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New Design Technology

I am thinking about creating a new design for transceiving audio over a range of a couple of meters. The criteria are as follows:

  1. Up to four audio sources each of which must hear all of the other three stations. (Headset-microphone-earphone) Although I'm not ruling out any scheme, what I think would work is a "base station" that could be mounted somewhere in the vehicle, receive up to four separate frequencies, and retransmit the detected audio over a common transmit channel.

  1. Fairly high electromagnetic intensity environment ... tens of watts of RF at 120-140 MHz. at a meter or so range. Hundreds of peak power watts (average 5 watts or so) at 1 GHz. also at a meter or so.

  2. Entirely possible that in some instances the device will have to operate in direct sunlight. I'd prefer not to use opto techniques.

  1. Whatever the technology and power source, the device will have to be worn on the head for several hours at a time. It may be possible to mount the device on the chair the person is sitting on but I'd like to keep my option open to mount the whole works inside the individual headset.

  2. Moderately high noise environment made a little more liveable by the use of noise-cancelling microphones.

  1. If at all possible, I'd like something that will work in an amateur radio band...the device will only be marketed with proof of amateur license.

2 meters might work, as would 220 or 440. 220 is so quiet that I'd really like to operate in that band if possible.

I'm not so much looking at a design per se, but more a technology or device(s) that I could research and see what is available and preferable. Comments appreciated.

Jim

Reply to
RST Engineering (jw)
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I was thinking about a system wherein all car drivers within line-of-sight would be able to converse, sort of full duplex CB. The social evolution of that would sure be interesting. I figured it would be RF or optical. Preferably received sound level would not vary with distance, at least until the range limit was hit.

I was thinking that everybody would transmit random carrier-modulated pulses, with pulse density carrying the audio modulation. The receiver is then just a limiting bandpass amp, a comparator, optional one-shot, and a lowpass filter.

You could also do some fancy digitized burst packet things, I guess, with overlapped packets straddling each group of samples, so collisions could be mostly corrected for. More work.

John

Reply to
John Larkin

Nordic semi has some stuff, such as nRF24Z1, but not exactly suitable, it might give you some ideas

martin

Reply to
martin griffith

I like the idea, very much. If you can get it to work then good luck. I think you could be on to a winner.

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Gibbo

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Reply to
Gibbo

Bluetooth does this (with digital audio) in the ISM band at 2.45G. There are probably appnotes out there for the phone/headset sides of a BT link, eg:

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Seems like the GHz range has size advantages for that, even if you want to homebrew.

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Ben Jackson AD7GD

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Reply to
Ben Jackson

AFAIR Ham radio is not allowed to be operated just like that. To be part 97 compliant each transmitter would have to have its own frequency and each user would have to have multiple (or multichannel) receivers. Some "900 MHz" ISM band radios can do this directly. Moreover, you should consider motorcycle usage as well. Range should be about 100 m line-of-sight at the standard 1 W.

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 JosephKK
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Reply to
joseph2k

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