This idea was talked about a few years back but faded from attention. The idea is to use fiber optic link to send the output from an indoor AMT3000 transmitter to an outdoor loading coil/ 3-meter stick.
http://www.electronickits.com/kit/complete/fibe/ck1502.pdf
Step one, the input to the fiber-optic transmitter will be modified to accept the estimated 60mW RF output from the AMT3000 transmitter. As we know, medium wave frequencies are relatively close to the top of the audio spectrum, so this should not be a problem. The RF would therefore be sent on the fiber, which in this kit is 14-feet.
Step two, received and converted from optical back to waveform, the signal will pass through the modified receiver/amplifier circuit, which has a volume control and can be adjusted for 100mW to the final amplifier stage of the optics receiver and coupled to the loading coil/ 3-meter stick and to ground radials.
Such a system would not violate any section of the rules for Part 15 AM medium wave because it would not constitute a “lead-in wire.” The advantage would be in keeping the AMT3000 safely indoors.
The line is open for comments.
Analysis
So what would be needed is an RF to Optical/Optical to RF wavelength converter.
RFB
Do You Mean
I think you (RFB) are suggesting that the existing audio to optical transmitter would not be capable of converting an RF frequency to optical?
Are you saying this existing amplifier would be entirely replaced by the device you mentioned? (RF to optical converter)
What about at the other end of the fiber. Could the existing receiver/amplifier be capable of conversion back to RF, or would we need something different at that end also?
Perhaps this kit isn’t needed at all…… perhaps we need other devices to do this?
If that’s true, I take it that you believe the idea is possible…. one way or the other…???
Existing A/O converter
“I think you (RFB) are suggesting that the existing audio to optical transmitter would not be capable of converting an RF frequency to optical?”
Yep.
The audible range of the EM spectrum maxes out around 25Khz for human beings, lower for some, maybe a tad higher for others. But WELL below the radio frequency part of the EM spectrum.
Now what could be done is take the RF signal and feed that into a fiber optic IR emitter so that the IR emitter is switching at the RF frequency rate and sending the IR pulses down the fiber optic line.
To re-convert, an IR detector picks up the IR pulsed light at the radio frequency rate and feeds that into a switch such as a transistor or FET and that switches at the RF frequency rate, re-generating the original generated RF frequency to feed to the antenna.
RFB
Big Argument Breaks Out
Human hearing isn’t what I’m talking about.
What I’m talking about is electronic amplifier “hearing.” An electronic “audio” amplifier can have dog-like “ears” and “hear” frequencies up in the MegaHerz range….depending on components.
IR (infra red) just means “below visible light,” but that’s WAY WAY above medium wave radio frequencies.
Either way should work, unless I’m missing something in translation from English to English.
Answering Your Own Confusion
“What I’m talking about is electronic amplifier “hearing.” An electronic “audio” amplifier can have dog-like “ears” and “hear” frequencies up in the MegaHerz range….depending on components.”
Well an amplifier is an amplifier is an amplifier. What separates them is what they are designed to amplify. An audio frequency, an RF frequency, a light frequency..and so on.
Yes indeed IR is WAY WAY WAY up there in frequency..perfect for it being a main carrier through a fiber cable for a sub carrier to ride on.
And yep..it all depends on components in each type of amplifier that determines what that amplifier will do.
Since your wanting to eliminate the “conductive” aspect of having the TX indoors and its antenna outdoors, how else would the RF get from the TX to the antenna without some vehicle for it to get there?
RFB
Anther RF/O-O/RF Conversion
Another method would be to use the same IR emitter and detector via fiber cable approach but instead of pulsing the IR beam at the RF frequency rate, pulse it at a much higher frequency rate so that MW frequencies can “ride” on the IR beam like a sub carrier rides on an FM carrier..aka “SCA”.
Many wireless headphones back some years ago used IR emitter/receiver designs. Sony had them on a bunch of their high end consumer TV’s.
The MW sub carrier could then be envelope detected and fed into a linear final meeting the limit. Since there is no coax…who knows.
