Coax Cable Loss Calculator

Yes, you can — with some caveats.

The impedance mismatch between 75Ω coax and 50Ω radio equipment creates a 1.5:1 SWR. This causes about 4% of power to be reflected — often acceptable, especially considering RG-6's advantages:

• Lower loss than RG-58 — RG-6 actually has less signal loss per foot
• Very cheap and available — Buy it at any hardware store
• Good shielding — Quad-shield RG-6 has excellent RFI rejection

Best uses for 75Ω coax:

• Receive-only antennas (SDR, scanner, SWL)
• Temporary/portable setups
• When used with an antenna tuner (the tuner corrects the mismatch)
• HF use where the loss difference is minimal

Avoid 75Ω coax for:

• High-power VHF/UHF (losses compound)
• Permanent installations (use proper 50Ω cable)
• When feeding into amplifiers or sensitive equipment

Connector note: RG-6 uses F-type connectors. You'll need F-to-SO239 or F-to-BNC adapters, adding potential failure points.

Size, loss, and cost are the main differences:

RG-58 (0.195" diameter)

• Thin, flexible, cheap
• Highest loss of the group
• Good for: Short jumpers, receive antennas, HF mobile
• Avoid for: Long runs, VHF/UHF

RG-8X / Mini-8 (0.242" diameter)

• Same connectors as RG-58, but lower loss
• Good balance of flexibility and performance
• Good for: Moderate runs up to 100ft on HF/VHF
• Popular choice for portable operations

RG-213 / RG-8 (0.405" diameter)

• The "standard" ham radio coax
• Significantly lower loss than RG-58
• Good for: Base station HF, runs up to 150ft
• Uses larger PL-259 connectors

LMR-400 (0.405" diameter)

• Modern low-loss design
• About 30% less loss than RG-213
• Good for: VHF/UHF, long runs, repeater sites
• More expensive but worth it for 2m/70cm

General rule: Keep total feedline loss under 1-3 dB depending on application.

Every 3 dB of loss cuts your effective power in half. For a 100W transmitter:

• 1 dB loss: 79W reaches antenna — barely noticeable
• 2 dB loss: 63W reaches antenna — acceptable for most uses
• 3 dB loss: 50W reaches antenna — like losing half your power
• 6 dB loss: 25W reaches antenna — significant problem

More strict for receive: On weak signals, feedline loss directly reduces your receive sensitivity. A 3 dB loss means you need signals twice as strong to copy them.

When loss matters less:

• QRP operations (you're limited anyway)
• Strong signal work (local repeaters)
• When antenna gain compensates

Yes — coax degrades, especially when exposed to the elements.

What causes coax to fail:

• UV damage: Sunlight degrades the jacket, causing cracks
• Water ingress: Water in the dielectric dramatically increases loss
• Connector corrosion: Moisture causes connector failure
• Physical damage: Kinks, tight bends, crushing
• Rodent damage: Squirrels and mice chew through cables

Signs your coax is failing:

• SWR increases over time (not just weather changes)
• Visible jacket damage, cracks, or discoloration
• Water dripping from connectors
• Cable feels stiff or crunchy
• Intermittent performance changes

Lifespan: Quality coax properly installed with weatherproofed connectors can last 15-20+ years. Cheap coax or poor installation might fail in 5 years.

Prevention: Use UV-resistant jacket, weatherproof all outdoor connectors with tape and sealant, create drip loops, support cable to prevent stress on connectors.

Both have their place — the answer depends on your application.

Foam dielectric (like LMR-400, RG-8X):

• Lower loss — air pockets reduce dielectric loss
• Lighter weight
• Higher velocity factor (~0.82-0.85)
• Downside: Water can wick through foam if jacket is breached
• Downside: Can be crushed if over-tightened or kinked

Solid dielectric (like RG-213, RG-58):

• More rugged — survives abuse better
• Water-resistant if jacket is damaged
• Lower velocity factor (~0.66)
• Downside: Higher loss than foam
• Downside: Heavier

Recommendation: For permanent outdoor installations, foam dielectric (LMR-400) with properly weatherproofed connectors is the best choice. For portable use or areas with potential physical abuse, solid dielectric is more forgiving.

Yes — high SWR increases total feedline loss.

When SWR is high, power reflects back and forth through the cable multiple times before being absorbed or radiated. Each pass adds loss.

Additional loss due to SWR:

• 1.5:1 SWR: ~0.1 dB additional (negligible)
• 2:1 SWR: ~0.2 dB additional
• 3:1 SWR: ~0.5 dB additional
• 5:1 SWR: ~1.0 dB additional

Important: This additional loss is multiplicative with the cable's base loss. A lossy cable with high SWR compounds the problem.

