[Space] aprs

Joachim Pedersen joachimp at gmail.com
Mon Feb 22 21:33:44 PST 2010


>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
I built one of these for my vx-7r when I was playing a little bit with
digital mode stuff, circuit is slightly modified from one found on the
interwebs.
It worked pretty well, but never really found any one to talk to... I
still have it, it's a little more elaborate...
http://joachimp.fotki.com/aboutme/projects/amature-radio/keyer/
It uses the usb connector for 5V power, and otherwise just connects
inline between your signal source and your mic input. I also added a
flyback diode across the relay to keep it from misbehaving. I should
be able to bring it by sometime later this week. I'll try and also dig
up the circuit diagram...  Oh, the ic is a couple of low power
op-Amps...
-Joachim
------------------------------



On Mon, Feb 22, 2010 at 21:08,  <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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