I understand some carrier current stations use "leaky coax" . I even read that at some drive in theaters, the owners use wires underneath the ground to broadcast the signal to the customer's on their car radios.
I understand some carrier current stations use "leaky coax" . I even read that at some drive in theaters, the owners use wires underneath the ground to broadcast the signal to the customer's on their car radios.
My thought is, if someone had a large property...could it/would it - be possible to bury this "leaky coax" or "wires" under the ground say along a trail, pathway or driveway for say a mile or two and still be legal as a part 15 station? Or would this only apply to educational facilities and drive ins?
Then perhaps within 20 feet of the wire/"leaky coax" one would be able to pick up the signal along the mile or two path.
Has anyone tried this?
Would a part 15 signal be too weak?
Would it come under rules of a carrier current station?
How would a buried mile long radiator/leaky coax be legal for Part 15?
Your thoughts?
You ask a good question and you are going to receive a lot of answers which are just opinions.
Here's mine:
First, are we talking about AM or FM. It may not matter since the part 15 rules allow for operation on both bands based on a maximum field strength at a specified distance from the INTENTIONAL RADIATOR.
If one considers the leaky coax to be the intentional radiator then it seems to me that if you meet the field strength limits in the vicinity of the radiator (leaky coax) then it should not matter how long it is.
My OPINION is that if you meet the field strength at a distance requirement with leaky coax, then you may be compliant.
By the way, there is nothing special about leaky coax. Some is designed for a controlled and specified leakage but RG58/U has only about a 78% shield and leaks signals like crazy from my experience. This would not be a bad choice for experimenting.
A practical consideration is the necessity of measuring the field strength to verify compliance, but that is a topic for another thread.
Neil
You ask a good question and you are going to receive a lot of answers which are just opinions.
Here's mine:
First, are we talking about AM or FM. It may not matter since the part 15 rules allow for operation on both bands based on a maximum field strength at a specified distance from the INTENTIONAL RADIATOR.
Neil
I am talking AM and looking at possibilities as covering a certain area whether it be a path a mile or two long, or perhaps much further if someone had the money and the man power to bury the wire several miles along a road.
This could mean anyone driving along within 20 feet of the road would pickup the signal. I use this as a possibility as the drive in theater concept as a example.
How about a buried wire along a county road, a buried wire along a pathway, a buried wire from your property to throughout your subdivision or neighborhood ( assuming if you got permission from all concerned).
So how much power would it take to cover a mile or two using buried wire? 100 milliwatts? Or several watts? If a college campus is using electrical lines to transmit a signal within the building.
Would not then a buried wire work for quite a long distance too along the path of the wire? And the signal should be steady along the path of the wire which would make this even more ideal for covering a couple of acres or miles with no fading or interference.
Now for the questions...
So is it legal?
How much power would be involved?
Is one restricted to "leaky coax"?
Can one use a buried single insulated wire instead?
Is this now a carrier current station?
A part 15 station?
Would this be less expensive than several transmitters?
I'll add this in here, this would not be for everyone. But it could be yet another option one could consider without having to buy extra transmitters and trying to keep them all synchronized. If this legal, it is definately worth experimenting with.
I found info about AM leaky cable. Walt Disney World uses leaky cable on AM. It costs $12,000 for a mile of cable. It was used in the World Fair in 1939. Found a fairly good page about leaky cable.
http://www.radioedu.com/RG%20Articles/DEC-2003.pdf
My guess is burying an antenna is like burying a flashlight and then try to see it. 🙂
WDCX AM1610 Part 15
John
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