[amsat-bb] Re: station setup

Bruce Robertson broberts at mta.ca
Sun Apr 29 06:24:54 PDT 2007

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.

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.

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 :-)

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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