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New Member
Posts: 23
Registered: ‎09-18-2013
Kudos: 3

Is the corrugated metal roof affecting signal strength? (Reflections?)

[ Edited ]

I have questions about a 6.7 KM PTP link, with Rocket M5, FW 6.0.7 and RD5G-30 on both ends.  I belive the fresnel zone is clear, the only possible incursion could be some trees .3 KM from the AP.  According to Google Earth, the elevation at the base of the trees is three feet lower than the AP.  The AP is 45 above ground level, the station is 18 feet above ground level.  AP is located at 46.560611,-120.692884 and station is 46.607501,-120.637884.

 

The AP is on the east edge of the second building in from the street, 15 feet above the roof parapet.  The station is to the north of the home, in between the home and the fence.  In Google earth, you might be able to see two masts, the station is mounted on the west mast.  

 

Airlink shows the link should be 35 dBm, however after much time I am able to achive only 52-56 dBm on TX signal, and 54-55 dBm on the station.  Chains on each end a maximum of three dBm difference, frequently no difference at least on one end.  Noise is 92-93 dBm.  Interestingly, combined signal strength shows as 51-52.

 

There is a corrugated metal roof on the home at the station.  The edge of the roof is 15-20 feet from the antenna, and ten or so feet below the antenna.  There are corrugated metal roofs to the eaast of the AP, however the roof of that building is 20-30 feet lower than the AP antenna.

 

There are three PTP links from the station to other sites.  I am unable to achive what AirLink predicts on any of these links.  I haven't spent as much time trying to fine tune these links as I have with the backhaul I mentioned above. 

 

What are your thoughts, is the corrugated metal roof(s) the cause of my inability to achieve the signal strength predicted by AirLink, or is it my lack of fine tuning the antenna aim?  

 

Thanks for any thoughts, advice and help!

 

Jeff

Established Member
Posts: 2,045
Registered: ‎07-17-2010
Kudos: 371
Solutions: 86

Re: Is the corrugated metal roof affecting signal strength? (Reflections?)

What frequency and tx power are you using on each end?

 

Are you certain the path and fresnal are clear?

New Member
Posts: 23
Registered: ‎09-18-2013
Kudos: 3

Re: Is the corrugated metal roof affecting signal strength? (Reflections?)

Output power is 24 dBm at 5240 MHz.  I am not sure the Fresnel is clear.  

 

I will calculate the height of the trees tomorrow and reply with what I find.  I am surprised, the 60% Fresnel at .5 km is 13.072 feet.  13 Feet is more than what I would have guessed, perhaps the Fresnel is impacted.  I will also have to figure out how high the center of the beam is at .5 km.  Unfortunatly, I am not a math guru.  

 

Thanks,

 

Jeff

 

 

Established Member
Posts: 2,045
Registered: ‎07-17-2010
Kudos: 371
Solutions: 86

Re: Is the corrugated metal roof affecting signal strength? (Reflections?)

Airlink should show you this information.

 

Have a look.

New Member
Posts: 23
Registered: ‎09-18-2013
Kudos: 3

Re: Is the corrugated metal roof affecting signal strength? (Reflections?)

I entered the path into Radio Mobile web version.  If I understand it, it shows the trees at .5 km, and the fresnel is clear.

 

Interesting, Radio Mobile shows the received signal strength as -49 dBm, which is much closer to the numbers I am able to obtain.  I think I entered the data correctly, however I can't specify the antenna, only the antenna gain.  Is the lack of antenna data causing the difference in numbers between AirLink and Radio Mobile?

 

Is the corrugated metal roofing causing a problem, or do I suck at fine tuning the antenna aiming and need to improve my skills? 

 

Thanks,

 

Jeff

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