Coax types
| Type | Loss | Notes |
|---|---|---|
| RG-58 | High | Thin, cheap, fine for short HF runs |
| RG-8X | Medium | Good compromise for portable use |
| RG-213 / LMR-400 | Low | The default for permanent runs |
| Hardline / LMR-600 | Very low | Long runs and UHF |
Loss rises with frequency and length. A run that is acceptable on 40 m may waste half your power on 70 cm.
SWR — what it actually tells you
Standing wave ratio measures the mismatch between the feedline and the antenna. Practical readings:
- Below 1.5:1 — ideal.
- Up to 2:1 — fine; almost all transceivers deliver full power.
- Above 3:1 — most solid-state radios fold back power to protect themselves.
- Very low SWR across every band on an antenna that should be resonant on one — suspect a lossy
feedline or a bad connection, not a great antenna.
High SWR by itself does not damage anything on a short low-loss line; it wastes power in the feedline and can trip the radio's protection.
Tuners
An antenna tuner does not tune the antenna. It presents the radio with a load it likes, while the mismatch continues out on the line. That is fine with low-loss coax and a modestly mismatched antenna, and wasteful with lossy coax and a badly mismatched one. A remote tuner at the antenna feed point avoids the problem entirely.
Connectors and weatherproofing
PL-259/SO-239 up to VHF; N connectors above it. Solder properly, then weatherproof outdoor joints with self-amalgamating tape over the connector and electrical tape over that. Water in coax is invisible, permanent and the most common cause of a station that "used to work".