[Space] aprs

grog at piratelabs.com grog at piratelabs.com
Mon Feb 22 21:33:34 PST 2010


Nils... you're worried about a dead carrier after the packet is transmitted?  Why?

-g-

Gregory Stramback
grog at pirate.org




On Feb 22, 2010, at 9:08 PM, nils at shkoo.com wrote:

> I did not yet attempt to get the vox mode working on the pg777.  It works on my vx8r fine.
> 
> It'd be nice to detect existing transmissions, but I'm not sure how effective it'd be.  They're pretty short, so the 0.5 second minimum vox delay that I have on the vx8r means that there's a big window for the race condition.  I don't know if the vox delay is less on the pg777.
> 
> I guess the other way to do it would be to have an external signal detector that activates the PTT; I think you should just need a diode, a resistor, a capacitor, and a transistor.  (The values of which would have to be worked out)
> 
> See attached for a screenshot of me driving over the bay bridge hitting my transmit button every couple minutes. :)  (or http://aprs.fi/?call=KF7FWZ-3 if you get to it before it expires)
> 
> I would really prefer to figure out some way to activate the PTT without having to wait for the VOX to kick in, and having to transmit a period of dead-air afterwards.
> 
> -nils
> 
> On Mon, 22 Feb 2010, Mikolaj Habryn wrote:
> 
>> 2-way communication does open some possibilities, but nothing that I
>> think we'll be ready to use for the next launch. Getting a solid
>> downlink is going to be much more useful in the short term - and you
>> should let the list know about this, too; I suspect people will be
>> interested.
>> 
>> Oh, and I take it vox mode (?) on the radio works as advertised?
>> 
>> (another stray thought - rather than doing full decode of incoming,
>> you could maybe just FFT a few milliseconds of audio to look for 1200
>> baud tones to detect in-progress transmissions?)
>> 
>> m.
>> 
>> On Mon, Feb 22, 2010 at 10:03 AM,  <nils at shkoo.com> wrote:
>>> Yes.  Here's the aprs specification if you're interested:
>>> 
>>> http://www.aprs.org/doc/APRS101.PDF
>>> 
>>> The '@' format that I got working is the easy-to-encode one. :)
>>> 
>>> I'm now working on encoding using the "mic-e" format now which is
>>> significantly shorter.  It's a real pain to encode, but it increases the
>>> chances of successful transmission if the communications channel is iffy.
>>> 
>>> The hardware is probably capable of receiving packets too.  Let me know if
>>> you can think of any really good uses for that and maybe I'll work on
>>> implementating that half too.
>>> 
>>> -nils
>>> 
>>> On Mon, 22 Feb 2010, Mikolaj Habryn wrote:
>>> 
>>>> That's seriously fantastic :) Congratulations! I take it you can send
>>>> arbitrary packet types?
>>>> 
>>>> m.
>>>> 
>>>> On Sun, Feb 21, 2010 at 11:40 PM,  <nils at shkoo.com> wrote:
>>>>> 
>>>>> Rock on:
>>>>> 
>>>>> http://aprs.fi/?c=raw&limit=&call=KF7FWZ-3
>>>>> 
>>>>> I apparently wasn't sending enough gard data after the packet and it
>>>>> wasn't
>>>>> all making it out or something.  I'll fine tune it later I guess
>>>>> 
>>> 
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