The best upgrade may be moving the antenna

Take a look before taking a measurement

A range plot is partly a portrait of your surroundings. A wall on one side, a ridge on another and an open stretch of sky elsewhere can produce a very uneven result. FlightAware's setup guidance stresses antenna position and line of sight. It does not follow that every indoor station is useless, or that every rooftop installation is good. [1]

Start with a safe walk around the available locations. Sketch obvious obstructions by direction. Compare that sketch with actual reception over several periods. Do not climb onto a roof to improve an afternoon's experiment. Get suitable professional help for high or exposed mounting, and keep equipment and ladders well clear of power lines.

High aircraft and low aircraft are different tests

Imagine two aircraft on the same bearing. One is high above the landscape; the other is descending behind a ridge. A station can perform well on the first and lose the second. A single "maximum range" number conceals that distinction.

The horizon calculator illustrates the geometry of a smooth spherical Earth. It computes the distance between two ideal horizon points from their heights. It deliberately excludes terrain, buildings, radio refraction, receiver sensitivity and traffic. It is a model of geometry, not a prediction of your station's coverage.

Use it to understand why aircraft height changes the opportunity to receive a message. Do not use it to promise an airport a coverage footprint or to declare your antenna defective.

Measure useful coverage, not a lucky dot

Choose the job you care about. That might be low arrivals in one direction, ordinary traffic over your town, or dependable observations from a poorly covered area. Write the job in the notebook before comparing positions.

Try location A, then B, then A again with the same equipment and settings. Use comparable time windows and record traffic conditions. If B looks better only during the busy period, traffic is a plausible explanation. Repeat before drilling holes.

Count fresh positions in the sector and height band that matter to you. Keep local observations separate from MLAT results and remote inputs. A station that imports a network's contacts has not acquired a miraculous antenna.

Cable belongs in the experiment

A higher antenna may need more coax. Look up the actual cable's attenuation at the operating frequency and length, and add connector or accessory losses when specified. The loss calculator translates a power ratio in decibels into a power percentage. It does not translate cable loss directly into a lost percentage of range.

Before changing cable, check for loose connections, poor strain relief and unsuitable weather protection. Record what you changed. If you replace the antenna, cable, filter and receiver together, the result may be better, but you will not know which purchase earned its keep.

A mounting plan needs an exit plan

Make the station safe to power down and service. Protect outdoor connections according to their manufacturers' guidance. Consider wind, water, condensation, heat and the consequences of a detached cable. Ask a qualified installer about an exposed mast, grounding and lightning protection; a web article cannot assess your building.

When the installation is stable, photograph it for your own maintenance record. Make a separate public version that removes exact location, house details, keys and serials you do not intend to share. An interesting antenna photograph need not become a house-identification exercise.