RFB
Example
Though the design would be more complex for this subject the following link will show an example of modulating an IR beam with audio frequencies.
http://www.circuitstoday.com/simple-ir-audio-link
Replace “audio in” and “audio out” in the schematics with “RF in” and “RF out”.
Now here is an even better example of using an RF/IR-IR/RF link.
http://www.rentron.com/NEW_IR_TO_RF.htm
What ya think?
RFB
That’s What I Mean
Ya, RFB, that’s the thing I mean.
And I’m guessing these “through the air” IR transmission methods could be easily adapted to “through the fiber.”
This idea is on a roll.
Somebody build something.
Let me know.
Either Or
“And I’m guessing these “through the air” IR transmission methods could be easily adapted to “through the fiber”.”
Why not either through the air or through a fiber cable?
Though the fiber cable would be better protection for the light beam along with keeping the emitter and detector from becoming blocked by dirt/dust etc.
I worked for a Sony Service Center in Odessa Tx for several years back in the 90’s and collected a good number of service manuals to a variety of Sony TV’s. I have a service manual around here somewhere to a Sony XBR set which has the IR headset system. It used an IR array above the CRT to transmit the tv’s audio to the headset which had IR detectors to pick up the signals. Stereo audio to boot as well.
Little Sony inside joke we techs had in the Sony Service network…XBR = eXtra Bucks Required. 😀
It used IR beams and injected sub carrier frequencies onto the IR beam at 1.6 and 1.8 Mhz, one for each channel of audio. The audio was FM modulated onto the sub carriers.
Set up a similar device at the TX indoors, except instead of using regular IR diodes, use a fiber optic IR emitter injected with the MW frequency sub carrier AM modulated.
Then at the tail end, a fiber optic IR detector feeding a sub carrier detector which extracts that sub carrier frequency and feeds that to a linear amplifier of 100mW and then on to the antenna.
The tail end would be similar to the IR headset receiver with the exception that we wont demodulate the received sub carrier, but instead extract it, filter it and then pass that RF carrier on into a 100mW linear final.
Bye bye coax! Of course there would still need to be power ran out to the outdoor antenna for powering the outdoor IR receiver module and 100mW linear final. But no need for running the second pair for audio.
I had tossed the idea out here and in other forums about creating a new type of Part 15 AM transmitter system where the “guts” of the TX were indoors and the 100mW final would be outdoors at the antenna. Fiber cable was one idea and another was a twisted pair pulsed with TTL logic at the RF carrier frequency rate.
Granted such a system, fiber or other would present its own set of difficulties to overcome. But I believe it can work by taking already proven designs of similar systems and adapting them to this task.
Think of it as an IR beam version of a microwave STL link with base band injected modulation and sub carrier injection. Same exact concept, only instead of an RF link, its a light link.
RFB
Very Worth Doing
What you have shown, RF, is that my starting idea at the beginning of this thread, is just one of many possible ways of keeping the main transmitter indoors and the RF output part outdoors.
This idea is so interesting someone has got to do it as a super science experiment.
Maybe I’ll try…. somebody should.
Glad to know it’s possible.
Creative Juices
“This idea is so interesting someone has got to do it as a super science experiment.”
The only limitation is one’s imagination..or self imposed limits of going beyond the edge of the piece of paper.
Imagination is what brought us all these neat things we take for granted today. The Wright brothers first flight, Edison’s bulb, Tesla’s AC, and on and on.
Just because we live in a “modern” world filled with amazing devices does not mean that imagination and creativity is no longer viable or worthwhile. Even when mankind reaches to the point of traveling in space at faster than light speeds and defies gravity..does not mean the creativeness and exploration for new ideas becomes outdated.
RFB
Example
Here is a fine example of just such a IR device.
http://www.smithgear.com/mdrif240rk.html
It’s a Sony!
This unit uses the same design as did the XBR tv sets that came with the IR headset system for private listening. IR beams with injected RF sub carriers for left and right full fidelity audio.
The headset is equipped with the sub carrier detectors and demodulator. The base unit sends out the IR beams along with the sub carriers riding on those beams to the headset.
They used RF sub carriers because the frequency response for the audio is far better than it would be modulating the IR beam directly with audio. The result is full fidelity audio.
RFB