Mux / demux on wireless audio

[Douglas Beeson]

Hi all,

I'm looking for some starting direction on a new audio-art project. What I have already:

- 1 wireless audio transmitter capable of transmitting 4 channels of 2-20 kHz audio, 2 channels on each of two bands. The transmitter takes line-level audio and uses the 5.8 GHz range (scientific or public band, I think) to transmit.
- 1 wireless receiver that can receive 2 channels of audio on one of the two bands selected by the transmitter.

The transmitter and receiver support 2-20 kHz, but I am only interested in sending very low-frequency, inaudible signals in the range 1-20 Hz. As the wireless stuff is pretty expensive, I would like to squeeze many more VLF channels out of one TX-RX pair. The 1-20 Hz signals will be amplified and used to create mechanical motion.

My idea is to multiplex several very low frequency channels onto a single full audio channel. I would broadcast several "carrier" frequencies in the audio range -- say at 2.5 kHz, 5 kHz, 7.5 kHz, etc. -- then encode the 0-20 Hz signals onto the carriers using AM or FM or whatever modulation scheme is easiest. Then decode and demodulate at the receiving end.

Any thoughts on the best or easiest approach to this? I am willing to spend some money, but the electronics have to be doable by an intermediate-level guy ;-)

Thanks,
doug

--
Douglas Beeson <c.difficile@gmail.com>

 

[Tim Wescott]

On Mon, 17 Aug 2015 16:17:52 -0700, Douglas Beeson wrote:

Hi all,

I'm looking for some starting direction on a new audio-art project. What
I have already:

- 1 wireless audio transmitter capable of transmitting 4 channels of
2-20 kHz audio, 2 channels on each of two bands. The transmitter takes
line-level audio and uses the 5.8 GHz range (scientific or public band,
I think) to transmit.
- 1 wireless receiver that can receive 2 channels of audio on one of the
two bands selected by the transmitter.

The transmitter and receiver support 2-20 kHz, but I am only interested
in sending very low-frequency, inaudible signals in the range 1-20 Hz.
As the wireless stuff is pretty expensive, I would like to squeeze many
more VLF channels out of one TX-RX pair. The 1-20 Hz signals will be
amplified and used to create mechanical motion.

My idea is to multiplex several very low frequency channels onto a
single full audio channel. I would broadcast several "carrier"
frequencies in the audio range -- say at 2.5 kHz, 5 kHz, 7.5 kHz, etc.
-- then encode the 0-20 Hz signals onto the carriers using AM or FM or
whatever modulation scheme is easiest. Then decode and demodulate at the
receiving end.

Any thoughts on the best or easiest approach to this? I am willing to
spend some money, but the electronics have to be doable by an
intermediate-level guy ;-)

Thanks,
doug

To clarify: Are you going to servo several somethings to move at 1 to
20Hz? Or are you going to servo several somethings to move slower than
that, but you're planning on carrying the intelligence on the 1 to 20kHz
carrier?

I can't help but think that you'll be better served by using the
bandwidth for a 60k-baud modem, with PCM modulators fore & aft to turn
analog to digital and visa-versa.

--
www.wescottdesign.com

 

[Douglas Beeson]

On Mon, 17 Aug 2015 22:10:10 -0500
Tim Wescott <tim@seemywebsite.com> wrote:

On Mon, 17 Aug 2015 16:17:52 -0700, Douglas Beeson wrote:

Hi all,

I'm looking for some starting direction on a new audio-art project. What
I have already:

- 1 wireless audio transmitter capable of transmitting 4 channels of
2-20 kHz audio, 2 channels on each of two bands. The transmitter takes
line-level audio and uses the 5.8 GHz range (scientific or public band,
I think) to transmit.
- 1 wireless receiver that can receive 2 channels of audio on one of the
two bands selected by the transmitter.

The transmitter and receiver support 2-20 kHz, but I am only interested
in sending very low-frequency, inaudible signals in the range 1-20 Hz.
As the wireless stuff is pretty expensive, I would like to squeeze many
more VLF channels out of one TX-RX pair. The 1-20 Hz signals will be
amplified and used to create mechanical motion.

My idea is to multiplex several very low frequency channels onto a
single full audio channel. I would broadcast several "carrier"
frequencies in the audio range -- say at 2.5 kHz, 5 kHz, 7.5 kHz, etc.
-- then encode the 0-20 Hz signals onto the carriers using AM or FM or
whatever modulation scheme is easiest. Then decode and demodulate at the
receiving end.

Any thoughts on the best or easiest approach to this? I am willing to
spend some money, but the electronics have to be doable by an
intermediate-level guy ;-)

Thanks,
doug

To clarify: Are you going to servo several somethings to move at 1 to
20Hz? Or are you going to servo several somethings to move slower than
that, but you're planning on carrying the intelligence on the 1 to 20kHz
carrier?

