[Space] Audio

nils at shkoo.com nils at shkoo.com
Fri Mar 19 11:24:21 PDT 2010


Do you have a reference for "COR"? I think that's what I'm talking about 
but my google fu is weak right now.

But yes, with the right software support the G1 could pretty easily detect 
the opentracker signal and use it to tell when not to transmit.  I don't 
think I'll be able to do that in time for the launch but I think that it's 
possible.

-nils

On Fri, 19 Mar 2010, Greg Stramback wrote:

> are you talking about VOX activation or do you actually have something
> similar to COR that would control the transmitter?
>
> -g-
>
> On Fri, Mar 19, 2010 at 10:56 AM, Albert Alexander <
> albert.alexander at gmail.com> wrote:
>
>> Can we feed the opentracker signal into the G1 mic jack and use it as a
>> trigger?
>>
>>
>> On Fri, Mar 19, 2010 at 10:43 AM, Greg Stramback <grog at piratelabs.com>wrote:
>>
>>> Good point Nils.  It's kind of a shame we don't have the weight allowance
>>> that would allow for a centralized GPS based timing platform that could
>>> synchronize the clocks.  Eh, weight alone wouldn't be the problem anyways.
>>>  The expense is nothing to sneeze at.
>>>
>>> Besides, we're only using one device's data as a reference to compare the
>>> other with.  A reference packet every 4 mins will fit in nicely with the
>>> regular 30sec interval packet.
>>>
>>> -g-
>>>
>>> On Fri, Mar 19, 2010 at 8:51 AM, <nils at shkoo.com> wrote:
>>>
>>>> I think it'll be tough to avoid them interfering with each other except
>>>> if
>>>> we have some kind of synchronization mechanism.
>>>>
>>>> I think that if we try to configure the clocks to be at the same rate,
>>>> we'll get pretty close but not exact. Then when they start interfering
>>>> with each other it will take longer for them to stop.
>>>>
>>>> I think the best thing to do would be to set the intervals as follows:
>>>>
>>>> opentracker: 31 seconds
>>>>
>>>> g1: 127 seconds
>>>>
>>>> Guestimating the transmit time as 1 second, that way they will only line
>>>> up on the same second once every 3937 seconds, so most of the beacons
>>>> should be fine even if the timing isn't exact.
>>>>
>>>> If we tried to line them up on 30 seconds and it ended up with the
>>>> following intervals:
>>>>
>>>> opentracker: 30 seconds
>>>> g1: 30.1 seconds
>>>>
>>>> Then when they line up, they would transmit on the same second for 10
>>>> beacons in a row, so we could lose a whole 5 minutes of transmitted data.
>>>>
>>>> Ideally, the thing to do would be to make them able to listen to telle
>>>> when the other is transmitting. I'm pretty sure the opentracker can do
>>>> collision avoidance of some sort, but the android code not so much right
>>>> now.
>>>>
>>>> -nils
>>>>
>>>> On Thu, 18 Mar 2010, Albert Alexander wrote:
>>>>
>>>>> Sounds right to me, but I'll defer to Nils. I know they do not transmit
>>>>> simultaneously.
>>>>>
>>>>> On Thu, Mar 18, 2010 at 8:44 PM, Christie Dudley <longobord at gmail.com
>>>>> wrote:
>>>>>
>>>>>> I think the idea we had was that they were each sending at the same
>>>>>> interval.  If they maintain even reasonably good clocks and aren't
>>>> aligned,
>>>>>> they shouldn't ever overlap.  I think their duty cycle is low enough
>>>> that
>>>>>> this wouldn't be a problem.
>>>>>>
>>>>>> (I'm assuming that you mean amateur radio, not an actual
>>>> walkie-talkie,
>>>>>> here?)
>>>>>>
>>>>>> Christie
>>>>>> _______
>>>>>> "We also briefly discussed having officers replaced by very small
>>>> shell
>>>>>> scripts." -- Noisebridge meeting notes 2008-06-17
>>>>>>
>>>>>> The outer bounds is only the beginning.
>>>>>> http://www.flickr.com/photos/genriel/sets/72157623376093724/
>>>>>>
>>>>>>
>>>>>> On Thu, Mar 18, 2010 at 6:24 PM, Albert Alexander <
>>>>>> albert.alexander at gmail.com> wrote:
>>>>>>
>>>>>>> Nope, they transmit at separate times. We could use a fet to switch
>>>>>>> sources but that's more parts and wires.
>>>>>>>
>>>>>>>
>>>>>>> On Thu, Mar 18, 2010 at 6:10 PM, Greg Stramback <grog at piratelabs.com
>>>>> wrote:
>>>>>>>
>>>>>>>> I'm making the assumption that we're expecting a certain percentage
>>>> of
>>>>>>>> garbled / unreadable packets due to two audio sources being
>>>> combined?
>>>>>>>>
>>>>>>>> -g-
>>>>>>>>
>>>>>>>> On Thu, Mar 18, 2010 at 5:56 PM, Albert Alexander <
>>>>>>>> albert.alexander at gmail.com> wrote:
>>>>>>>>
>>>>>>>>> The walkie-talkie is getting audio from two sources. I suggested
>>>> using a
>>>>>>>>> splitter to combine the sources, but this will load down the output
>>>>>>>>> transistors unless we add two resistors in series before the
>>>> splitter. 10k
>>>>>>>>> is fine. This will attenuate the current of each signal. We could
>>>> use a
>>>>>>>>> summing amp if we want to avoid the attenuation, or we could just
>>>> turn up
>>>>>>>>> the volume.
>>>>>>>>>
>>>>>>>>> Will test G1 audio out AC coupling tonight after 5moF
>>>>>>>>>
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>>>>>>>>>
>>>>>>>>
>>>>>>>
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>>>>>>
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>


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