We are expanding our network and need to commission a reliable 83km PTP backhaul link in the 5.8Ghz band. We require a minimum stable throughput of 10Mbps minimum.
The profile of the route is shown below:
At the 1614m site, the Mast is 13m high. At the 2324 site, the mast will be 15m high. Fresnel should be good, if anyone can assist by confirming this?
The equipment we intend placing in service at each site is as follows: Mikrotik RB800, with 3x2.4Ghz cards and 1x5.8Ghz DBii F50 Pro. The 5.8 antenna is planned to be be a Ubiquiti 5Ghz Airmax 34dBi Dish on each side.
I am looking for opinions as to if this will work, or should I be looking at placing intermediate sites (at huge difficulty due to horrible terrain in between the two proposed sites).
Have you used http://www.ligowave.com/linkcalc/ it’s free just register, insert co-ordinates and check the results,
Of course if you have a option to use a intermediate site it will make your task much easier?
Have you thought about using a DBii F52n-PRO and Jirous JRC29-Duplex ? This would allow you to use 802.11n/Dual-Chain and provide a bit more speed.
Using MCS3 at this distance with this combo, you would have a 33M fresnel zone and could expect around -65dBm signal. This would provide you with a worst case of 10mbit full-duplex, but probably more.
Hi nz_monkey, n21roadie, digicomtech. I used the link n21roadie provided - thanks. Not sure if my parameters were spot on (Rx threshold?), but I am also coming out at around -52 to-65 dBm on RX side, depending on if I use a 30 or 34dBi dish on the 27dBm card. Fresnel is fine and assuming 25mm/hr rain, link uptime of greater than 99.99%. 32dBm thermal fade margin. All actually looks very solid.
No experience in duplex operation, but may well be brave enough to give it a try.
On both 2 these links the side A is at ~50m height and side B at 200height, the 90% of distance is sea but with no other obstacles.
The 104km link works with 80cm offset dishes + 5GHz handmade feeders on both sides and the 80km link works with 80cm offset dish + 5GHz feeder in one side and 30dbi ubiquity solid dish on the other side.
Both of them are very stable and work for a few motnhs.
Dual-Pol is generally very good, and in most cases if single pol will work, so will dual-pol.
Just make sure you use high quality antennas with as much cross-pol isolation as possible. I used to use the Ubnt/Laird/Chinese style dual-pol dishes and they were OK but got best performance from the JRC-24/29 Duplex antennas, I suspect primarily due to the extra isolation.
While I haven’t been to Zimbabwe I’ve got some experience with long PTP links we set up in Uganda. I learned one thing very quickly, never underestimate the rainy season. There’s nothing like getting reduced to using HF data radios for IRC and email when it’s raining so hard that nothing else works.
