1. VHF Troposcatter Propagation - VHF102
KK6MC
James Duffey
NM VHF Society
VHF
VHF Troposcatter Propagation - VHF102 1

2. What is Troposcatter?
Scattering (not reflection) from inhomogenities (blobs of uneven density) in the troposphere
Allows propagation beyond normal line-of-sight and diffraction distances
Aways present, although strength varies considerably
13 to 15 dB
Varies with time of day, season of year, weather
Very dependent on effective radiated power, angle of radiation
Viable propagation mode from 50MHz (6M) to over 10GHz (3cm)

3. Troposphere
Troposphere is atmosphere from ground level to about 35,000 feet. It is the region where clouds are formed.

4. < http://www.cplus.org/rmw/english1.html > Atkins
Useful References
Dishman, QST, November 1961
SPLAT!
< >
On line at: < >
RadioMobile
< >
Atkins
< ml>
Rehr
< >
< NMVHF.org > and the NM VHF Society

5. Troposcatter from Inhomengenities

6. Density Inhomogeneities (Blobs) in Upper Atmosphere

7. Troposcatter Path Loss from Dishman QST, November 1961

8. Two Meter Path Loss as a Function of Distance

9. Loss very dependent on takeoff angle – Hills are nice

10. Relative path loss increases as frequency increases – offset by increase in antenna capture area

11. QSB is significant on Troposcatter

12. Tools to Calculate Path Loss
There is no first principles theory, all calculations are made with numerical constructs built to match observed data
can be big variation in results depending on whose technique you use
Calculations can be made by hand using troposcatter loss formulas – requires knowing distance to nearest obstruction on each end.
Visual Basic < >
Computer tools using Longley-Rice NBS model have terrain data built in and are much easier to use
Radio Mobile
SPLAT!
These are available in standalone or on-line versions
Online version recommended to start as gathering the terrain data can be daunting

13. Calculating Path Loss Capability with SPLAT!

14. Radio Mobile On-line Calculations

15. Using Radio Mobile Online Demonstration

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