Originally posted by Carl over at the locked/blocked/no access section:
It is well documented that a lengthy ground wire connecting an elevated transmitter to earth exceeds the 3-meter limit imposed by 15.219, and all schemes to circumvent this problem with lightning arresters or toroids have doubtful benefits.
There are two solutions being presented for consideration.
Solution # 1 is to convert the transmitter ground to an infra red beam and shoot it to the earth where an infra red receiver converts the ground to a very low impedance and connects direct to a ground rod and buried radials. A second infra red beam from earth to transmitter would provide the return path for the ground;
Solution # 2 is to do much the same thing but with a fiber optic path from transmitter to earth. Fiber optical cable is a two-way medium and would provide the 2-direction pathway.
This original post is copied over from the ALPB board to which no one can reply to unless a member. This subject should be here in the public access area and not tucked away in such manner as to prevent open discussion on a subject that involves everyone and not just specific membership of some organization.
My response as follows.
Unfortunately both ideas above will not work. A fiber optic cable or infrared light beam is not a conductive object like metal or a wire. RF needs a conductive medium, for both a resonator or return path.
Now what might work is the "Spout Antenna" approach, where a stream of water is shot through an inductive coil at the base, and the antenna is in effect the water stream shooting upward. The same concept might work in the reverse, where a stream of water is shooting down to the ground and a capture/recycle pan. The pan, being conductive, would have the physical connection to the Earth dirt, forming the return pathway for the RF and elevated 3 meter antenna.
RFB
Since I've been in involved in Part 15, I've been throwing all my trash, compost and other debris into what has become a huge pile. My neighbors have now joined in and are also adding to the pile. I figure by the end of next summer, the pile will be about 50 feet high; high enough to install my transmitter and short ground lead on top and finally get a decent coverage.
PerryNH I think raising the level of an area of earth is an interesting solution to adding several feet of height to an AM antenna without running afoul of the radiating vertical ground lead.
My own mulch pile is not very large in diameter, but does raise the average terrain at one location by about four feet.
Possibly some landscape techniques could be applied by way of supporting block containments to raise a particular area to even greater heights while blending it into the overall skyline.
The objective, if attainable, would be to have the antenna looking at a downward angle toward the target area.
"I've been throwing all my trash, compost and other debris into what has become a huge pile."
Great approach and no different from installing a ground mounted 15.219 system on a hill.
Make your own little mountain. Just want to make sure there is nothing in that pile that ends up creating a stink, or objection to others in the immediate surrounding. The way things are these days, some gripe over someone enjoying a BBQ in their own backyard because the wind carries the grill smoke through their open window.
RFB
Around here you need a permit for landscaping if the average height of the surrounding terrain is to be altered more than a few feet.
I only know that digging requires a permit in this location for safety reasons, but am not sure whether raising the terrain would also require a permit.
Naturally good drainage characteristics would need to be engineered into a change in ground level, and that might be the main reason for needing a permit.
Building a 70-foot cliff might interesting to do, but being ordered to take it down might spoil the adventure.