No, the fresnel zone does not depend on the beamwidth of the antenna.
It depends only on frequency and distance.
Very interesting tread changeip.
Some pictures and last info would give it a nice end.
The tread is dead now for 20 days, any last info?
And yes, vote to make it sticky. This is a very educational topic for lots of us… well done!
R.
True. But the beamwidth does have an effect on the amount of energy transported in the LOS tunnel.
Thus with the same Fresnel and same radio output you get better signal (=more energy) on the other end. Thus higher readings. The negative impact of the ´blocked´part of the Fresnel is the same in % but since the amount of signal received by the other end is higher, you have better signal levels.
Now before we think this can then also be achieved by just more power on the transmitter. It is not the same.
Bigger dishes or bigger mesh antenna’s are not only better in converging (´tunnelling´) the signal, thus delivering more energy at the other end, but are also better in ´hearing´ in its focus direction when receiving the signal. So you win twice here instead of only once with higher power outputs. Aiming becomes more important now.
But this is an important element some of us forget. Just increasing power is usually not the way to go.
(Apart from the fact that most radios perform better under mediate power settings then max. settings. If possible leave them at default or drop a bit.)
Look at this radio link issue as an adjustable focus torch that you use to signal a guy with binoculars some miles away.
If your torch’s light beam is wide you’ll have a nice light close to you but your guy at the other end won’t probably see you with its bare eyes, special if there are lots of other light around you and him.
Now converge the beam of the torch to the max and he might pick up the light if you point at the right direction. Your light will stand out compared to other surrounding light seen by the ´looker´.
It will make it all much better for the distant guy if he then starts to use binoculars.
You could also put a much higher voltage to the lamp of the torch when not converged yet. Your other guy will then also pick up the light from you, just before you bulb burns…
In the ´receiving end´ (the ´looker´) imagine the following:
When he uses bare eyes or a cheap binocular, he will only see the torch if it is focussed heavy and pointed in his direction or when it is unbelievably bright. But at the same time he will also see other lights in its surroundings, like a car using its head lights while hunting rabbits… (Doppler radar hunting for rain…).
Now, if your ´looker´uses a telescope he will pick up your torch easy if he is pin pointed to the torch while probably doesn’t even see the hunters car any more. You can even put some lesser volts to the bulb to extends it life time (not too low, the bulb then also start becoming to work less and shortens its life time. Just like a radio.)
In using the high dB dish antenna’s you do both. Converge the beam and maximise the hearing while at the same time keep as much of unwanted signal out of your receivers (so lower noise level)
The only risk here is that when a strong signal happens to fall into the antenna and the signal is picked up by the receiver it might blow its receiver circuits.
(Imaging the ´looker´ uses the telescope to look comfortably at the torch and then lightning strikes direct in your path of vision. Worst case is he looses sight for ever… In radio terminology, it will damage your receiver.)
So now you also have a tip to ´blow´ your competition out of the sky.
I know, not the purpose of this topic, but imagine you are the competition… be aware!
Very informative post, I will be interested to see how it turns out.
have you solved your issue?
- try to add 50m antenna pole on the side which is lower (to avoid power line radiation. the height is depended to their transmit voltage)
- try to reduce the 20mzh channel to 5mzh, if that helped then use a more powerful card or use a amplifier.
- try to replace your antenna where you have a sharp (more towards 90 degree angle on those powerline)
We had very much the same problem as you did a few years ago.
when there was a high power line in the path similar to what you have in one of the photos.
if the power line has angle it will do unknown and strange behavior which no-one may never know.
although in these scenario we did a test with dual antenna and 11n card and it did greatly improved the speed and the signal.
Beside installing a tall poll at low end I can’t recommend anything.
to test , you can use a GI pipe and use a temporary cable to hold it for signal testing and see if going above the power line will help or not…
in our case 50m above the power helped a lot.
Good luck
Kan you please send me the google earth place marks and the hight of each antenna from ground I would like to run it in a tool we have
you can mail it to erastus at theweb.co.za
It would be very nice to run it in our simulator. Mark each spot with place mark and then mail the place mark
Hello, people.
Reading the entire posted. I realize maybe a design error in the pacwireless new grids. I recently installed a new wireless network with about 6 25km distance links. Each site has the same config as the others, same antenna, same board, same minipci. I found out my links barely can get -78dBm Rx signal. I have test another minipcis and have the same signal strenght. The only option left is to try another antenna to test.
I would like to ask you people to share your experience with these grid antennas.
Best regards..
Hi changeip, which software is it? that graphs the signal from RB’s…
MRTG
Great thread.
I have an almost identical 5Ghz backhaul link. Much much better looking fresnel zone however.
