The Release Margin: An Additive dB Ledger
Ada re-adds the chapter’s link-budget ledger in decibels to find the release margin
ADA · CALCULATION AUDIT
The Release Margin: An Additive dB Ledger
The physics question is simple: after the signal spreads, hits the site losses, and reaches the receiver, how much verified headroom is still left? The chapter’s example launches 14 dBm, adds antenna gain, subtracts 96 dB of path loss and 15 dB of site loss against a -118 dBm receiver, then reserves 10 dB. This audit re-adds that ledger in decibels to find the release margin.
Companion to the chapter Link Budget and Coverage Planning — every number here comes from that chapter.
The example ledger, added and subtracted in dB
The example in this chapter uses values already named above: 14 dBm launched power, 2 dB of antenna-path gain, 96 dB of path loss, 15 dB of site loss, a receiver sensitivity of -118 dBm, and a 10 dB reserve requirement. Because all gains and losses are in dB, the link budget is addition and subtraction.
| Step | Calculation | Result |
| Received power | 14 + 2 - 96 - 15 | -95 dBm |
| Nominal margin | -95 - (-118) | 23 dB |
| Reserve paid | 23 - 10 | 13 dB release margin |
Check the arithmetic: subtracting a negative sensitivity adds the receiver headroom, so -95 - (-118) = 23 dB. The design then spends 10 dB on the promised reserve, leaving 13 dB. That positive release margin supports field validation; it does not remove the need for representative RSSI or SNR measurements after installation.
Every number above is taken from the chapter’s own link-budget example and re-derived step by step.