Unfortunately the horse rolled over, said something about radio waves not going over the horizon. So I was obliged to whip it - whip into shape.
Radio wave propagation is called "Skip". The radio waves skip off certain layers of the atmosphere depending on their frequency. It is not uncommon to have reception close, lose reception for some distance, and again achieve reception at some greater4 distance.
Look up "Radio wave propagation".
Look up "Radio wave propagation".
Whip it good....
As the frequency of the radiated RF increases, it behaves more and more like light.
HF frequencies like AM radio in the .5 to 1.7 MHz range will follow a surface, especially water, and the ground wave will go much further than line of sight dictates. In the 60's and 70's there were two stations with their towers IN the Atlantic ocean water (actually Biscayne Bay) off Miami Florida. WQAM (560 KHZ and WIOD (610 KHZ) could be received most anywhere in Florida as long as you were a few miles from the water. Their towers were moved inland during a "cleanup the bay campaign."
VHF frequencies (FM radio and some TV) will follow a surface to some degree. They are also susceptible to "edge diffraction." This is how we can get some TV and FM radio down in the "holler" we live in, surrounded by ridges and hills about 200 feet above us.
UHF and above behave more light like, especially above 1GHz. As with light, microwaves and even UHF TV, will bounce off reflective surfaces. Any flat metal works, and ham radio operators including myself, have successfully bounced signals off the ISS. Doppler shift is the big impediment to making real communications work off the ISS. ISS visibility lasts for 10 minutes or so max. The ISS is coming at you at high speed, so reflected RF is shifted up in frequency. As it passes overhead, or tangential to your position, the RF frequency shift is zero, then as the ISS is moving away from you the reflected frequency begins to drop.
Speaking of the ISS, if you believe it really exists, you can see it pass by about an hour after local sunset, since it's not in the shadow of the earth yet. Look up the flyover paths on the NASA web site, pick a time when it passes nearly overhead about an hour after local sunset. Times vary due to local conditions, an hour worked well in flat south Florida. As it passes over heading east, it will suddenly vanish from view since it falls into the shadow of the earth. Some Iridium satellites do the same thing. I suppose a math whiz could use info from a couple of passes to calculate, say the diameter of a sphere........
When I lived in South Carolina in the 70s, I used to be able to get WOWO Fort Wayne Indiana on AM 1190 almost 650 miles away. We could only get it starting at dusk until about 10 pm, maybe 11pm in the middle of the summer.
In fact you whipped my fists with your face so hard that I had to massage them afterwards
Well Jim, if you are going to claim that radio waves are blocked by the horizon, and thus ships can't get them without a tall antenna, what do you expect? You'll have to have better arguments than that. That works for light, and some of the higher radio frequencies, as George points out. But radio? Come on.
My star gazer app on my phones shows me when it's passing by. We watched it go over several times in Kona. Sucker moves fast!
Pano,
We are going to try the laser experiment. Do you have a good link you want to share for the easiest method with good accuracy. I was reading somewhere to use a lake but not longer than 3 miles. Put the laser off the ground and measure it from the top of the water. The hardest part seems to be to get the laser flat. I don't think a level is good enough? How the heck can I level it with good accuracy?
We are going to try the laser experiment. Do you have a good link you want to share for the easiest method with good accuracy. I was reading somewhere to use a lake but not longer than 3 miles. Put the laser off the ground and measure it from the top of the water. The hardest part seems to be to get the laser flat. I don't think a level is good enough? How the heck can I level it with good accuracy?
VHF rado is mainly line of sight, UHF more so. This simple picture is complicated by a litte refraction under normal conditions, and the occasional appearance of ducts over sea paths. Normal propagation assumes a radius of curvature about 4/3 times the actual (alleged) earth radius. On a flat earth the signal would go much further.Pano said:
The flatists do need to explain why TV transmitters need to be put on tall towers or hills yet still only reach maybe 50 miles before the signal quickly declines beyond that point. It cannot be attenuation due to the air because that would give a much flatter attenuation curve, and would affect long-distance aircraft communication too.
Okay here is something to think about. I get in my airplane and fly from Auburn to Sea Ranch 130 SM (200 Km). I level off and set power and trim for 2000 meters high. How come my altitude doesn't increase over time?
Am I really trimmed for level or for a curved flight path? Maybe the earth is flat.
Am I really trimmed for level or for a curved flight path? Maybe the earth is flat.
How would it make a difference? 2000m above ground is the same either way. And having your own plane is just showing off. 😛
I think major cause of the problem is that people go everywhere by airplane! If you used a bicycle, not even for a moment you would think Earth is flat😀
- Status
- Not open for further replies.