MW Radio Links in Coastal and Wet regions

[mohamad]

Dear all friends,
What important things should I consider in MW radio link designing in Coastal and wet regions?
I designed a MW link with fade margin of 30dB and SESR below 54*10^(-5)*L/2500 with regards to ITU recommendation. This link will carry very mission critical data so this link never be failed.
Please help me about design of this link.

Thanks a lot,

Mohamad

[Cost_Reducer]

Hi,

i think, you should think about a protection path in the mw link, e.g 1+1 HSB configuration or another configuration of mw link.
How long is the path, what frequencies you will use and is this a sdh or pdh link?

Regards

[da_manole]

what frequency ,and what is the length of the hop.

[kaka.enine]

if this region have a potential causing reflection,

perhaps yu have to prepare yur link with diversity protection,
so it will be 1+1 SD

[Stantheman]

Hi Mohamad, if this is indeed a mission critical link then you seriously need to consider path protection plus select the right equipment/frequencies for the conditions.

I am not an expert on this, so please seek out someone who is, either in this forum or another, and get their help.

A good forum for MW is the Pathloss forum hxxp://www.pathloss.com/forums/index.php , this post is typical of the good things to be found there hxxp://www.pathloss.com/forums/showthread.php?t=121 , attached is the document on protection and diversity that is referred to.

There have been some very good resources posted in this forum, under the Library and Transmission sections. Here is a good book on the subject:-

http://www.finetopix.com/showthread.php?t=4291&highlight=microwave


If you are unsure of how to handle the design of the link and do not have time to learn the key theoretical and practical issues about MW (and that could take years) , then you would be best to engage someone who is an expert on MW , or get your chosen equipment vendor to do this work for you. I have seen a lot of "disaster" MW links out there ... designed by people who thought they knew what they were doing.

All the best with your project!

BR's, Stan.

[Stantheman]

a good overview document

[byja]

If the link goes over a large body of water, it's always a good idea to use space diversity. No base band switching space diversity, a proper one, with IF combiner. That way you can even add frequency diversity as well, maybe even add an angle diversity on diversity antenna (tilt diversity antena upwards a degree or so).
If you can, try to design a path so that the reflection point lies not on a water, but on an island or peninsula.
One more thing to consider, constantly overlooked. If your link is to be working near the coastline, with higher temperatures and high humidity, always make sure you have the equipment which is designed with extra protection against humidity and salinity. For example NEC has a special casing for ODUs working in such conditions. I've seen photos of standard NEC ODUs eaten away by the corrosion. 3rd party products, such as RF couplers and antenna poles are usually less protected than ODUs from respectable manufacturers, so pay extra attention to that as well.

BTW flatlands, farming lands and wetlands are just as bad as water surfaces. Here's an example with one of links I've been working on. 70km, over a long stretch of farmlands, wetlands and a river as well:
http://tesla.rcub.bg.ac.yu/%7Evmarko37/coverage/fading.gif

[mohamad]

Hi,

i think, you should think about a protection path in the mw link, e.g 1+1 HSB configuration or another configuration of mw link.
How long is the path, what frequencies you will use and is this a sdh or pdh link?

Regards

Hi,
The link is already 1+1 HSB. Path lenght is 30 Km, in 7 GHz band and link is PDH.
If I use space diversity antenna for this link, can I be sure that reliability of this link will be acceptable?

Thanks

[Cost_Reducer]

Mohamad,

does your equipment support baseband switching or IF combining?
For real space diversity you need equipment with IF combining. This is better than baseband switching.
If you use IF combining SD you can be sure that the reliability is much better than a link without SD.