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Decibels and the VHF/UHF Link Budget

A link budget adds gains and subtracts losses in decibels so an operator can see whether antenna gain, cable loss, path loss or noise is limiting the contact.

VHF & UHF Fundamentals VHF/UHF Core Concepts Reviewed 2026-07-19
Quick Answer: A link budget adds gains and subtracts losses in decibels so an operator can see whether antenna gain, cable loss, path loss or noise is limiting the contact.

Why This Matters

Decibels let unlike gains and losses be combined without pretending catalog gain equals delivered system improvement.

This subject must be treated as part of a complete station: operator authority, frequency and mode, radio configuration, antenna, polarization, feed line, support, environment and operating practice. Improving one specification cannot compensate automatically for a mistake elsewhere in that chain.

Engineering and Operating Foundation

A link budget adds gains and subtracts losses in decibels so an operator can see whether antenna gain, cable loss, path loss or noise is limiting the contact. The useful question is not merely whether a signal is present, but which controlled conditions produced it and whether the result is repeatable. Frequency, mode, bandwidth, power, duty cycle, antenna orientation, height, cable type, cable length, weather and nearby objects should be recorded whenever they can affect the conclusion.

Field Procedure

  1. Step 1: List transmitter power.
  2. Step 2: Subtract cable and connector loss.
  3. Step 3: Add verified antenna gain.
  4. Step 4: Account for path and polarization.
  5. Step 5: Compare with receiver threshold.
  6. Step 6: Preserve margins and assumptions.

How to Evaluate the Result

  • Change one important variable at a time and restore the baseline before the next comparison.
  • Separate what was observed from what was inferred. Signal level, decoded quality, impedance, SWR, audio reports and error rate are different measurements.
  • Repeat the test. A result that cannot be reproduced should be recorded as provisional rather than turned into a general rule.
  • Use the lowest practical test power and preserve screenshots, analyzer files, photographs, radio settings and location notes.

Common Mistake

Adding claimed gain while omitting feed-line and polarization loss. This shortcut hides the limiting subsystem and can create an incorrect repair or operating conclusion.

Safety and Authority Boundary

Stop-work rule: Stop transmitting for arcing, smoke, hot connectors, damaged insulation, unstable supports, unexpected equipment resets, an RF burn, or any possibility of contact with utility wiring. Remove power before touching or moving RF components.

The operator remains responsible for current privileges, band plans, identification, interference avoidance, RF exposure and local requirements. For equipment limits, the newest manufacturer documentation controls.

Source and Freshness Note

This independent CKB article was reviewed on 2026-07-19. Its source authority is ARRL engineering references and current official operating guidance. It summarizes principles and procedures without reproducing protected source prose, tables or illustrations.

Freshness rule: Recheck after any regulatory, band-plan, repeater, satellite-status, firmware, product, compatibility or safety change. A saved memory, codeplug, frequency list or old article is never a substitute for the current primary source.

Related CKB Paths

Continue through VHF & UHF Fundamentals, then compare related antenna, feed-line, measurement, troubleshooting and safety articles. Product fit or connector similarity never proves electrical, RF, mechanical or complete-system compatibility.

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