Visit RFCafe.com Thanks for visiting RFCafe.net Thanks for visiting the RF Cafe Archives Thank you for visiting RF Cafe Thank you for visiting the RF Cafe Archives!

Absorption losses of different terrain types - RF Cafe Forums

The original RF Cafe Forums were shut down in late 2012 due to maintenance issues - primarily having to spend time purging garbage posts from the board. At some point I might start the RF Cafe Forums again if the phpBB software gets better at filtering spam.

Below are the old forum threads, including responses to the original posts.

-- Amateur Radio
-- Anecdotes, Gripes & Humor
-- Antennas
-- CAE, CAD, & Software
-- Circuits & Components
-- Employment & Interviews
-- Miscellany
-- Swap Shop
-- Systems
-- Test & Measurement
-- Webmaster

Gavin
 Post subject: Absorption losses of different terrain types
Posted: Thu Feb 07, 2008 8:48 pm 
 
Lieutenant

Joined: Thu Feb 07, 2008 8:46 pm
Posts: 3
Hello,

I am modelling an EDACS system operating at 900MHz in Mentum Planet and would like to use the clutter (map of various terrain types) file for the area to improve the accuaracy of my coverage plots. To do this I need to know the absorption losses at 900MHz for various terrain type such as:

Fresh water
Sea Water
Forest
Dry ground
Residential
Dense Urban
Core urban (whatever that is)
Industrial

Can anyone lead me towards some information on this?

Regards,

Gavin Hill


 
   
 
nubbage
 Post subject:
Posted: Mon Feb 11, 2008 6:08 am 
 
General
User avatar

Joined: Fri Feb 17, 2006 12:07 pm
Posts: 218
Location: London UK
Hi Gavin
I have contacted a few Planet users to get some help on this one. Do you really mean absorption by these media or do you mean the permittivity and loss factor on reflection from their surfaces?


 
   
 
Gavin
 Post subject:
Posted: Mon Feb 11, 2008 8:13 pm 
 
Lieutenant

Joined: Thu Feb 07, 2008 8:46 pm
Posts: 3
Hi Nubbage,

Thanks for looking into this, as I understand it the 'clutter absorption loss' is the loss resulting from absorption by foilage, buildings, etc which is added to the path loss, or vice versa subtracted from the signal strength. So I think your description is probably more apt, although the permittivity at 900MHz will have little effect.

In Planet (Ver 4.3) the setting I am changing is in
'Propagation Model Properties' under the
'Clutter Properties' tab where I select
'Edit CPA'.
This brings up a table with the various terrain types that I noted in my first post. The variables that I am changing are under the
'Clutter Absorption Loss (dB)' heading.

Regards,

Gavin


 
   
 
nubbage
 Post subject:
Posted: Tue Feb 12, 2008 10:48 am 
 
General
User avatar

Joined: Fri Feb 17, 2006 12:07 pm
Posts: 218
Location: London UK
Hi Gavin
I have received unhelpful feedback on my enquiries into the settings for Planet. The most helpful was "to consult the manual", the least helpful was "to enquire at the British Museum" (the group use the very latest software at a world-famous Swedish system manufacturer).
More helpfully, I offer you a French graph of forest attenuation which agrees well with another source I have. This predicts 11dB/100m in winter (assuming deciduous trees with no leaves) and 22dB/100m in summer with wet leaves at 900MHz. There is also a polarization dependence, but the above figures are for vertical pol, normally used for mobile coms.
I will up-load my graph via image-shack as the clip board is ineffective on this site.
Although not strictly valid below 1000MHz, there are good design parameters for rolling terrain and sea paths in the ITU Radio division report ITU-R PN.530. Parameters for urban clutter have been hotly debated for years and I am now not so sure where the debate has led by today. More next posting.


 
   
 
nubbage
 Post subject:
Posted: Tue Feb 12, 2008 11:04 am 
 
General
User avatar

Joined: Fri Feb 17, 2006 12:07 pm
Posts: 218
Location: London UK


 
   
 
Gavin
 Post subject:
Posted: Thu Feb 14, 2008 8:04 pm 
 
Lieutenant

Joined: Thu Feb 07, 2008 8:46 pm
Posts: 3
Hi Nubbage,

Thanks for the feedback, I think the graph will prove to be very helpful. As for the Planet user who suggested "Use the manual", I have, and there are no indications for absorption losses at different frequencies.

Regards,

Gavin




Posted  11/12/2012
RF Stencils for Visio v3.1 by RF Cafe
RF Cascade Workbook 2018 (GS) - RF Cafe
About RF Cafe Archives
Kirt Blattenberger - RF Cafe Webmaster
Copyright: 1996 - 2024
Webmaster:
    Kirt Blattenberger,
    BSEE - KB3UON

RF Cafe began life in 1996 as "RF Tools" in an AOL screen name web space totaling 2 MB. Its primary purpose was to provide me with ready access to commonly needed formulas and reference material while performing my work as an RF system and circuit design engineer. The Internet was still largely an unknown entity at the time and not much was available in the form of WYSIWYG ...

All trademarks, copyrights, patents, and other rights of ownership to images and text used on the RF Cafe website are hereby acknowledged.

My Hobby Website:  AirplanesAndRockets.com

spacer