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Old 6th November 2012, 11:24 PM   #51
freax is offline freax  Australia
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thats exactly what I was thinking, a 1mhz carrier.

and no you won't receive any flack.
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Old 6th November 2012, 11:26 PM   #52
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Funny thing I just found that circuit, I have changes the zenner to two 55V neons in series with a 39 k resistor to give a nice voltage drop of 105V, this allows me nice headroom for the 270V output required for my preamp. Also going to use a 6x4 rectifier before this stage via 1.4H choke just for the hell of it. see how this goes....... Ive heard the argument between regulated supplies and unregulated, my question is if the final reservoir cap is large enough for the application then why not just use regulated?
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Old 6th November 2012, 11:28 PM   #53
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Quote:
Originally Posted by HJWeedon View Post
Hi you guys.

Please get real. There is no way of sending amplitude modulated Audio over a fiber optical link. The laser diode is grossly non linear and would result in distorted output. In my opinion a better way would be to frequency modulate the laser-light as on off pulses with variable pulse repetition rates. This modulator could work at perhaps a center-frequency of about 1MHz and a FM deviation of perhaps 200kHz.

Then we have to have a frequency demodulator circuit at the transmitter end within a feedback loop to correct any distortion in the transmitter modulator.

At the receiving end there has to be an identical demodulating circuit that without feedback which should mimic the transmitter Audio input.

I have never done this so I have no idea what trouble I would be in.

Just a thought that is all, I am sure to receive a whole lot of "flack" for this idea.

Hans J Weedon.
Just think something this unique will have very little chances of being being hacked by a third party....
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Old 6th November 2012, 11:36 PM   #54
TV7 is offline TV7  Australia
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Originally Posted by freax View Post
thats exactly what I was thinking, a 1mhz carrier.

and no you won't receive any flack.
It sounds like GAY, a gay musical.....
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Old 7th November 2012, 05:54 AM   #55
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Hi.

Just thinking out loud.
I am a professional circuit designer with a somewhat decent reputation. If you guys are willing to participate at the professional level, together we can design a state of the art optical transmission link. This link would have to meet modern Audio specifications.
As a goal we should set a dynamic spec of at least 70dB instantaneous signal to noise ratio, with about 120dB total dynamic range. The allowable harmonic distortion level should be about 0.01% and the frequency response about 15Hz to 23kHz +/-1db..

If you do not know what these specs mean, the way I see it, is that the no input noise should be 120dB below full scale output, but it is allowed that the noise and distortion increases as the signal grows so that at full scale output the in band noise and distortion can increase by 50dB. The reason I want to spec a channel performance this peculiar way is that the human hearing mechanism has an instantaneous dynamic range of about 50dB, and we should be about 20dB better than the hearing mechanism.

In reality you can just not perceive a signal which is 50dB below a simultaneous loud signal. The loud signal totally overwhelms the acoustical transducer in your ear so that it can not respond to a small signal in the presence of a loud signal.

Comments please!

Hans J Weedon.
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Old 7th November 2012, 06:15 AM   #56
freax is offline freax  Australia
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Sounds good to me, but suggest that we consider shifting the carrier frequency to something thats a little higher than 1Mhz, something like 98MHz.

There is another reason for this too, at 1Mhz there is far less chance of a leak in one of these devices when they are out into the field and in use of splattering all over the shortwave band with harmonics up the wazoo, where it could potentially travel much farther than if a leak had occured on the FM BCB.

Ontop of that developers/designers can troubleshoot and shield their oscillators with a simple FM radio.

And at 98Mhz we can borrow/copy ideas or schematics from tried and tested tube/transistor FM BCB oscillators/receivers (And TV tubes will have a use again.) and simply increase the FM deviation to ungodly large amounts.

As you say, an FM deviation of 200kHz is fine, but I bet that will soon quickly grow to a much larger and broad use of the allocated spectrum as the quality of the link is increased, I doubt we will ever get anywhere very far though with plastic fiber (ie, TOSLINK).

At least that way by upping the carrier we can use simple little amplifier chips like the ERA-5 wideband RF amplifier to amplify our signals, and hopefully develop some kind of ultra-wideband modulator circuit using nothing but industry standard components.

And components will be much smaller too, shortening signal paths, reducing the chances of coupling, enabling much more elaborate shielding to be put into place, even allowing the use of modules to be installed/retrofitted into a cramped vinyl TT box, maybe even someday being placed upon a TT's arm and powered from a bias power supply, straight to the source!.

This will keep the SACD/Vinyl audio crowd happy, what with a fully analog FM modulated wideband optical transport, potentially capable of transporting their entire discs information over to the amplifier/preamp, is optically isolated, and isn't digital!.
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Last edited by freax; 7th November 2012 at 06:41 AM.
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Old 7th November 2012, 06:51 AM   #57
TV7 is offline TV7  Australia
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Quote:
Originally Posted by HJWeedon View Post
Hi.

Just thinking out loud.
I am a professional circuit designer with a somewhat decent reputation. If you guys are willing to participate at the professional level, together we can design a state of the art optical transmission link. This link would have to meet modern Audio specifications.
As a goal we should set a dynamic spec of at least 70dB instantaneous signal to noise ratio, with about 120dB total dynamic range. The allowable harmonic distortion level should be about 0.01% and the frequency response about 15Hz to 23kHz +/-1db..

If you do not know what these specs mean, the way I see it, is that the no input noise should be 120dB below full scale output, but it is allowed that the noise and distortion increases as the signal grows so that at full scale output the in band noise and distortion can increase by 50dB. The reason I want to spec a channel performance this peculiar way is that the human hearing mechanism has an instantaneous dynamic range of about 50dB, and we should be about 20dB better than the hearing mechanism.

In reality you can just not perceive a signal which is 50dB below a simultaneous loud signal. The loud signal totally overwhelms the acoustical transducer in your ear so that it can not respond to a small signal in the presence of a loud signal.

Comments please!

Hans J Weedon.
I'd love to Hans, this sort of thing is right up my alley. Reminds me of the sort of R + D you used to get in magazines like Electronics Australia. A shame they are no more. Unfortunately I have a very busy schedule at the moment and cannot participate in earnest. However I suggest you start a new thread with the groundwork if members are prepared to start.
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Old 7th November 2012, 07:21 AM   #58
freax is offline freax  Australia
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I've made another thread over at Analog Line Level

Here: A new fully analog FM modulated wideband optical transport Open Standard.
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