I want several somethings driven at 1-20 Hz, downstream of the wireless receiver. The R and L channels can each carry 20kHz which I could divide into, say, 20 x 1 kHz. On each 1 kHz band I would carry a 1-20 Hz end signal.

I can't help but think that you'll be better served by using the
bandwidth for a 60k-baud modem, with PCM modulators fore & aft to turn
analog to digital and visa-versa.

So 1-20 Hz analog -> PCM -> digital -> 60 k modem -> wireless TX -> wireless Rx -> modem -> PCM -> analog 1-20 Hz?

thanks, Tim

--
www.wescottdesign.com

--
Douglas Beeson <c.difficile@gmail.com>

 

[Jack]

Douglas Beeson <c.difficile@gmail.com> wrote:

[CUT]

The real question you should ask is:
What kind of wireless transmission should I use to do "whatever you want
to do".

IMHO if you don't want to send audio signals, don't use something that
is meant to send audio signals, it will be a mess.
Depending what you want to move with the 1-20 Hz signal, probably there
are better solution than what you're thinking.

Bye Jack
--
Yoda of Borg am I! Assimilated shall you be! Futile resistance is, hmm?

 

[George Herold]

On Monday, August 17, 2015 at 7:17:57 PM UTC-4, Doug Beeson wrote:

Hi all,

I'm looking for some starting direction on a new audio-art project. What I have already:

- 1 wireless audio transmitter capable of transmitting 4 channels of 2-20 kHz audio, 2 channels on each of two bands. The transmitter takes line-level audio and uses the 5.8 GHz range (scientific or public band, I think) to transmit.
- 1 wireless receiver that can receive 2 channels of audio on one of the two bands selected by the transmitter.

The transmitter and receiver support 2-20 kHz, but I am only interested in sending very low-frequency, inaudible signals in the range 1-20 Hz. As the wireless stuff is pretty expensive, I would like to squeeze many more VLF channels out of one TX-RX pair. The 1-20 Hz signals will be amplified and used to create mechanical motion.

My idea is to multiplex several very low frequency channels onto a single full audio channel. I would broadcast several "carrier" frequencies in the audio range -- say at 2.5 kHz, 5 kHz, 7.5 kHz, etc. -- then encode the 0-20 Hz signals onto the carriers using AM or FM or whatever modulation scheme is easiest. Then decode and demodulate at the receiving end.

Any thoughts on the best or easiest approach to this? I am willing to spend some money, but the electronics have to be doable by an intermediate-level guy ;-)

Thanks,
doug

--
Douglas Beeson <c.difficile@gmail.com

How many channels do you need/ want?
What's the range?
There is the RC hobby market that you might be able to tap into
and mod for your purposes.

George H.

 

[Douglas Beeson]

On Tue, 18 Aug 2015 05:11:26 -0700 (PDT)
George Herold <gherold@teachspin.com> wrote:

On Monday, August 17, 2015 at 7:17:57 PM UTC-4, Doug Beeson wrote:
Hi all,

I'm looking for some starting direction on a new audio-art project. What I have already:

- 1 wireless audio transmitter capable of transmitting 4 channels of 2-20 kHz audio, 2 channels on each of two bands. The transmitter takes line-level audio and uses the 5.8 GHz range (scientific or public band, I think) to transmit.
- 1 wireless receiver that can receive 2 channels of audio on one of the two bands selected by the transmitter.

The transmitter and receiver support 2-20 kHz, but I am only interested in sending very low-frequency, inaudible signals in the range 1-20 Hz. As the wireless stuff is pretty expensive, I would like to squeeze many more VLF channels out of one TX-RX pair. The 1-20 Hz signals will be amplified and used to create mechanical motion.

My idea is to multiplex several very low frequency channels onto a single full audio channel. I would broadcast several "carrier" frequencies in the audio range -- say at 2.5 kHz, 5 kHz, 7.5 kHz, etc. -- then encode the 0-20 Hz signals onto the carriers using AM or FM or whatever modulation scheme is easiest. Then decode and demodulate at the receiving end.

Any thoughts on the best or easiest approach to this? I am willing to spend some money, but the electronics have to be doable by an intermediate-level guy ;-)

Thanks,
doug

--
Douglas Beeson <c.difficile@gmail.com

How many channels do you need/ want?
What's the range?
There is the RC hobby market that you might be able to tap into
and mod for your purposes.

George H.

Thanks, George. I may not have been 100% clear. I don't want to build the transmitter or receiver. I already own those. I want to build some channels of very low frequency signal, 1-20 Hz, to travel on top of the audio band that the transmitter handles. Eight channels of VLF per full audio channel would be a good start.

