[Date Prev][Date Next][Thread Prev][Thread Next] - [Date Index][Thread Index][Author Index]

Re: mobile satellite operation...



Hi Bruce ad Mark,

Howard's (G6LVB) Tracker 2 has the floating point code (using a PIC 18F620) 
and uses the Plan 13 and the Predict code to calculate the pass information. 
He has a stub for CW output.  The choice of the 4 MHz crystal obviously 
effects how valid the data is after a few days of service.

I have had a Tracker 2 running for months and been talking with Howard about 
some upgrades and combining features.  His code is open source and you can 
download it from his web site.
I understand that some of the code is a little compiler dependent on timing 
accuracy.

This new uC will fit in the same LVB Tracker board and can be programmed via 
a real serial port on the board. I recommend this as a good place to work 
from.

It was designed to be run from a battery as a handheld unit.

73,
Gould, WA4SXM

----- Original Message ----- 
From: "Bruce Robertson" <ve9qrp@gmail.com>
To: "Mark VandeWettering" <kf6kyi@gmail.com>
Cc: "Amsat-Bb" <amsat-bb@amsat.org>
Sent: Thursday, July 24, 2008 7:46 PM
Subject: [amsat-bb] Re: mobile satellite operation...


> On Wed, Jul 23, 2008 at 6:18 PM, Mark VandeWettering <kf6kyi@gmail.com> 
> wrote:
>>
>> During one of the many recent discussions, somebody mentioned that
>> Doppler tracking wasn't really that difficult, all one needed to do was
>> download InstantTrack or whatever on some old, ancient PC, and that you
>> would need to have a PC around to track the satellite anyway.
>>
>> But here's the thing: I _don't_ need a pc to track the sats. I operate
>> handheld with my little TH-D7A in one hand, and my trusty Arrow in the
>> other. Before each pass, I run a little Python satellite prediction
>> program that I wrote to dump information about the pass, which looks 
>> like:
>>
>> AO-51 will be visible from grid CM87ux starting in 04:44:31 at 01:44:03
>> 01:44:03 +0.0 132.0 K 18.8N 102.4W AOS
>> 01:45:00 +3.3 127.9 K 22.3N 103.2W
>> 01:46:00 +7.2 122.4 K 25.9N 104.0W
>> 01:47:00 +11.4 114.8 K 29.5N 104.9W
>> 01:48:00 +15.8 104.4  33.1N 105.9W
>> 01:49:00 +19.8 90.3  36.7N 106.9W
>> 01:50:00 +22.1 72.7  40.3N 108.0W
>> 01:50:18 +22.3 67.1 J 41.4N 108.3W MAX
>> 01:51:00 +21.5 54.1 J 43.9N 109.2W
>> 01:52:00 +18.3 37.9 J 47.5N 110.5W
>> 01:53:00 +14.1 25.5 J 51.1N 112.0W
>> 01:54:00 +9.7 16.5  54.6N 113.6W
>> 01:55:00 +5.7 10.0  58.2N 115.6W
>> 01:56:00 +2.0 5.2  61.7N 117.9W
>> 01:56:35 +0.1 2.9  63.7N 119.4W LOS
>>
>> At home, I know basically where the compass points line up, and for away
>> from home contacts, I carry a little compass. With a tiny bit of
>> practice and a reasonably accurate digital watch, you get pretty good at
>> just tracking the antenna naturally over the course of a pass. With the
>> FM birds, I just listen for the signal getting raspy, and tune down in
>> frquency as needed.
>>
>> For me, I don't want to carry a PC. Or a laptop. I have my little FT-817
>> that's actually pretty good to use on a strap around my neck, but if you
>> have to sling a laptop and operate it all simultaneously, you're
>> probably screwed.
>>
>> So, here's the idea: the Python library I wrote is actually pretty
>> simple. It's a direct port of G3RUH's Plan 13 algorithm, and runs fast
>> enough to be entirely useful. It also has the capability of doing
>> Doppler translations at a reasonable rate, even on a fairly modest
>> microcontroller. (In fact, the way I started on this project was noting
>> that G6LVB's tracker implements the same algorithm to provide automatic
>> antenna tracking). So, why not build a little battery powered
>> microcontroller unit that provides Doppler tracking for the FT-817ND?
>> You could load the orbital elements onto (say) and SD card on your PC in
>> the house, and then jam the little thing into a smallish battery powered
>> microcontroller, and it would provide automatic Doppler tuning. Then,
>> truly mobile operation would be possible on the linear birds, without
>> having to bring laptops or juggle with the reasonably fast Doppler of 
>> VO-52.
>>
>> Yes, the setup isn't quite ideal: you don't get full duplex, but in most
>> other respects, it would be totally adequate.
>>
>> You could even use an off the shelf controller like:
>>
>> http://gumstix.com/store/catalog/product_info.php?cPath=26&products_id=79&osCsid=cb40b0a364041ad11ee9af494c9a518f
>>
>> which has a USB->host connection, two serial ports, and costs $129. This
>> establishes a sort of greatest upper bound on how much such a project
>> need to cost.
>>
>> What do people think? Will the lack of full duplex kill me in this
>> endeavor? What am I overlooking?
>>
>> Mark "trying to turn ham radio into just button pushing" VandeWettering
>> KF6KYI
>>
>
> Mark:
>
> I've been thinking of something along these lines, too: a little pack
> that plugs into the serial port of the FT-817, powers off its aux
> power and does doppler correction using a PIC. The atmel ones have
> floating point built in at a low cost, and I have one of these
> breadboarded. Unfortunately, more pressing concerns have sidelined
> this experiment.
>
> My thinking is that the user interface would consist of a single
> button and a speaker emitting CW so that one could select the proper
> bird. It would have to have some way of connecting to a host computer
> and get updated keps.
>
> I suppose the smartest thing to do would be to build on G6LVB's code,
> but I sorta' wanted to try out the atmel chips.
>
> 73, Bruce
> VE9QRP
>
>


--------------------------------------------------------------------------------


> _______________________________________________
> Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author.
> Not an AMSAT-NA member? Join now to support the amateur satellite program!
> Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
> 

_______________________________________________
Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author.
Not an AMSAT-NA member? Join now to support the amateur satellite program!
Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb


AMSAT Top AMSAT Home