1. Home
  2. Hobby Electronics Basics
  3. Mux / demux on wireless audio

Mux / demux on wireless audio

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
Reply to
Douglas Beeson
Loading thread data ...

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
Reply to
Tim Wescott

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.

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

thanks, Tim

--
Douglas Beeson
Reply to
Douglas Beeson
[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?
Reply to
Jack

I have already:

kHz audio, 2 channels on each of two bands. The transmitter takes line-lev el audio and uses the 5.8 GHz range (scientific or public band, I think) to transmit.

two bands selected by the transmitter.

n sending very low-frequency, inaudible signals in the range 1-20 Hz. As th e 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.

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 0-2

0 Hz signals onto the carriers using AM or FM or whatever modulation scheme is easiest. Then decode and demodulate at the receiving end.

nd some money, but the electronics have to be doable by an intermediate-lev el guy ;-)

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.

Reply to
George Herold

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
Reply to
Douglas Beeson

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
Reply to
Tim Wescott

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

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.

--
  \_(?)_
Reply to
Jasen Betts

ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.