Idea.
Wish to mount the Part 15 transmitter in a weather proof box in a small room underneath a porch. This will keep the transmitter available for easy approach and adjustment from indoors.
Idea.
Wish to mount the Part 15 transmitter in a weather proof box in a small room underneath a porch. This will keep the transmitter available for easy approach and adjustment from indoors.
Wish to mount the ten-foot pipe antenna on a tripod tower located outdoors about 30-feet from the porch. Obviously the contact between transmitter and pipe antenna could not be done with ordinary lead-in or coax because the Rules specifically disallow such length.
However it seems to me that a 1:1 fiber optic method would allow the transmitter output to reach the antenna without violating the rules.
Elsewhere on this website the only related reference to such an idea is found here
part15.us/files.p15/LPBcarriercurrentdesigntechnote2.doc
LPB describes using fiber optic for RF distribution in a carrier current system.
Comments are welcome.
Fiber Optic Link
Interesting idea. I presume the antenna end of the FO will need some electronics and this will now be the “final amplifier” to which the 100 mW limit applies. Also, any power leads to the FO receiver will radiate unless decoupled. Don’t know how this plays according to part 15 though.
I have thought about a similar thing using a home brew copy of the final stage of the SSTRAN and CAT5 cable as the line. I have some differential balanced line driver/receiver ICs which should, with decoupling of the audio, gnd. and power, prevent radiation from the CAT5. The connections to the SSTRAN would be for audio, RF, and power. It’s on my back burner right now but maybe sometime later…..
Neil
Following Through
Thanks Neil for your thoughts on the fiber optic idea. Allow me to discuss some thoughts that continue from what you’ve said.
When I specified a 1:1 relationship I envisioned delivering the output of the part 15 transmitter intact, not increased, not decreased. Let’s assume the output of the transmitter is only 50% efficient. It would therefore be 50-milliwatts and would be a carbon copy of the actual transmitter final, avoiding all the downfalls of using a lead-in wire. In this way it would be exactly the same result as having the transmitter mounted at the antenna.
Also, questions of ground and power line radiation hold true in any case, unless special engineering is employed to avoid or filter, but that problem exists either way.
Your idea of mounting a final stage remote from the transmitter is detailed in publications found on this website, including Ernest G. Wilson’s Carrier-Current Techniques, wherein he describes driving a coaxial cable with whatever number of watts are required, 1-watt or 5-watts, etc., and terminating these at “repeaters,” essentially part 15 final stages with 100-milliwatts adjustable at the input to the final. He even gives schematics for achieving this.
In fact my fiber optics idea is a way of doing almost the same thing but with only one part 15 transmitter.
Light ain’t radio
Hi Carl,
Your idea can work but you have to have an optical converter/transmitter on the pickup end, and the reverse on the other end, i.e., you must convert the radio signal to a light signal, then back again at the antenna. Such a device might exist, but I’ve never seen one … very specialized, probably pricey. Further, there can be no sharp bends in the optical cable, only gradual bends.
Actually I found a few
Actually I found a few related articles, but all the devices involved are highly specialized, and most of them seem to indicate what you describe, i.e., converting the audio to RF and amplifying the signal, then converting it to optical, sending it to the antenna site and converting it back to RF at the site, and setting the amplification to whatever the license calls for. All the applicable gear I’ve seen thus far is for professional Satellite/CATV applications, and the prices of the gear are definitely not for hobbyists, unless you’re wealthy enough to have such ‘toys’ 😉
In your scenario, the optical to RF modulator and amp would have to be adjusted to 100 mw.
Boeing Surplus, which actually no longer exists, used to have miles of optical cable and transmitters/receivers and boosters. Maybe there are some similar surplus dealers around with similar parts.
Good luck 😉
Viewed as Audio
If the light/signal converters were sufficiently wideband it may be that 1.68 mHz might pass through as if it were audio.
Possibly, but again, we’re
Possibly, but again, we’re talking about specialized stuff. I’m still looking myself because of the same interests … but I haven’t seen anything other than very expensive gear. You’d be pretty much on your own to come up with anything, but that’s part of the fun 😉
Nice Experiment
I found this kit. This would stop those nasty rf’s gettin’ back into your stuff.. LOL
Use two for stereo?
http://www.electronickits.com/kit/complete/fibe/ck1502.htm
http://www.electronickits.com/kit/complete/fibe/ck1502.pdf
Nice Experiment
I found this kit. This would stop those nasty rf’s gettin’ back into your stuff.. LOL
http://www.electronickits.com/kit/complete/fibe/ck1502.htm
Kits and Products
The optic fiber kit looks really interesting. I couldn’t find mention of its frequency bandwidth, but maybe it could be modified to allow sending the 1.68mHz RF signal.
Let me also ask about these items from the Markertek catalog (markertek.com)
Kramer Composite Video to Fiber
KR-611T Transmitter $168 / KR-611R Receiver $168
Beamer Composite Video Fiber System
VS1010 Complete Transmit/Receive $369
Is it not true that video base band means DC to 10 mHz bandwidth, or there about?
for power use a small solar
for power use a small solar panel charging a sealed backup battery.
no long electrically conductive runs to ground at all.
Complete Isolation
Yes, Re. Chrysafis, being totally isolated from all conductive connections would make this an ideal laboratory situation.
This is an experimental project I think is worth trying.