Start here: A 450-ohm ladder line has roughly 450-ohm characteristic impedance; the impedance presented at its input changes with antenna impedance, frequency, line length, and velocity factor.
What the operator is actually controlling
The label describes a transmission line, not a fixed load. A mismatched line transforms impedance as electrical length changes, so the tuner can see high resistance, low resistance, or large reactance on different bands.
Use this sequence
- Record the exact line type and physical length.
- Estimate electrical length using the manufacturer velocity factor.
- Evaluate the full antenna and line at each operating frequency.
- Change line length only deliberately and record the result.
Do not make these substitutions
- Entering 450 ohms as the antenna load on every band.
- Cutting line from one favorable reading.
- Assuming low-loss ladder line removes tuner voltage and current stress.
URT1 boundary
CHA URT1 User Guide 260524 and Applications Guide 260612. The current guide controls; direct ladder-line use is not presented as a supported URT1 connection.
