I've realized that doing things concering increasing power is not the best choice is too risky. the only reason I wanted to increase power in the first place is because I live in a very rural community and my closest neighbor within line of sight lives about 4/10 mile from where I do. I'm now trying to focus on improving grounding. Is there any limits that can keep me from having an unlimited amou
I've realized that doing things concering increasing power is not the best choice is too risky. the only reason I wanted to increase power in the first place is because I live in a very rural community and my closest neighbor within line of sight lives about 4/10 mile from where I do. I'm now trying to focus on improving grounding. Is there any limits that can keep me from having an unlimited amount of copper grounds?
In answer to your question about ground limits, my answer is no. The part 15 rules do not specify nor limit ground radials.
There is a point of diminishing return on the ground radials that you install. I am not wise enough nor experienced enough to give you guidance on this and I hope others who have the experience can comment. Get advice before spending $$$ and time on grounding.
Neil
First and foremost, copper is expensive. So using just the right number of radials just long enough is the key. The objective: to lower the ground resistance in your antenna system. Rule of thumb for "very short" antenna systems, is to limit the length of the radials to the physical length of the antenna. My Rangemaster is in the clear at 30 feet. I run a single 12 awg ground to a chemical ground rod with 20-20-foot long 14 awg ground radials buried around the base of the mast. Range: approx. 1 1/2 miles. So that's 32 feet of 12 awg wire, 400 feet or so of 14 awg and a ground rod. At 15 cents a foot, thats about 65-75 dollars in a ground system. Unless you have some junk housewire laying around, that is about as cheap as you can do it.
People, a lot smarter than me, have determined there is a point where putting more copper in the ground does NOT produce anymore significant improvement. It is better to have many short radials than a few long radials.
Marshall Johnson, Sr.
Rhema Radio - The Word In Worship
http://www.rhemaradio.org
It has been stated a few times here that a properly designed ground radial system does not radiate signal; i.e. symetrical, opposing, horizontal radials. The problem with elevated antennas being the extended grounding lead to the RF ground becomes part of the radiating antenna.
Also, it's been stated here that for very short transmitting antennas (Part 15 AM) several radials of the same length as the antenna usually perform better than a few very long radials.
My question then, has anyone here experimented with a ground plane antenna consisting of a 3 meter vertical and four or six ground plane radials of 3 meter length. It should be easy to construct and mechanically strong enough to use as an elevated antenna with ground plane radials. This would be similar to the CB ground plane antenna of years gone by (with proper loading coil included to resonate.)
I'm sure someone will point out that any conductor leading to an earth ground for safety purposes would radiate but perhaps some type of RF choke (ferrite bead balun?) at the antenna grounding connection could prevent that while allowing static charges to dissipate. That would keep the RF at the antenna and elevated ground plane and off of the safety ground.
A very sensible post, mram1500.
I've done some NEC modeling about this, and will post further on this topic tomorrow? when I have time to put it together.
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That would be great! I appreciate your taking time to post that info.
When I get the time and money, I'm going to build the antenna as a ground plane with six 3 meter radials and one 3 meter vertical. It will be interesting to compare the performance of ground mounted to elevated.
Since short antennas have such a high angle of radiation, maybe I'll mount it sideways and see if its directional characteristics would improve coverage into one area.
Since short antennas have such a high angle of radiation, maybe I'll mount it sideways and see if its directional characteristics would improve coverage into one area.
But the shape of the radiation pattern from a 3-meter medium-wave vertical isn't much different than from one that is 1/4-wave high. This is easy to see in the pattern comparisons shown on page 3 of the paper at this link:
http://filebay1.home.comcast.net/Elevated_Part_15_AM_Antennas.pdf
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