Need Confirmation on my Calculation of DB Loss?

Question

If the equation to figure out DB loss is L = 20*Log10(4*π *d) / λ

L is the path loss in decibels, λ is the wavelength (for instance meter), d is the distance between the transmitter and the receiver (for instance meter).

λ = 36.19/ft (434.28/inches)
d = 20 Miles
π (Pi) = 3.141593


In my calculation, I'm getting a DB Loss of 138.89/db. Can anybody confirm this
or is my answer completely way off the mark? I think my entering of 20 Log10 into
the calculator might be at fault. Not sure..

My overall goal is trying to find out the db loss on a CB radio broadcasting on
Channel 19 (27.185 Mhz) at 60/Watts. Some pre-calcs have yield that my 60/Watts is
about +48/db and a normal CB can receive at around -113/db. So that means if I'm broadcasting
at +48/db and somebody is receiving at -113/db, how far away can they be (under ideal settings)
to receive my transmission before 161/db is loss in the ether?

Answer 1

d and lambda should be in the same units. With your units, I get lambda = 11.03 m and d = 32187 m, so the loss is 20*log10( 4*pi*32187/11.03) = 91.3 dB.



By the way, your use of a slash is a little confusing. 36.19 ft shouldn't be written as 36.19/ft, it looks like feet is in the denominator. Same for 60/Watts, -113/db, etc.

Answer 2

Its not a formula I'm familiar with, but make sure your units are the same. I would think that d and λ both need to be either in feet or in miles, but not some of both.

With that in mind, I tried it and got about 60.

Answer 3

HI ALBY.

HOLLEY-MOLE'LY!, CB'S ?, I THOUGHT THIS FORM OF TRANSMITTERS FINNISHED IN THE 70'S AND EARLY 80'S.



HERE IN N.Z WE HAVE ACCESS TO "HAM FREQUNCY RADIO'S", WHICH USE ....YAESU OR UNIDEN TRANSMITTERS WHICH THE BRORDCAST RANGE CAN BE VAST....LIKE HUNDREDS OF MILES.



IN LESSOR STRENGTH MACHINES WE USE UNIDENS THAT CAN BE GOT FROM OUTDOOR STORES WHICH HAS A RANGE BETTER THAN THE CB'S. IF THE RANGE NEEDED TO BE EXTENDED? AN REPEATER CAN BE GOT FROM UNIDEN.





CHEERS CARL G