Fiber optics and attenuation

[shortride]

Could fiber optic cable be used to improve a received signal instead of using a copper media in coax? The receiver circuitry probably would not be compatible with a fiber optic signal huh?

[jackj]

Fiber optic cable is used to transmit light, not electricity.

[shortride]

Originally Posted by jackj

Fiber optic cable is used to transmit light, not electricity.

Purhaps I should have used a different word rather than electrical.

The light media used in fiber optics can transmit radio signals. The light is the media whereas copper wire is the media for receivers and transceivers. Fiber optics is already transmitting telephone communications along with data for other applications.

I think I amswered my own question here. http://www.eham.net/articles/1981

[RadioDaze]

Fiber optic cables can transmit digitized information, by carrying modulated light. They can't transmit "radio signals" per se, which are analog and in a different spectrum than the fiber is able to carry. You would need the information contained in the radio signal to be digitized and then use that data to modulate the light. Then reverse the process at the other end. No actual radio frequency energy would pass along the fiber.

[prcguy]

You can buy RF to light converters and place a fiber light transmitter at the antenna, fiber it to your remote receiver and feed the receiver with a light to RF converter. I use them in my work but they are made for specific purposes like carrying L-band output of satellite LNBs to remote receivers.

They work fine for their intended applications but do not have enough dynamic range to handle every signal an antenna would pick up plus their noise figure is lousy and would limit the weaker signals.
prcguy

[n5ims]

Originally Posted by shortride

Could fiber optic cable be used to improve a received signal instead of using a copper media in coax? The receiver circuitry probably would not be compatible with a fiber optic signal huh?

What problem are you trying to fix? There are probably much better and cheaper ways to fix that problem.

If you are simply trying to reduce the loss in the coax, you can simply purchase some more expensive coax that has lower loss numbers than what you're currently using. Even some heliax would be less than the very expensive RF-to-Fiber and Fiber-to-RF converters (you'd need at least one for each end obviously) would cost.

If you think that the fiber optic cable would shield you from a lightning strike, think again. All that electronics you'll need at the antenna will require power and that strike would simply flow down the power wires instead.

If you just want to be "cool", by using fiber while everyone else uses coax, try something else. How about putting your scanner up by the antenna and having it controlled by a computer. You use another computer (or even your iPhone) to communicate with that controller computer to control your scanner.

While there are some RF over Fiber solutions out there, they are quite expensive and designed for very specific tasks. They probably wouldn't do much at all for the wide frequency range and varied needs of a scanner listener.

[shortride]

Originally Posted by RadioDaze

Fiber optic cables can transmit digitized information, by carrying modulated light. They can't transmit "radio signals" per se, which are analog and in a different spectrum than the fiber is able to carry. You would need the information contained in the radio signal to be digitized and then use that data to modulate the light. Then reverse the process at the other end. No actual radio frequency energy would pass along the fiber.

I'm nobody to argue because I know nothing about this stuff. But If what I am reading is correct and if I understand what I'm reading, RF analog can be transmitted by optic fiber (OF). Please correct me if I read it incorrectly. http://www.rfsolutions.com/fo-rf1.htm

[MikeOxlong]

Nope, you're correct. We use RF to Fiber in a Distributed Antenna System.

Hope you've got lots of money. It's not cheap and definitely not worth it for the average scanner user.

[jackj]

You will also have a problem if you want to transmit on your new fiber optic antenna system. You can't, at least not with any appreciable power.

[W2NJS]

Some years ago I sold a two-camera CCTV system to a boat yard. One camera was placed on the top of the main building on a weather-resistant PTZ mount, and the other camera was placed in a lounge/locker room building about a quarter of a mile away. The remote camera was connected to a baseband-to-fiber converter with a fiber-to-baseband converter at the monitor in the main building, and the roof camera was connected to the monitor via piece of high-quality RG-59 coax that ran, as I recall, about 200 feet. The point of this description is to say that the fiber video signal was much better than the signal coming from the roof, and I had known that would be the result I would have sold them fiber for both video runs. I can't recall the costs of the converters but it certainly was not out of line.

[MikeOxlong]

Originally Posted by jackj

You will also have a problem if you want to transmit on your new fiber optic antenna system. You can't, at least not with any appreciable power.

Sure you can. The fiber is handling light not rf. You can dump in whatever rf power level the converter will take, transmit it to the converter at the other end using enough light to reach the far end and than convert it back to rf using whatever rf power amplifier you want.

[RadioDaze]

Originally Posted by shortride

I'm nobody to argue because I know nothing about this stuff. But If what I am reading is correct and if I understand what I'm reading, RF analog can be transmitted by optic fiber (OF). Please correct me if I read it incorrectly. http://www.rfsolutions.com/fo-rf1.htm

Well, this is all news to me. I'm always willing to stand corrected. (Unless I can sit.)

[mmckenna]

Yeah, do a search on DAS, or Distributed Antenna Systems. We use them at work also. The cell carriers hand off a padded down RF feed to our system that transports the RF (TX and RX) over a single strand of single mode fiber out to various sites. At those sites is a unit that takes the fiber input, AC power and gives an RF output to the antennas. They run about 30 watts on the TX side. Nice low profile solution for cellular coverage.
Not sure how wide band they can be. All of ours are dedicated to specific blocks of cellular spectrum. Each carrier has their own at each site. Some have more than one for different bands.

Not even close to a reasonable solution for a hobbyist. It would be an expensive solution, WAY more than new coaxial cable.

[shortride]

Please don't think for a moment I'm considering this. I'm so poor I can't pay attention. I wouldn't be here now if I had not inherited my R7100 receiver.

Thanks for all of the input.

[mmckenna]

I understand, most of us have been there. Honestly, though, some of the best radio equipment I have I got for free. Sometimes that's the way it works. Make friends and ask around. Sometimes you can get stuff just by being in the right place at the right time and asking nicely.
I scored about 100 feet of 1/2 inch heliax many years ago. A contractor was running it in our building for cable TV. I looked at it and pointed out to them they were running 50 ohm coax for a 75 ohm system. They kind of blew me off but did leave me with the left over length that was on the reel when they were done pulling.
Of course a week later they were back replacing it all with the correct 75 ohm stuff.

The RG-6 quad shield the cable TV and Satellite installers use is pretty good stuff. Sometime you can get left over reel ends for free just for asking. RG-11 is out there, but not as popular. Sometimes you can get that stuff out of old buildings. Even the .500 or .750 hard line the cable TV ariel runs use can be had for free now that a lot of it is going to fiber. Even though it's 75 ohms, it'll work just fine for receiving. If you ever decide to transmit with it, building matching transformers is pretty easy to match it to a 50 ohm transmitter.
Also, don't over look building stuff yourself.