Dwayne Reid
2018-06-19 02:08:22 UTC
Good day to all.
One of the people with whom I work regularly wants to use analog
Motorola base radios as an extension of the Intercom systems that I
work with. We normally use a GPIO line from the Intercom system to
control transmitter PTT but we now have an application where VOX is preferred.
Some of the Motorola radios we have available are capable of both
digital and analog transmission. These already have a short audio
delay of somewhat less than 100ms which does work well. However, for
various reasons, the radios that we want to use in this particular
project are analog-only and do not have an audio delay available.
What the audio delay does is ensure that the first word of a
transmission that is triggered by VOX is not lost. That is: the
person begins to speak, the radio is immediately put into YX mode,
then the delayed audio is fed to the transmitter. This allows the
entire beginning of the transmission to be heard by the recipients
without losing the first word or two.
I used to build something like this many years ago, using Reticon
bucket-brigade delay chips. Those have now vanished.
The easiest solution for me is to simply find something that is
available off-the-shelf at reasonably-low cost. Barring that, modern
PIC chips have enough RAM to buffer 100ms of audio at a reasonable sample rate.
Two questions:
1) Is anyone aware of a readily-available audio delay module at
reasonable cost? I just need the bare PCB since this module would be
incorporated with the remaining electronics needed.
2) Is anyone aware of a pre-existing PIC project that I can clone /
modify as needed for my needs? I would prefer a minimum of external
components: use both the on-board A/D and either PWM or DAC to
reconstruct the output audio.
Unbalanced audio for both input and output, audio level not critical,
prefer 10 bit or 12 bit resolution simply to maximize the available
dynamic range. Frequency response up to 5 KHz (or higher) preferred
- the communications radios are already pretty brutal and I don't
want to degrade that further with the delay circuit.
If there is a suitable PIC design, I'd prefer to work with the PIC16F
family as opposed to the PIC18F. However, I'll take what ever is available.
Many thanks!
dwayne
--
Dwayne Reid <***@planet.eon.net>
Trinity Electronics Systems Ltd Edmonton, AB, CANADA
780-489-3199 voice 780-487-6397 fax 888-489-3199 Toll Free
www.trinity-electronics.com
Custom Electronics Design and Manufacturing
One of the people with whom I work regularly wants to use analog
Motorola base radios as an extension of the Intercom systems that I
work with. We normally use a GPIO line from the Intercom system to
control transmitter PTT but we now have an application where VOX is preferred.
Some of the Motorola radios we have available are capable of both
digital and analog transmission. These already have a short audio
delay of somewhat less than 100ms which does work well. However, for
various reasons, the radios that we want to use in this particular
project are analog-only and do not have an audio delay available.
What the audio delay does is ensure that the first word of a
transmission that is triggered by VOX is not lost. That is: the
person begins to speak, the radio is immediately put into YX mode,
then the delayed audio is fed to the transmitter. This allows the
entire beginning of the transmission to be heard by the recipients
without losing the first word or two.
I used to build something like this many years ago, using Reticon
bucket-brigade delay chips. Those have now vanished.
The easiest solution for me is to simply find something that is
available off-the-shelf at reasonably-low cost. Barring that, modern
PIC chips have enough RAM to buffer 100ms of audio at a reasonable sample rate.
Two questions:
1) Is anyone aware of a readily-available audio delay module at
reasonable cost? I just need the bare PCB since this module would be
incorporated with the remaining electronics needed.
2) Is anyone aware of a pre-existing PIC project that I can clone /
modify as needed for my needs? I would prefer a minimum of external
components: use both the on-board A/D and either PWM or DAC to
reconstruct the output audio.
Unbalanced audio for both input and output, audio level not critical,
prefer 10 bit or 12 bit resolution simply to maximize the available
dynamic range. Frequency response up to 5 KHz (or higher) preferred
- the communications radios are already pretty brutal and I don't
want to degrade that further with the delay circuit.
If there is a suitable PIC design, I'd prefer to work with the PIC16F
family as opposed to the PIC18F. However, I'll take what ever is available.
Many thanks!
dwayne
--
Dwayne Reid <***@planet.eon.net>
Trinity Electronics Systems Ltd Edmonton, AB, CANADA
780-489-3199 voice 780-487-6397 fax 888-489-3199 Toll Free
www.trinity-electronics.com
Custom Electronics Design and Manufacturing
--
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