[Space] Audio

Greg Stramback grog at piratelabs.com
Fri Mar 19 10:58:12 PDT 2010


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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