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wireless 5km p-t-p, why results are horrible?

Posted: Wed Dec 31, 2008 9:14 am
by wireless12
helloo friends.

i hav just made a wireless point to point of link 5 km , but the results are just horrible. but there is no ping timed out between them and the ping varies frm 1ms - 3 ms.

Hardware use:
1. RB411+R52 + 26 dBi GRID ANTENNA ON BOTH SIDES
2. LINE OF SITE IS VERY VERY CLEAR( 80 FEET MAST INSTALLATION BOTH SIDES)
3. LOW LOSS HALF METER PIGTAIL
4. FREQUENCY USED = "5860 "
5. VERY LESS INTERFERENCE.


RESULTS:
1. POOR SIGNAL LEVEL = -91 dBm
2. OVERALL CCQ = 45% - 55%
3. SIGNAL TO NOISE = 16-20 dB
4. VERY LOW THROUGHPUT


SO, anyone hav any idea where is the mistake, why i m not able to see good results at this small distance link.

here are few attachments of my configuration:

Re: OH..MY.....GOD!!!! what is happening?

Posted: Wed Dec 31, 2008 10:01 am
by npero
Try to change antenna a to anntena b.

Re: OH..MY.....GOD!!!! what is happening?

Posted: Wed Dec 31, 2008 3:05 pm
by InoX
5860? Are you sure the antennas are good for 5860?

Re: OH..MY.....GOD!!!! what is happening?

Posted: Wed Dec 31, 2008 4:24 pm
by roc-noc.com
Are you sure you have your grid antennas assembled correctly and the same at both ends? The feed horn in the center should be running to the the short sides. See my crude diagram below. The feed horn is in the center.

|||| | ||||| = correct

|||| - ||||| = wrong

Both antennas the same polarity? Bad antenna cable? Bad or disconnected pigtail? U.fl pigtails can pop off during assembly or rough shipping.

You should be seeing around -50dB based on your description.

Good luck,

Tom

Re: OH..MY.....GOD!!!! what is happening?

Posted: Thu Jan 01, 2009 8:51 am
by wireless12
5860? Are you sure the antennas are good for 5860?
ya i m almost sure antenna are good. for 5860

Re: OH..MY.....GOD!!!! what is happening?

Posted: Thu Jan 01, 2009 8:53 am
by wireless12
Are you sure you have your grid antennas assembled correctly and the same at both ends? The feed horn in the center should be running to the the short sides. See my crude diagram below. The feed horn is in the center.

|||| | ||||| = correct

|||| - ||||| = wrong

Both antennas the same polarity? Bad antenna cable? Bad or disconnected pigtail? U.fl pigtails can pop off during assembly or rough shipping.

You should be seeing around -50dB based on your description.

Good luck,

Tom
i think i hav assemed correctly... and both antenna are same in polarity..

Re: OH..MY.....GOD!!!! what is happening?

Posted: Thu Jan 01, 2009 8:58 am
by wireless12
hii, i would like to add one more thing.. before hooking up these units on mast.. i check them in my lab but wihout any external antenna,when i placed both mikrotik 10 mts away frm each other in my lab, singal were arround - 45 db, signal to noise was also good, and throught was good too..and imediatley after testing them i hooked them on the mast..but it shows por performance on the mast.

Re: OH..MY.....GOD!!!! what is happening?

Posted: Thu Jan 01, 2009 3:12 pm
by InoX
I think the cards are damaged. Try with CM9 for example. Low power cards.

Re: OH..MY.....GOD!!!! what is happening?

Posted: Fri Jan 02, 2009 5:56 am
by jwcn
Yep, this is why you should never use cards without some type of load or antenna connected to them.

Re: OH..MY.....GOD!!!! what is happening?

Posted: Fri Jan 02, 2009 8:51 am
by wireless12
I think the cards are damaged. Try with CM9 for example. Low power cards.
how can these card are damaged i never expereinced such thing. i m using these R52 for a long time. even R52 is less then 100 mw, is it not lower enough as far as power is concerend...?

