
> quite rare.

actually, I'm asking about tuning and tracking by computer because I'm
thinking eventual voice SATGATE  for a linked remote base system I'm
working to develop.  It would be really nice to just put the radio on link,
find a place on the transponder (or maybe just park it somewhere in the
passband and remote users get to courtously wait) and talk (just another
link from the users perspective, except for  possibly finding where in the
link passband to occupy.  on that note has anyone tried using a stable pilot
tone on ssb to use as a reference for auto tuning ssb, or possibly using one
of the beacons on the satelite as a known reference for the same purpose?
if not it would be an interesting technical persuit for current and future
birds.  having 2 stations with the exact same time (even to microseconds or
better) is not such the challenge anymore that it once was (gps anyone).

If I may respond in general to the spirit of the original letter, I would
> say that current satellites do not really present an excellent opportunity
> for extended conversations. I certainly don't want to characterize this
> aspect of the hobby on behalf of everyone, but I think for many the fun
> generally resides in the combination of improving one's technical
> proficiency (with which this list and the publications from AMSAT help
> greatly) and rather briefly meeting others who are on the same path. That
> said, I very much enjoy the company of the people I meet on the birds;
> like
> QRP HF, these short contacts that overcome technical challenges can be
> very
> satisfying. If the idea of communicating with someone else via a device
> hurtling through space enthralls you, then it's worth it.
> As Simon explains, all this will change with the launch of P3E, ESEO and
> Eagle, the coming high-orbit satellites.

I'm in this for the technical proficency as well.  I'm mainly asking about
capability and possibility at this point and look forward to that growing in
the future with the comming launches.

For now, if your space is limited, you might consider going portable and
> buying or making an Arrow-type antenna. Combined with a full-duplex HT
> such
> as the TH-D7A, this lets you work the FM birds from any spot. In general,
> as Simon notes, this isn't for ragchewing; however, those of us north of
> 45
> deg. know the fun of chatting on AO-51 as it passes over the Arctic Circle
> :-)

Do absolutely all the sats for voice (ssb) work require pointable antennas?
If I'm going to go portable then mobile would seem even better.   For the FM
birds I hear my ft-8900 should be able to do that...but what antenna for
either?  in my initial post I was mainly contrasting between pointable and
non pointable antennas.

Also the what else do I need part got snipped.  anyone for addressing that
part, is the ft-847 and antennas everything I need or should I also have a
few preamps and transverters in the mix?

73, Eric

It's delightful to see this increase in interest in the birds. This is a
> great time to get involved in AMSAT: there are so many exciting launches
> in
> the next three years!
> 73, Bruce

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