Calculating loss in Transmission line

[Radio Bob]

It's been while. If you have a transmission line 125 feet long with an attenuation of 4.74 db/100m at your operating frequency what percentage of efficiency should you expect out of the line? Thanks in advance

 

[Kelly A]

It's been while. If you have a transmission line 125 feet long with an attenuation of 4.74 db/100m at your operating frequency what percentage of efficiency should you expect out of the line? Thanks in advance

All the manufacturers publish the loss at distance for their transmission line types. You should determine the loss/efficiency at frequency range of the line using their published specs. If you're starting from scratch:

Cable loss = K1 x sqrt(F) + K2 x F (dB/100 feet)
Where:
K1 is the resistive loss constant.
K2 is the dielectric constant.
F is the frequency in hertz (Hz)
Cable loss consists of resistive loss, dielectric loss, and connector loss. In the equation, K1 represents resistive loss and relates to the square root of frequency; the dielectric loss in K2 relates to the signal’s frequency and connector loss relates to connectors used.

 

[rfry]

... If you have a transmission line 125 feet long with an attenuation of 4.74 db/100m at your operating frequency what percentage of efficiency should you expect out of the line?

For those conditions, a line that is 125 feet (38.1m) long would have a total attenuation of 38.1/100 x 4.74 dB = 1.806 dB.

Efficiency for 125 feet of line assuming a load SWR of 1:1 = 1/[10^(1.806/10)] = 0.6598 = 65.98 %,

 

[Radio Bob]

Thanks

For those conditions, a line that is 125 feet (38.1m) long would have a total attenuation of 38.1/100 x 4.74 dB = 1.806 dB.

Efficiency for 125 feet of line assuming a load SWR of 1:1 = 1/[10^(1.806/10)] = 0.6598 = 65.98 %,

Thanks