HB3YAQLucerne
Link budget
Follow transmit power, gains and losses to the receiver.
HB3YAQ · Ajdin HadzicLearning to take awayhttps://hb3yaq.ch/en/tools/link-budget
View saved items →Only in this browser
Loading calculator …
Formula & context
Pr = Pt + Gt + Gr − L − FSPL; Reserve = Pr − Schwelle / threshold
Levels use dBm, gains dBi and losses dB. Additional losses may include both feed lines and known polarisation losses.
A worked example
Doubling free-space distance reduces margin by about 6.02 dB. Reducing cable loss by 3 dB adds 3 dB of margin.
Assumptions & limits
Receive threshold depends on mode, bandwidth and required quality. A positive calculated margin does not guarantee a link across unknown terrain.
Building a radio link budgetUnderstand the reasoning →From reading to experimenting
Link budget
Doubling free-space distance reduces margin by about 6.02 dB. Reducing cable loss by 3 dB adds 3 dB of margin.
Open example with starting values →Frequency: 145 MHz · Distance: 10 km · Transmit level: 37 dBm · Transmit antenna gain: 2 dBi · Receive antenna gain: 2 dBi · Additional total losses: 3 dB · Receive threshold: -110 dBmBack to the learning article →Then change exactly one value. Compare the result and use the formula to explain why it changes. The model limits below the calculator also apply here.