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Post by Boomer on Aug 3, 2017 6:22:11 GMT
I think that trees and other objects absorb the most RF if they're close to the transmitting antenna, but as you get farther away, objects matter progressively less.
I don't have the exact figures, but if the trees are 100 feet away, they won't matter much, that's in the transmitter's far field. At that distance it wouldn't matter if the receiver was surrounded by trees either, the character of the signal should be like other stations at that distance and farther out.
You'll note that AM broadcast stations with big towers keep the fields around their stations cut flat. With short 3 meter antennas I think it's even more important to have the nearby area clear, since the antenna is being run at a high impedance.
My dad was annoyed by my antennas when I was experimenting, and I had an idea of having a loaded vertical in the woods to have it out of the way and be stealth. Sounds great, but now I know it would have been a bad idea because of the absorption, all trees on a slope.
Boomer
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Post by mighty1650 on Aug 3, 2017 11:41:26 GMT
You'll note that AM broadcast stations with big towers keep the fields around their stations cut flat. With short 3 meter antennas I think it's even more important to have the nearby area clear, since the antenna is being run at a high impedance. This is more or less because of the destructive nature Tree Roots would have on the ground system, plus a clear field would allow for easier repairs. Trees definitely have an impact on part 15 signal strength but not as much as you'd think, my Rangemaster was less than 30 feet away from some seriously huge trees and my coverage was phenomenal. Unless the antenna was physically in the tree or touching the tree you probably won't have much of an issue but I'd still avoid putting the transmitter too close to the tree if possible.
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Post by thelegacy on Aug 3, 2017 15:10:27 GMT
I knew FM is effected by trees. This is why height equals might with FM. AM however from my experience does NOT like metal anywhere around the receive antenna. Try listening while you go under a bridge or overpass and your reception is null. I know Rock and concrete seem to effect AM too. Id say get your TX on top of a hill if possible.
Remember Berry in Ky and his issues when he set up a P15 AM station and even his FM was effected by his surroundings. You could try a TX outside first and find the position where you get the best signal. Then take the TX back in before it rains lol and then set up your install there. Living with someone who doesn't like the sight of antennas can be an issue as AM antennas are quite noticeable especially if your dealing with a huge coil in the center.
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Post by End80 on Aug 3, 2017 15:39:25 GMT
I never considered AM antennas to be very noticeable at all. At least not the standard whip most use, however I agree those with a huge coil would probally catch yurt eye.
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Post by Boomer on Aug 8, 2017 9:25:06 GMT
The whip is about the same size as a CB quarterwave, so some people probably relate it to that, though there are fewer CB base antennas on roofs now.
You could attach a CB groundplane to the bottom to disguise it, or use something that looks like a Yagi TV antenna as a ground plane, with the transmitter box and whip above it.
Antennas have changed character over the years, and now you have compact antennas for digital TV, wi-fi, and satellite TV dishes. Maybe an AM transmitter with whip can be mounted behind a satellite dish, the box hidden from view from the street or neighbors, and the whip coming up from behind, and coil back there if it has an external coil. It gets tougher if you have a capacity hat or a radial ground though.
We want to get Carl back on track and safe from witch hunts!
Boomer
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Post by Deleted on Aug 8, 2017 13:56:55 GMT
Old Memories New Again
Boomer triggers a fond memory: "We want to get Carl back on track and safe from witch hunts!"
I think I was hunted by a witch several years ago!
I met a woman who said she and her mother are witches and she belonged to a Witches Meetup Group that has a huge Costume Ball on Halloween. She borrowed my Ramsey FM25B Transmitter and moved away overnight without leaving a new address!
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Post by Boomer on Aug 8, 2017 21:04:36 GMT
Those sound more like gypsy witches. You could have told them that to hire my transmitter, you have to hire me also, and you would have been their DJ. They still might have changed you into a toad and walked off with the transmitter.
If you want it so that from all appearances outside that there's no radio station, carrier-current can do it, it's very stealth Part-15. If you mounted your station in the basement by the electrical box, people could visit your living areas and never even know.
Boomer
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