Unstable MW radio links

[Al Salihi]

How can you check the Local weathr is it from http://www.dxinfocentre.com/tropo_mid.html#hour12?

About antenna height in pathloss I put the min height but actually all antenna are setting above 25 m for physical LOS survey

Time of outage is during late night and takes 3 hours and then RSL variation under fade margin (unstable) until morning links up

As per civil work all tower, antenna are fixed well

I am checking about software upgrade to the radios and found nothing has been happen !

[Al Salihi]

Thanks for advise ...

How can you check the Local weathr is it from http://www.dxinfocentre.com/tropo_mid.html#hour12?

About antenna height in pathloss I put the min height but actually all antenna are setting above 25 m for physical LOS survey

Time of outage is during late night and takes 3 hours and then RSL variation under fade margin (unstable) until morning links up

As per civil work all tower, antenna are fixed well

I am checking about software upgrade to the radios and found nothing has been happen !

[Louis Hayworth]

Take a look at the document I included but based and what you are telling me about the outage time and durration it seams that you are experiencing obstruction fading. The example is the second one on page one.

Do this, input the real centerline in in link files. Then go to the terrain data and input a tree and/or building at the controlling points. Use the typical height of the buildings and or trees you would find in the area you are crossing. For example if the path crosses over a banana plantation the add 7 meter trees at the controlling points. If the path crosses over an olive grove add 5 meter trees. If the path crosses over eucalyptus trees then add 30 meters, basically use typical height for typical trees in the areas. Then calculate the clearance and the obstruction fading. If the path crosses over a rice paddy then assume that you will have a layer of water on the ground and look for out of phase reflection points that are visible to both antennas.

Always do a path design with man-made structures, vegetation and cultivation along the links and look for potential problems. Then calculate the impact of the potential problem. If you can calculate a problem then you go out in the field and verify if your asumptions are really there. Let me tell you that along the valley you will find, trees, water from irigation and buildings.

As far as the weather goes the link you provided if for HF and VHF propagation, I don't know if this is applicable in your situation because the ducts they are talking about are high in the atmosphere, keep in mind that your links travel along the ground from 0 to 100 meters and what I said earlier is still true, the links are relatively short and not likely to suffer from ducting.

Let me know what you find and send me the link files with the real centerlines and where you think the trees/buildings are along the links and we can look at them again. Remember that you can see what is along the path by inserting the links in google like I did and then go along the paths and mark down where you cross large trees or buildings.

Let me know.

PS. I had to compress the file a lot to upload it. If you give me your e-mail I will send it directly.

Louie....

[Al Salihi]

Seems you are v.experience engineer, appreciated your help and support

Man-made structures / vegetation/ tree Obstructing has been already taken in design as antenna height that on field is between 25 m and 40 m



One thing I can tell there is really irrigation on this agriculture lands that have rice paddy..etc need water as I heard yesterday from site engineers BUT that is usually NOT irrigation for specific period

You are true ducting phenomena is not in there since links are using hi Freq and short distance, check http://www.dxinfocentre.com/tropo_mid.html#hour12 for ducting forecast


This is my e-mail ahmed.rashied@yahoo.com



Keep in touch on on next step!

[Louis Hayworth]

One thing I would like to know. How long are the links in service. Have you had the same type of weather before that you are having now. Has it affected the links before. has anything changed since the links went into service.

louie.....

[Al Salihi]

How long are the links in service ? some are newly and some are due to 2004


Have you had the same type of weather before ? Yes but was in may NOT Feb

Has it affected the links before ? yes but not that as much as today


has anything changed since the links went into service ? no

As u said ,the problems affect all the paths at one time,I expect non-normal fading situation and want to know how can secure those links , should use SD or uptitle the antenna ?

[Al Salihi]

Once again,
I did re plan link with kmin and Kmax and
I did generate path profile based on actual surveyors reports

But in same area -Upper Egypt I have same problems affect all the paths at one time,

I expect non-normal fading situation like what u said and then want to know how can secure those links, should use SD or uptitle the antenna?

Please it's serious problem want your advise

Those links are still unstable and RSL is dowm/up?

[Al Salihi]

Salaam Brother Imran ,

I am looking for your contact phone number ,location?

Me and Mr Abdul Durrani want to discuss opportunity with over phone ,he knows you well and am interesting to get know each other


Thanks

[Ricky_ATT]

Hi Ali I took a look at one of your paths Abo Qurqas-Giza Luxor and have concern regarding using a such highe frequency with small antennas in a long path, also I plotted the path on Goggle Earth (which you may also use as a tool to help identify obstructions with an exact distance from point A or B) and notice a large flat and wet area which may act as mirrors creating reflection.

The higher the frequency the smaller the lambda which it will it make more vulnerable to rain or mist during the night. So one option is to use lower frequencies or as mentioned before SD configuration.

The modules of Reflection & Diffraction in Pathloss may be of great help by varying the frequency.

[Timothynat]

Yea I mentioned that in my post...

I dont know if that was to help me? Thanks,

But I guess I should clarify my post...

I was just suggesting for people to check their sigs, cause a lot of the links arent updated.

Just trying to help

-C