There is a hill at approx the halfway point, not quite in the zone.
The link runs almost constantly at -66 both ends, EXCEPT on hot and calm dog days when the trees on the hill are giving off quantities of water vapor.
Then it drops to -74 to -76 and stays there until the wind comes up or the water vapor dissipates.
I totally agree with mramos and jcremin.
Hello Forum Guru
Let tell you some facts based on your Radio Mobile information, per experience I have many Links working even with more distance using Mikrotik’s without problems, but the whole idea of Radio mobile is to help to avoid you waste time deploying a link that won’t work, the signal predictions are good in Radio mobile if all data in is correct and results are correctly interpreted.
I’m seeing many issue on your information posted:
1- You configured a maximum TX power of 27dBm, I’m not sure but I do not think this TX power is possible, maximum 25dBm depends of the Wireless card used.
2- Your received sensitivity is too good, for a link budget you have to be conservative so -93 dB is too good, you should configure on Radio mobile a little more conservative value like -86dB
3- Antenna Gain is important, also antenna pattern, so if you use the right antenna gain and the right antenna pattern then should be not poroblem, I can not tell if this correct based on your information without seein the whole prpject file.
4- The signal is blocked more than 50% on certain point of the path by a hill, you have to calculated the fressnel zone to verify this will be an issue or not.
5- Never deploy a link is you do not have a margin at least of 20dB’s, on your Link budget the Profile shows on few dB’s margin, so weather, atmospheric events make the signal fade a lot, so with the few margin calculated by Radio Mobile you won’t have a stable link.
In summary Radio Mobile works only is all data is entered correctly and some extra conservative values are considered.
remember the law “Trash IN = Trash OUT”
If Link budget data is not entered correctly the link budget is useless, also if all is right link budget is also telling you never deploy a link if you do not have at least 20dB’s S/N level to account for FADE
Go higher!!! metal buildings are mirrors for wireless. I dont know if you have any water ( as in lakes ) but they can have the same effect. The best thing is higher or move away from the metal building.
I would like to know the end result too, seems like the problem was still there?
When I was reading this, I seen the picture of the air conditioning unit.
Also seeing the graphs, where I believe it was between 4 am and 6 am where it got better…
My theory is that, since this building is a data center, that AC unit would probably be going most of the time, but possibly the days, as intermittent as they were, when the temprature falls low enough that AC is not needed in the building, but just use outside air, then it would shut down. Im sure the unit on the roof is actually an Air Make up Unit, not just an AC unit.
It would be interesting to see if the outside temp for that area fell low enough during those nights so that the AC compressor unit was not working, or even if that AC/ Air make up unit was shut down for that duration. The hot air exhausted from the unit may have been effecting the link, when it was off, it got better.
Hopefully we find out for sure if the link got better???
My OTHER Idea was that that may not be doppler radar ( Weather) It may be Radar for an airport? I had a couple links that were to the North of my AP, and in the direction of the airport, that ALWAYS had a very low signal, -78 - -84. at some point that same hardware was moved to locations south of the AP and even further away and the signals got up to -70. There was no LOS, there was trees that were taller then the height of the AP, and even a house litterally in the way of the shot. To be honsest Im suprised it works… as for the advice of if there is less then 20 DB fade margin, dont bother setting up the link, well, I think its faster and easier to run the data in radio mobile, and see if it is remotley possible, then just set it up, after all you obviosley need the link, why else are you trying to get it to work?
I did get this to work a long time ago - we ended up using the 3ft pacwireless dish on both ends versus the grid dish I started with. Its a very stable link now, almost 200 days uptime I think. The main issue was temperature inversions on the path. The link barely changes signal now with the 3ft dish, very solid.
sorry about hijacking this thread but what about that program that visually showed the fresnel zon and his link across the vertical slice of the land. what program is that and how do i get it 
Radio Mobile, here http://www.cplus.org/rmw/english1.html
Hi,
Im make link for 36KM distance links :
2RB433AH
2XR5 with cables.
Dish 32db dual 90cm
antenna dual 32db
the link working very good the signal is :
If this would not be enough, you can also try plugging in signal repeaters on specific spots which has low signal levels. This is pretty much applicable on schools which have class rooms with mobile phone signal jammers but if you still want a wireless internet signal, then might as well right. ^ your network looks really impressive if that covers the 36km distance.
Greetings!
Does anyone have antenna templates for 2,4 and 5 GHz, that i can import in RadioMobile?
If you join the Radio Mobile Yahoo group (mailing list), you can get access to the Files section of the group site at http://groups.yahoo.com/group/Radio_Mobile_Deluxe/ which has many useful antenna pattern files, including many patterns for Pacific Wireless (Laird) antennas.