Tim Wescott has suggested converting all the VLF channels into digital, then using a modem to modulate / demodulate them and send over the audio line. I like that idea. What kind of modem chip or circuitry would be appropriate here?

Thanks,
doug


--
Douglas Beeson <c.difficile@gmail.com>

 

[Tim Wescott]

On Mon, 17 Aug 2015 21:53:08 -0700, Douglas Beeson wrote:

On Mon, 17 Aug 2015 22:10:10 -0500 Tim Wescott <tim@seemywebsite.com
wrote:

On Mon, 17 Aug 2015 16:17:52 -0700, Douglas Beeson wrote:

Hi all,

I'm looking for some starting direction on a new audio-art project.
What I have already:

- 1 wireless audio transmitter capable of transmitting 4 channels of
2-20 kHz audio, 2 channels on each of two bands. The transmitter
takes line-level audio and uses the 5.8 GHz range (scientific or
public band, I think) to transmit.
- 1 wireless receiver that can receive 2 channels of audio on one of
the two bands selected by the transmitter.

The transmitter and receiver support 2-20 kHz, but I am only
interested in sending very low-frequency, inaudible signals in the
range 1-20 Hz. As the wireless stuff is pretty expensive, I would
like to squeeze many more VLF channels out of one TX-RX pair. The
1-20 Hz signals will be amplified and used to create mechanical
motion.

My idea is to multiplex several very low frequency channels onto a
single full audio channel. I would broadcast several "carrier"
frequencies in the audio range -- say at 2.5 kHz, 5 kHz, 7.5 kHz,
etc. -- then encode the 0-20 Hz signals onto the carriers using AM or
FM or whatever modulation scheme is easiest. Then decode and
demodulate at the receiving end.

Any thoughts on the best or easiest approach to this? I am willing to
spend some money, but the electronics have to be doable by an
intermediate-level guy ;-)

Thanks,
doug

To clarify: Are you going to servo several somethings to move at 1 to
20Hz? Or are you going to servo several somethings to move slower than
that, but you're planning on carrying the intelligence on the 1 to
20kHz carrier?

I want several somethings driven at 1-20 Hz, downstream of the wireless
receiver. The R and L channels can each carry 20kHz which I could divide
into, say, 20 x 1 kHz. On each 1 kHz band I would carry a 1-20 Hz end
signal.


I can't help but think that you'll be better served by using the
bandwidth for a 60k-baud modem, with PCM modulators fore & aft to turn
analog to digital and visa-versa.


So 1-20 Hz analog -> PCM -> digital -> 60 k modem -> wireless TX -
wireless Rx -> modem -> PCM -> analog 1-20 Hz?

I know the latter sounds complicated, and I know that

1-20Hz analog -> mix -> wireless TX -> wireless RX -> unmix -> 1-20Hz
analog

sounds simple in theory -- but for more than just a few channels I think
you'll come out ahead to go digital. For that matter, a wireless
_digital_ link may be better yet, if you can swing it.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

 

[Jasen Betts]

On 2015-08-18, Douglas Beeson <c.difficile@gmail.com> wrote:

On Tue, 18 Aug 2015 05:11:26 -0700 (PDT)
George Herold <gherold@teachspin.com> wrote:

How many channels do you need/ want?
What's the range?
There is the RC hobby market that you might be able to tap into
and mod for your purposes.

I don't want to build the transmitter or receiver. I already own those. I want to build some channels of very low frequency signal, 1-20 Hz, to travel on top of the audio band that the transmitter handles. Eight channels of VLF per full audio channel would be a good start.

RC transmitters and receivers do most of what you want off the shelf.

Tim Wescott has suggested converting all the VLF channels into
digital, then using a modem to modulate / demodulate them and send
over the audio line. I like that idea. What kind of modem chip or
circuitry would be appropriate here?

8 channels at 1-20hz (call it 40 samples per second) and 8 say bits
precision comes out to 8x40x8 = 2560 bits per second

so a 4800 bit-per-second modem chip would be enough for that
even upto 12 bits. the problem is modems are all software these days.

off the shelf phone-line modems are going to be marginal on a
2000-20000Hz channel, phone lines are 300-3300Hz
often with one direction being 300-1700 Hz and the other being 1900-3399.

You're wanting to send data only one direction, but the modem wants
to hear the other end screaming back at it.

V.23 1200 bps in is one direction, but the frequency plan is wrong.

However your chammel is wide enough that any hokey modulation scheme that
fits in there would probably work fine at 4800 bps. eg: OOK or FSK or PSK
on a 10Khz carrier. but it's probably the sort of thing you'll need to
build from scratch. unless you can find and overclock a old modem chip.

--
\_(ツ)_