Selecting the right coaxial cable assembly (RG316/RG58 with SMA, N, TNC): a practical RF engineer’s lens

Published on 12/23/2025 • Updated on 12/25/2025

Selecting a right Coaxial Cable assembly is very important from test fixtures to inter connecting RF Blocks like Amplifier, Filters, Wave guides or just outdoor Antenna.  In this blog post we will discuss how to select among the most commonly available Coaxial Cable and various RF Connector based on application. 

When an RF path “mysteriously” fails excess loss, unstable phase, intermittent behavior under vibration, degraded sensitivity, the root cause is often not the RFIC or the antenna. It’s the cable assembly: the specific combination of coax type, connector interface, termination method (crimp/solder), and how it’s routed and handled. Below is a deep, application-driven way to select RG316 and RG58 assemblies with SMA / N-type / TNC connectors, with the same mindset you’d use in a microwave lab: control impedance continuity, minimize parasitics, and design for the environment and lifecycle.

1) Start from the system requirements (not the part numbers)

Before picking “RG316 vs RG58” or “SMA vs N”, reduce your requirement to five RF truths:

  1. Frequency band and allowable insertion loss
    Loss rises roughly with √f due to skin effect and dielectric loss, so a “good enough” cable at 100 MHz can be unacceptable at 2–3 GHz. For RG316, typical attenuation is about 38 dB/100 ft at 1 GHz and ~58 dB/100 ft at 3 GHz (vendor-typical values).
    RG58 is physically larger (often lower loss than RG316 for similar constructions), but variants vary (solid/stranded, foam PE, braid coverage, etc.), so always confirm the specific datasheet or MIL style.
  2. Phase stability / electrical length stability
    For phase-critical systems (beamforming, coherent receivers, tight timing), the more important metric is often phase change vs temperature and bending. Flexible cables (including RG316 and many RG58 builds) can exhibit measurable phase shift when flexed. If your application is phase-sensitive, enforce a routing rule: fixed bend radii, no repeated flexing, strain relief near connectors, and specify a cable construction intended for “phase stable” use (even if it costs more than commodity RG types).
  3. Mechanical environment and routing
    Vibration, repeated mating, tight bends, and pull loads destroy assemblies long before RF specs are violated on paper. Choose connector coupling (threaded vs bayonet), cable OD, jacket material, and strain relief accordingly.
  4. Shielding effectiveness & EMI susceptibility
    Braid coverage, foil + braid, and termination quality drive shielding. Poor braid termination is a common “invisible” fault that shows up as radiated susceptibility or noisy spectra.
  5. Power handling & PIM (Passive Intermodulation)
    High power or multi-carrier systems care about heating, corona, and PIM. Connector selection, plating quality, cleanliness, and torque become system-level parameters.

2) RG316 vs RG58: what you really trade off RG316 (small, flexible, high-temp capable)

Many RG316 variants use FEP (PTFE - family) jackets and are commonly specified to DC–3 GHz with high temperature capability (often up to ~200 °C depending on build).


Why engineers pick it: tight packaging, lighter weight, better temperature tolerance, decent microwave performance for short runs.
Hidden pitfall: higher loss per meter than larger cables; also easier to over-bend and damage the dielectric near the connector if the strain relief is weak.

RG58 (larger OD, generally lower loss than RG316, robust for general RF)

MIL-style RG58 (e.g., M17/28-RG58) is defined in the M17 / MIL-C-17 family and is widely used for general RF interconnect, often cited around DC to 1 GHz for many traditional RG58C/U constructions (though some modern variants claim higher).


Why engineers pick it: more mechanically robust, often lower attenuation than RG316 for the same length, easier handling in the field.
Hidden pitfall: bulk and bend radius; also “RG58” in the market can mean many non-identical constructions, don’t assume two RG58 spools behave the same at 1–3 GHz.

Selection heuristic:

  • If your assembly is short, inside equipment, needs tight bends, or sees high temperature → RG316 is often the safer default.
  • If your assembly is longer, field-routed, or sees more abuse/pull and frequency is modest → RG58 is often more forgiving.

3) Connector interface choice: SMA vs TNC vs N-type

Connector selection is not only “frequency rating”—it’s also mating robustness, sealing, torque sensitivity, and repeatability.

SMA (compact microwave workhorse)

SMA is commonly used from DC-18 GHz in standard practice, with higher-performance variants beyond that.
Best for: compact modules, lab gear, embedded RF, short jumpers, higher-frequency prototyping.
Watch-outs: SMA is small, misalignment, over-torque, and frequent mate/de-mate can damage the dielectric and center contact, producing intermittent VSWR spikes.

