Consider to the spec say it can be 56 km with reflector,
what i want to know about where that take place, temperature, humidity ?
I try to connecting two BH 20 where distance is 56 km between them. The result i have headache they are not connected. Master located top of hill and mounted on 100 meters tower, slave mounted on 80 meters tower. average temperature 30 degree celcius, humidity in two location 70% . There are no signal blocking object between them.
Any experience or i have to make repeater between them? so operational distance about 30km.
Thanks.
I’m assuming you’re talking about 5.7BH modules here. Any water between them? What is your b/w rate set to? It’s easier to align them when they are set to 10Mbs, not 20Mbs. What version of software are you using?
Yes, it’s about 5.7BH. there’s a small lake( but i rather call it just a natural pool, so small for saying it’s a lake) between them.
I set BH rate at 20mbps and my software version is 7.0.7
I also have try to set it’s rate at 10mbps but nothing help.
I am curiouos that 5.7BH couldn’t reach each other on 56 km distance.
Any technical things should i do/change on the BH ?
Thanks.
first you need to be sure the units are talking to each other-- on the bench in the same room.'
I asume you have one set as master and the olther slave, on the same channel, color code etc. your distance isn’t that great. we have one link solid at 24 miles in indiana. many at 10-15 miles
md wrote: first you need to be sure the units are talking to each other-- on the bench in the same room.\'
I asume you have one set as master and the olther slave, on the same channel, color code etc. your distance isn't that great. we have one link solid at 24 miles in indiana. many at 10-15 miles
56km is 35 miles.
md wrote: first you need to be sure the units are talking to each other-- on the bench in the same room.\'
I asume you have one set as master and the olther slave, on the same channel, color code etc. your distance isn't that great. we have one link solid at 24 miles in indiana. many at 10-15 miles
the units can be talking each other, i've test it in order to connecting 2 rooms separated about 5 meters, for a week. consider with temperature(30 degree celcius) and humidity(70-80%) where my 5.7BH20 mounted, i am sure that 35 miles(56 km) is not enough to make them talking each other.
or maybe 3 towers national television relay station between the master dan slave, contributing enough for bad interference.
now i make a plan to build a repeater between them so each couple distance for about 20 miles.
Or any suggestion about optimal settings would be very appreciated.
Thanks.
Use the Spectrum Analyzer at each end to identify possible interference (with opposite end turned off) and measure signal strength from your equipment (with opposite end in master-mode).
Also, verify RF LOS using topographic maps. Consider the Fresnel zone radius and earth curvature at the midpoint (45 & 202 feet, respectively, for a 35-mile link) and at any other points where the clearance is marginal. On flat ground you’d need twin 247-foot towers to achieve Radio Frequency Line Of Sight.
I have a new 27-mile, 10mbps, 5.7BH link – on fairly flat terrain – with 130 and 100-foot towers at nearly tha same elevation. Fresnel and earth curvature would normally be a problem, but a shallow river valley adds enough clearance to make it work. The likely problem area is 6 miles from one end where a knoll rises to within 20 feet (if my calculations are correct) of the Fresnel zone. I’m waiting to see if the link is affected when the corn growing on the knoll reaches its full height of 8-10 feet in a couple months.
That’s some tall corn. lol
The corn was likely over 10 feet this year, but there was no noticeable effect on the 27-mile link; my LOS calculations were apparently correct. I do, however, have a 5-mile link with the reflector only 15 feet off the ground that has degraded this summer, presumably because of the corn.
How do you determine earth curvature on links like that?
The theoretical limit is 35miles under perfect conditions with reflectors at both ends and perfect aiming. Put some interference into the system and it’s highly unlikely that you will maintain a link.
Repeating is the right answer.
Calculating earth curvature:
Draw a piece of pie; a triangle with two equal sides and the third side curved. The curve is the surface of the earth; the ends of the curve are your two antenna locations. The point on the piece of pie is the center of the earth; the two equal sides are earth-radii, ~4000 miles.
Draw a straight line that cuts the piece of pie in half (again, 4000 miles). Draw a straight line that connects the ends of the curve (the distance between your two antennas, or at least close enough). These two lines meet at a right angle. You now have two right triangles – back to back; mirror images of each other – superimposed on the piece of pie.
Have you seen the Wizard of Oz? Do you remember what the Scarecrow says when he gets his brain (diploma) from the Wizard? He attempts to recite the Pythagorean theorem, but he gets it wrong. (In the Broadway script, anyway; I’m not sure about the movie.) To calculate earth curvature, you don’t need a diploma. You need a brain.
The Pythagorean theorem is, in a nutshell (equation), “A-squared plus B-squared equals C-squared.” A and B are the shorter sides of the triangle that join at the right angle; C is the hypotenuse, the long side opposite the right angle. For our purposes, we’ll instead say: “the square root of [C-squared minus B-squared] equals A.” C is the radius of the earth; B is half the distance between antennas; A is the radius of the earth LESS the earth curvature.
For a 26-mile link, this computes as: “the square root of [4000-squared minus 13-squared] equals 3999.9788," which is .0212 miles less than 4000 miles (earth radius), or about 112 feet.
Hopefully, the picture you’ve drawn makes everything clear. Except, of course, why the Wizard didn’t grant the Scarecrow his wish.
Thanks, perfectly clear. Just didn’t know if there was something more involved in the calculations or not.
I especially like the part about needing a brain. lol