Not much experience with this , but I’m getting some wacky behavior in some links and would like feedback from anyone with any knowledge of this.
I have three backhaul nodes all sending and receiving to the same geographical point. Over the past few weeks the data rates on these links have varied wildly. I’ve used every frequency from 5180 to 5825 Ghz and see no change in behavior. These links have been in place for several years and this has been a real pita lately. They all face a northerly direction and are placed on the horizon about 60 degrees apart from the collection tower. They vary in distance with two being about 6 miles out and the third about 11.5 miles out.
Due north of these paths , from 1 to 5 miles , there is a large wind farm that has been built within the past year . We’ve also had a very wet spring and I’m trying to determine if the windfarm is causing my grief (possible phase cancellation effects) or if it may be fresnel induced losses caused by vegetation growth . Elevation delta from south to north is about 40 ft. the antenna’s are 85 to 100 feet up. I’ve run a spectrum scan ( ubiquiti airview) and see nothing looking north to warrant what I’m experiencing. I’ve also changed cables , bulkhead fittings , radio cards ,and even the antenna feedhorns to no avail. Why won’t my rates stabilize?
I have dealt with a few windfarms that are present inside my coverage area.
One of the windfarms in medium in size 24 x 1.6MW units. We had two separate problems with these turbines. The 1st problem affected our backhaul. We were using a 2ft 5.xx GHz Dish as a backhaul for our tower. The total link distance was ~16km, and we worked with the turbine company in their initial layout phases to make sure the Fresnel zones were clear for our backhaul. After the turbines started to be installed, we noticed significant issues with the link. It would periodically drop, we would get sporadic ping spikes, and the data rates would not hold steady.
We had some dealings with multipath in the past, and this was appearing very similar. We plotted the ~5 degree beam across the link distance from both locations and found that while the fresnel zone was clear, the main lobe of the signal from both locations was in fact hitting turbines. Luckily for us we had another site ~11km away from our tower. We replotted using a ~3 degree beamwidth antenna (3ft dish) from this new location and we found that the main lobe was now missing all the turbines in both directions. We installed the equipment and this solved our problem.
The 2nd windfarm we had to deal with was small 5 x 2MW units. However they were completely uncooperative. One of their turbines was in a direct path with a 5 GHz backhaul. We complained during their planning and layout phase that it would cause problems but they refused to move it. After the turbine was up, we did experience problems. I reported it to them, and they hired an ‘independent’ company to investigate. They did a 3d plot of the 1st fresnel zone, which technically cleared the turbine structure by ~10 ft. I attempted to explain why I felt it was inadequate clearance, and the final result was a complaint filed with the regulatory body in my country. However since they did not have strict rules that must to followed, only recommended guidelines for wind turbine placement around communication towers I had no recourse other then if I wanted to hire a lawyer and fight it in court. Our final solution was to install a repeater tower to effectively go around the windfarm, which was much cheaper then going to court.
That was my experience with backhauls and windfarms.
