On 4/29/07, Bruce Robertson [email protected] wrote:
Quoting "Simon Brown (HB9DRV)" [email protected]:
----- Original Message ----- From: "Eric Fort" [email protected]
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 KG6KQT
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 VE9QRP