Thank you for your comments, Paul. I enjoyed reading your write-up on "the One True Rule". I notice that your stated goals were my original goals, until I really started to listen to how people used the satellites.
I'm not trying to start a trend or do anything "the right way" because if I did, it would make it harder for other stations to maintain a QSO with me. I want to take the methods used by people today, and simplify it for myself, and anybody else who would like to use my app.
You were a little hasty to shoot down the basis of the idea. If we think about it for a moment, how many people do you know with dual-band radios in their vehicle? Then think about how many people can full duplex between those bands. There are a few but most can't. My 706 can't, and that is what is driving me to write this application.
People with a shack that includes a computer and all the doo-dads won't benefit from this application. They probably can't understand why I would go to so much trouble to write such an application. They already have what they need all in one place. It's the mobile guys like me, that don't have a shack back at home with a computer interfaced radio connected to prediction software.
I have a java enabled phone, an interface cable, a 706, and it's all in my car with me when I'm operating. That's everything I need to operate a transponder sat, just like the guys at home with a PC, except my method will be a lot more lightweight. The application could use OTR, or any other method. The math is all quite simple with the assistance of Predict's GET_DOPPLER command.
I just don't see any other practical way to drive down the highway and work a Transponder satellite. You must see by now that this is the very essence of what GTO-Track will do. Only one radio is needed, with a CI-V interface and a java-enabled phone, you're in business.
As a side note, phase-2 of the project will let the user plug in key attributes (probably about 5 numbers) of an upcoming orbit, so they can work the sat without network connectivity. Even these calculations can be simplified enough to allow for a small phone to continuously tune the TX and RX freqs on the radio, or tune the TX after the user adjusts the RX.
-----Original Message----- From: Paul Williamson [mailto:kb5mu@amsat.org] Sent: Thursday, October 19, 2006 6:11 PM To: Brad, K1GTo Subject: Re: [amsat-bb] GTO-Track
In the first Phase, the application will use an internet connection to connect to a running Predict server (that's the Linux satellite tracker program). The application that runs on the phone will interface to predict to obtain Doppler shift information about the satellite currently selected, based on the QTH coordinates programmed into Predict.
That's very cute, but not really all that practical in my opinion. It would probably require less code space and a lot less battery power to just do the calculations locally, and that would work even without network coverage. The days when orbital prediction calculations could be considered CPU-intensive are long gone. The phone can still use its network connectivity to get current elements and perhaps accurate date/time if it doesn't already have that.
That was sort of question 1 there, is that how it ought to work?
Pretty much, yes.
Then the next part of the question would be: Should the application leave the RX frequency constant, not adjusting it whatsoever for any Doppler,
etc,
and only adjust the input frequency?
The long version of my thoughts on this can be found at http://www.amsat.org/amsat/features/one_true_rule.html
73 -Paul kb5mu@amsat.org
At 7:53 PM -0400 10/19/06, Brad, K1GTo wrote:
You were a little hasty to shoot down the basis of the idea. If we think about it for a moment, how many people do you know with dual-band radios in their vehicle? Then think about how many people can full duplex between those bands. There are a few but most can't. My 706 can't, and that is what is driving me to write this application.
My objection was to the proposed implementation (using a remote Predict server), not to the function.
However, now that I understand your goal I will say that I am not really in favor of it. If you run a half-duplex transceiver on an analog transponder, you will have to rely on guesses and reports from other operators to set your uplink power level. That's less than ideal. There's not a lot of range between too weak to hear and too loud, and that range is not entirely predictable. Perhaps when we have SDX-based transponders with effective alligator control, it will be OK to set your power open-loop.
Nonetheless, it's an interesting project and I wish you success.
As a side note, phase-2 of the project will let the user plug in key attributes (probably about 5 numbers) of an upcoming orbit, so they can work the sat without network connectivity. Even these calculations can be simplified enough to allow for a small phone to continuously tune the TX and RX freqs on the radio, or tune the TX after the user adjusts the RX.
I will be interested to see what you come up with along those lines. I have speculated about something similar, but never stopped to think it all the way through.
73 -Paul kb5mu@amsat.org
participants (2)
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Brad, K1GTo -
Paul Williamson