The good news: Below 2:1 SWR, the additional loss is minimal and usually not worth worrying about. Focus on keeping your base cable loss low.

Match the connector to your cable and frequency:

PL-259 / SO-239 (UHF connector):

• The "standard" ham connector
• Good for HF through 2m
• Not weatherproof without sealing
• Works with RG-213, LMR-400 directly; needs adapter for RG-58/8X
• Limit: Losses increase above 200 MHz

N-type:

• Superior performance at VHF/UHF/microwave
• Weatherproof when mated
• More expensive
• Required for serious 70cm and above work

BNC:

• Quick-connect, good for test equipment
• Common on VHF/UHF handhelds (via adapter)
• Not ideal for high power

SMA:

• Small, used on handhelds and SDRs
• Good for UHF and up
• Fragile — not for repeated connect/disconnect

The dB loss is the same regardless of mode. Cable attenuation is purely a function of frequency, cable type, and length. Whether you're transmitting SSB, FM, or FT8, the same percentage of your signal is lost in the cable.

What DOES change is the thermal stress on the cable. Cable power ratings are specified for continuous carrier (100% duty cycle). Different modes have very different duty cycles:

• FM, FT8/FT4, RTTY: 100% duty — continuous carrier while transmitting. Full thermal stress. FT8 at 100W heats your coax exactly like FM at 100W.
• CW: ~40% duty — key-down time depends on sending speed. Average heat is about 40% of peak power.
• SSB: ~20-25% duty — voice peaks hit 100W but average is much lower. With heavy speech processing/compression, this can rise to 40-50%.
• AM: 100% duty — the carrier is always on. Note: AM carrier power is 25% of PEP, so enter your carrier power (not PEP) when calculating cable heating.

Why this matters: A cable rated for 500W continuous can safely handle 500W SSB (average ~125W thermal load), but 500W FT8 puts the full 500W thermal stress on the cable. Many hams have damaged feedlines after switching from SSB to FT8 at the same power setting.

Sources: ARRL Handbook (duty cycle table), ARRL Antenna Book (feedline power handling), Times Microwave LMR power derating guidelines.

Often yes — but it depends on your situation.

When premium coax pays off:

• Long runs (100+ ft): Loss savings multiply with length
• VHF/UHF: Losses are much higher at these frequencies
• Permanent installations: Install once, use for decades
• Weak signal work: EME, satellite, weak DX
• Repeater sites: Where reliability matters

When cheap coax is fine:

• Short jumpers (under 10 ft): Loss difference is minimal
• HF only: Losses are relatively low regardless
• Portable/temporary: May get damaged anyway
• Receive-only: SNR matters but isn't critical

Cost perspective: LMR-400 costs about 2x RG-213, but lasts just as long and gives 30% less loss. Over 20 years of use, the cost difference is negligible. Your antenna installation labor costs far more than the cable.

Recommended ham radio retailers:

• DX Engineering — Excellent selection, quality house brands (DXE-400MAX), good tech support
• Ham Radio Outlet (HRO) — Wide selection, multiple locations, competitive pricing
• Gigaparts — Good prices, fast shipping
• R&L Electronics — Been around forever, reliable
• SteppIR — Quality LMR and Times Microwave cables

Direct from manufacturers:

• Times Microwave — The original LMR manufacturer (timesmicrowave.com)
• Belden — Industrial quality, buy through distributors like Mouser or Digi-Key

General retailers (buyer beware):

• Amazon — Hit or miss. Stick to name brands (Times Microwave, Belden). Avoid no-name "LMR-400 equivalent"
• eBay — Good for surplus/used hardline. Be cautious of counterfeit LMR
• Home Depot/Lowes — Only for RG-6 cable TV coax

Pro tip: Buy pre-made cables with connectors for short runs. For long runs, buy bulk and learn to install connectors yourself — you'll need this skill for repairs anyway.

Top-tier manufacturers (buy with confidence):

• Times Microwave — The original LMR manufacturer. LMR-400, LMR-600, etc. The gold standard for low-loss coax.
• Belden — Industrial/broadcast quality. Makes 9913, 9258, and many others. Trusted for decades.
• CommScope/Andrew — Makes Heliax hardline and professional-grade cables. Used by commercial sites worldwide.

