We are operating a 44km link overseas in Turkey, using a pair of C5C with 36dB dishes. We have good outputs considering the distance and conditions, but we experience severe thermal ducting in hot weather and high air pressure conditions (anticyclonic). Output is going from 234/234 to 18/18 or even worst, bouncing for several hours and then getting back to normal, lowering bandwidth does not give good results eather.
We are trying to mitigate this and look at several options (dual link, frequency/spatial diversity, backup link etc…) but none seem good for our purpose.
Would licensed frequencies be a good alternative or is thermal ducting affecting all frequencies at once?
Most frequencies are effected in some way by thermal ducting. Though my understanding is that lower frequencies might be less effected. (I am stretching way back into my HAM radio days for that info so take it with a grain of salt)
That said, I know 5 and 11 GHz are effected by the issue. But you are somewhat in luck, Mimosa has a whole presentation on how they dealt with the issue. https://mimosa.co/blog/deploying-a-diversity-link
If you would like I can summon the great @DustinS who can answer any of your other questions on their solution. Which is WAY cheaper then if you were to buy a diversity link from most other companies.
I watched the video dozen times, i understand the concept, spatial diversity looks great from that angle, the case is super similar to ours anyway, frequency diversity seems to be another way, we thought about a dual Link with c5c on different frequencies also but I fear that all frequencies may fade at once… We are looking for metro ethernet solution with a game operator nearby, it may be a better solution
The case study doesn’t explain the calculation of the spacing between the dishes…
Which is why I tried summoning @DustinS, he would have access to the math stuff…
If he doesn’t show up in the next day or so I will use a more powerful summoning spell.
Our old CEO did all of the math and we ultimately didn’t end up using the spacial diversity setup. Turkey Licensed also doesn’t exist anymore due to BTK in Turkey.
I would think running two links with different frequencies and have routers on both sides of the links doing OSPF or some kind of link aggregation, this might be your best option.
Can I ask what method you did use? I am looking at a 13 mi shot. I am going go try and use an A5C in the fashion that you did your diversity setup. I have lots of height on one side so am going to ‘try’ to make the link not coordinated (high side --> low side) to see if that will help.
Hi, our Link is 27mi, we couldn’t find any location in between to shorten it. Considering the costs of a new tower to host that much dishes etc we decided to go with metro ethernet directly on the island, provided by a nearby gsm operator. The operational cost is higher, we will run door by door to get a hundred new subscribers to cover it. Growth was ineluctable anyway. The link works great with a pair of c5c on that distance for 95% of the time, (234/234mbps) we will keep it as a backup, but thermal ducting is a filthy mess… Had we had a proper tower i would have gone with a double link (frequency diversity) but the risk was higher and we had the metro opportunity, we chose economic risk over technical risk…
Hi Antoine, May I ask – which 36dbi dishes were you using? Thanks