[App_rpt-users] usbfobs

[David McGough]

Hi Bob,

VOX can be done to generate the RX COS signal, but, it isn't ideal at
all--I've tried it. The list of reasons is long, below is a quick from my 
experience.

The circuit in QST is designed to provide PTT from a computer-generated
digital signal, and it should work well for that. Remember that when the
radio should be transmitting, MODEM audio from the computer is continuous
and roughly constant in peak level. Once the computer MODEM transmission
is complete, the output level drops to virtually zero, with very little
audio noise of any kind from the computer.  This scenario is ideal for
VOX--a single, predictable keying threshold set-point and a very short
no-signal cut off delay.

Audio from an FM receiver is different. It has many complications for
trying to use VOX to generate COS. First, you'll need a more complex
circuit that implements both an adjustable unkey delay (remember: human
voice isn't constant) and input level set-point, which may be complicated
to adjust due to various noises coming from the RX.  So, at best, you'll
likely end up with a customized solution that works only with a signal FM
radio without tweaking all the settings again and again. Then, another
issue is that you may loose the first syllable of audio at key-up, while
the VOX activates.

As I said, VOX can be done for casual use. But, with the effort involved 
to get VOX to work, just put that same effort into making a real COS 
circuit!

73, David KB4FXC


On Sat, 28 May 2016 k5mvz at verizon.net wrote:

> What about VOX control for PTT?  See page 67 in June 2016 QST.  But it still uses an ext. USB sound adapter.
> 
> de-
> Bob
> K5MVZ
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> -----Original Message-----
> From: Skyler F <electricity440 at gmail.com>
> To: app_rpt-users <app_rpt-users at ohnosec.org>
> Sent: Fri, May 27, 2016 8:07 pm
> Subject: Re: [App_rpt-users] usbfobs
> 
> 
> 
> It seems easy to use GPIO as an output to toggle the Transmitter, but I can't figure out how I would use the GPIO on the pi as an input for COR if I am using speaker audio
> 
> 
> On Fri, May 27, 2016 at 7:00 PM, Steve Wright <info at meshnetworks.co.nz> wrote:
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>           
>     yeah
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> On 28/05/16 12:47, Skyler F wrote:
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> even better GPIO on the pi
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>         
> On Fri, May 27, 2016 at 6:46 PM, Steve          Wright <info at meshnetworks.co.nz>          wrote:
>           
> 
>             I think we're on the wrong track with our fixation on cmedia            hackable chipsets.  It's too hard.
>             
>             Why can't we use one of the other DSP modules and some            serial USB _TX signalling?
>               
>               
>               
>               On 28/05/16 04:00, Sam Skolfield <kj6qfs at gmail.com> wrote:
>               
>                 Please share any findings with the group, many of us are                looking for them
>                 too...
>                 
>                 On Thu, May 26, 2016 at 9:17 PM, Steve Wright <info at meshnetworks.co.nz>
>                 wrote:
>                 
>                 
>                   Does anyone have a reliable source of modifiable USB                  audio devices?
>                   
>                   It's really really difficult to find hackable ones                  without buying one here
>                   and there...
>                   
>                 
>               
>               
>                         
>               
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>         -- 
>         
>           
> Skyler Fennell            
> amsatnet.info
>             
> KDØWHB
>             
> electricity440 at gmail.com
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