TNC (threaded BNC-style; rugged, weather-friendly)

TNC is typically cited up to ~11 GHz and is threaded (better vibration resistance than BNC).
Best for: mobile radios, outdoor enclosures, vibration environments where you still want a relatively compact connector.
Watch-outs: choose quality parts; cheap TNCs can have mediocre return loss above a few GHz.

N-type (larger, robust, excellent outdoors; high power capable)

Type N commonly supports 0–11 GHz, with extended designs reaching ~18 GHz.
Best for: outdoor RF, base stations, higher power, lower PIM needs, field serviceability.
Watch-outs: size/weight; also ensure the cable transition is designed properly—an N on a very small coax can be mechanically vulnerable without a good clamp/boot.

Quick application mapping

  • Bench-top microwave test leads / compact RF modules: SMA
  • Rugged systems with vibration: TNC or N (depending on size/power)
  • Outdoor, high power, low-PIM assemblies: N-type (often the first choice)

4) Crimp vs solder terminations: performance is in the craftsmanship

Crimp terminations (preferred for production and repeatability)

Crimping, when done with the correct die set and strip dimensions, tends to be more repeatable and mechanically robust than hand soldering. It also reduces thermal damage risk to dielectric and avoids wicking solder into braid (which can create a stiff stress riser that cracks under flex).

What matters most:

  • Correct strip lengths (center conductor, dielectric, braid exposure)
  • Correct die geometry for the ferrule and center pin
  • Full braid capture under the ferrule (360° coverage)
  • Pull-test or at least a mechanical tug check on every assembly

Solder terminations (useful for prototypes and some connector styles)

Solder can be excellent if controlled, but it’s easier to ruin RF integrity:

  • Overheating can deform dielectric → impedance bump → higher return loss
  • Solder wicking into braid creates a rigid section → flex fatigue
  • Flux residues can contribute to corrosion and (in extreme cases) nonlinear junctions (PIM risk)

Best practice: if you must solder, use controlled heat, minimal dwell time, RF-appropriate flux, thorough cleaning, and verify with a VNA.

5) Handling and routing rules that prevent “mysterious” Cable assembly failures

These rules are boring—and they save projects:

  • Respect minimum bend radius (especially near the connector back-shell). Most intermittent faults start at the cable/connector transition.
  • Add strain relief: boots, clamps, or tie-downs within a few centimeters of the connector.
  • Use proper torque on threaded connectors: under-torque can loosen under vibration; over-torque can damage interfaces (especially SMA).
  • Keep interfaces clean fingerprints, metal flakes, or moisture can degrade return loss and (for high-power/multi-carrier) raise PIM.
  • Limit mate/de-mate cycles: choose connector families and quality levels appropriate for your maintenance model.

6) MIL specifications: how to use them intelligently

For coaxial cable, the long-standing U.S. military framework is commonly associated with MIL-C-17 (and the M17 slash-sheet styles). M17/28-RG58, for example, appears in published MIL-C-17/M17 listings with defined construction and electrical limits.
For connector interfaces and interoperability, MIL-STD-348 standardizes RF connector interface dimensions (critical when you mix vendors).
For connector qualification and general requirements/testing, MIL-PRF-39012 is a key performance specification used across many coax connector families.

Practical takeaway:

  • Use M17/MIL-C-17 style control when you need predictable cable construction and environmental ratings.
  • Use MIL-STD-348 to reduce cross-vendor mating surprises.
  • Use MIL-PRF-39012 when reliability/qualification and consistent connector performance matter.

7) A experienced RF Engineer workflow for selecting and validating an RF Coaxial Cable assembly

If you want fewer surprises, do what RF engineers consider:

  1. Model the loss budget (length × attenuation vs frequency). Use vendor-typical attenuation curves for your exact cable variant.
  2. Choose connector family by environment (SMA for compact microwave, TNC for vibration, N for outdoor/high power).
  3. Specify termination method (crimp for repeatability; solder only with controlled process).
  4. Prototype and measure: VNA for S11/S21, then a gentle “flex test” while watching S11 drift. If performance changes with bending, it’s telling you the assembly is mechanically unstable.
  5. Lock down process: strip dimensions, crimp dies, torque spec, cleaning method, and inspection criteria.

If you tell SigmaRF your typical frequency range, cable lengths, indoor/outdoor use, temperature/vibration exposure, and whether phase stability or low-PIM matters, we can give a tighter, application-specific recommendation (including which connector family we would  standardize on for each product line and what acceptance tests to add). Call or eMail us today!

Also read article on Semi-Flexible Coaxial cable assembly

Recent Post