Re: OH..MY.....GOD!!!! what is happening?

Posted: Fri Jan 02, 2009 8:55 am
by wireless12
Yep, this is why you should never use cards without some type of load or antenna connected to them.
thx @jwcn

i m liite surprise to accpet that these card are now damged as u said. but i always test all my mikrotik before hooking the on the mast, numerous time i hav doen it, i never got my card damaged if i checked them without any external antenna...

Re: OH..MY.....GOD!!!! what is happening?

Posted: Fri Jan 02, 2009 1:41 pm
by janisk
R52 cannot be damaged in that way (powering up and transferring without antenna)

Re: OH..MY.....GOD!!!! what is happening?

Posted: Sat Jan 03, 2009 4:01 am
by jwcn
How do you figure?

Re: OH..MY.....GOD!!!! what is happening?

Posted: Sat Jan 03, 2009 6:55 pm
by roc-noc.com
R52 are pretty darn sturdy. They only output about 79mw output and don't have any warnings like the higher powered devices. I use them for most of my links.

Unless there was lightning, I have never seen a blown output on one where I have seen many blown R52H and Ubiquiti miniPCI cards.

I suspect he has bad coax, connector, or something wrong in the antenna system.

In any case, he won't find out until he takes them down.

Tom

Re: OH..MY.....GOD!!!! what is happening?

Posted: Mon Jan 05, 2009 4:45 pm
by noam_chom
I have about 20 PTMP 6-10km backbone - links.
I've experienced a problem like yours few times , and almost always the solution was changing the pigtail.
Nowadays it's hard to find a good pigtail.

Re: OH..MY.....GOD!!!! what is happening?

Posted: Tue Jan 06, 2009 1:24 pm
by wireless12
I have about 20 PTMP 6-10km backbone - links.
I've experienced a problem like yours few times , and almost always the solution was changing the pigtail.
Nowadays it's hard to find a good pigtail.
i think u are right..cost reduction also brings reduction in quality.

but i hav changed the pigtails too...the prob remain unchanged.

Re: OH..MY.....GOD!!!! what is happening?

Posted: Fri Jan 09, 2009 6:47 pm
by noam_chom
You could try pointing antena upwards (look at the picture).
Image

I've had a problem like yours when we were doing 26km link over lake, but i solved it pointing antenna upwards.

I would also recommend you to calculating,the fresnel zone clearance for your distance.

Re: OH..MY.....GOD!!!! what is happening?

Posted: Sat Jan 10, 2009 12:37 pm
by wireless12
You could try pointing antena upwards (look at the picture).
Image

I've had a problem like yours when we were doing 26km link over lake, but i solved it pointing antenna upwards.

I would also recommend you to calculating,the fresnel zone clearance for your distance.
really tht is great..but shd i lift both antenna or just at one side only.

Re: OH..MY.....GOD!!!! what is happening?

Posted: Sun Jan 18, 2009 3:00 am
by noam_chom
Yes you should lift both antennas.
But I could'nt find a better picture :), and I am not so keen in drawing.

regards.

Re: wireless 5km p-t-p, why results are horrible?

Posted: Mon Jan 19, 2009 5:46 pm
by nickb
It could be one of two things, in my opinion:

1) Antenna Aim is off
2) Your Fresnel is "too good". If your Fresnel is more than 1.0, you will have a reduction in signal strength (depending on the Fresnel). I have seen many cases where antennas were too high for a particular location, resulting in too good of a Fresnel. You may need to lower your antennas, especially with such a short link and such tall towers. I suggest using Radio Mobile to determine optimum antenna placement. It can also help you with azimuth readings for aiming antennas.

Here is an example - note the "RX Level" number, this is the predicted receive signal at the "Receiver" side.

Optimum Fresnel
Fresnel-1.png
"Too Much" Fresnel
Fresnel-2.png