1. Basic concept

Tuning as with transmit antennas (SWR and resonance) is not applicable.
The verticals in a 9-Circle RX array are electrically short and therefore broadband.
Balancing is essential: all antennas must deliver equal output so the combiner can operate correctly.
The goal is to make sure all 9 signals match as closely as possible in amplitude and phase.

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2. Preparation

Check all coax cables, connectors, and preamps.
Always use the same coax type and length for each element.
Install the verticals as mechanically identical as possible and avoid nearby obstacles.
Place a test beacon at about ±1 wavelength distance (for 160 m: ±160 m). A few watts of power is sufficient.

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3. Balancing procedure

Step 1 – Individual measurement

Connect only one antenna at a time to the center port of the combiner.
Receive the test beacon with an SDR or receiver (AGC disabled).
Record the signal level.
Repeat this for all 9 antennas individually.

Step 2 – Comparison

All antennas should be within ±1 dB of each other.
If the difference is larger, the affected antennas must be mechanically adjusted (extend or shorten) until reception is equal.

Step 3 – Final check

Connect all 9 antennas back to the combiner.
Test the array pattern:
Listen to the beacon while moving or rotating it → you should see clear directivity and deep nulls.
In practice, this can also be done with strong amateur stations on the band.

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4. Tips

Use an SDR with spectrum display for precise dB measurements.
Repeat the test regularly (e.g. yearly) to detect degradation in time.
Balancing usually only needs to be done once properly, unless something fails.
Remember: without balance there is no good pattern – this is more important than the exact position of the nulls.