Quality ham radio brands:

• ABR Industries — Quality cables and assemblies, popular with hams. Good value.
• DX Engineering (DXE) — Their house brand (DXE-400MAX, DXE-213) is excellent quality, often matches or beats name brands.
• Davis RF — Makes Bury-Flex (direct burial) and other ham-specific cables. US-made.
• The Wireman — Been around forever. Known for antenna wire but also sells quality coax.
• MPD Digital — Authorized Times Microwave reseller on Amazon. Genuine LMR cables with good quality control.

Acceptable alternatives:

• Shireen — Makes "LMR-equivalent" cables. Not Times Microwave, but decent quality for the price.
• PCT/PPC — Quality RG-6 for cable TV applications.
• Amphenol — Better known for connectors, but their cable assemblies are excellent.

Brands to avoid or be cautious with:

• No-name Amazon/eBay imports — Often mislabeled specs, poor shielding, CCS center conductors
• "LMR-400 equivalent" or "LMR-400 type" — If it doesn't say Times Microwave, it's not real LMR
• Tram, GMRS brands — Often rebranded cheap imports

Pro tip: When in doubt, check if the cable has the manufacturer's name and specs printed on the jacket. Quality manufacturers mark their cables.

Key specs to check:

• Center conductor: Solid copper is best. Copper-clad steel (CCS) has higher loss but is cheaper and stronger for direct burial
• Shield coverage: 95%+ braid coverage for good RFI rejection. Dual/quad shield for noisy environments
• Velocity factor: Important if you're making matching sections (0.66 for solid PE, 0.82-0.87 for foam)
• Jacket type: PVC is standard. PE (polyethylene) is better for direct burial. UV-resistant for outdoor runs
• Loss specs at YOUR frequency: Loss at 1 GHz means nothing if you're on 40m

Red flags to avoid:

• "LMR-400 equivalent" or "LMR-400 type" — Often inferior knockoffs
• Unusually cheap prices — Probably CCS center or poor shielding
• No brand name or specs — If they won't tell you, there's a reason
• Aluminum braid — Copper braid is better (aluminum is cheaper but harder to solder)

Quality indicators:

• Printed specs on jacket (manufacturer, type, date code)
• Consistent diameter throughout
• Braid that doesn't unravel easily
• Clean, round center conductor

PL-259 / SO-239 (UHF connectors) — The ham radio standard:

• Amphenol — The gold standard. Silver-plated, precise machining. Worth the extra cost for permanent installations (~$3-5 each)
• Times Microwave — Excellent quality, designed for their LMR cables
• DX Engineering — Good quality house brand
• Avoid: Generic imports under $1 — poor plating, loose fit, early failure

N-type connectors — For VHF/UHF/microwave:

• Amphenol — Again, the best choice
• Times Microwave EZ-connector — Easier to install, good quality
• Pasternack — Professional grade, excellent specs

Connector types by cable:

• RG-58, RG-8X, LMR-240: Use reducers/adapters with PL-259, or specific crimp connectors
• RG-213, RG-8/U: Standard PL-259 direct fit
• LMR-400, Belden 9913: Specific connectors — don't use RG-213 connectors!
• LMR-600: Requires LMR-600 specific connectors

Installation types:

• Solder-on: Traditional, permanent, requires skill. Best for PL-259.
• Crimp-on: Fast, consistent, requires proper crimp tool ($30-100). Great for N-type.
• Compression: Common for RG-6/F-type. Requires compression tool.
• EZ-Connectors: Easier to install, good for LMR cables. Slightly more expensive.

Pro tips:

• Buy connectors matched to your specific cable — "universal" often means "fits nothing well"
• Get a few extra — you'll mess up the first one or two
• For outdoor use, always weatherproof with self-amalgamating tape + electrical tape
• A proper crimp tool pays for itself in reliability

HF Base Station (under 100ft run):

• Budget: RG-8X — Good balance of loss, flexibility, cost
• Better: RG-213 — The traditional workhorse
• Best: LMR-400 or Belden 9913 — Lower loss, worth it for long runs

VHF/UHF Base Station:

• Minimum: LMR-240 for short runs (<50ft)
• Recommended: LMR-400 — Significantly lower loss than RG-213 at 2m/70cm
• Best: LMR-600 or hardline for long runs or weak signal work

Mobile installations:

• HF mobile: RG-8X or LMR-240 — Flexible, manageable in vehicle
• VHF/UHF mobile: LMR-240 — Best balance for short runs in vehicles

Portable/Field Day:

• HF: RG-8X — Light, flexible, handles abuse
• VHF: LMR-240 or RG-8X

Short jumpers (under 6ft):

• RG-8X for HF
• RG-174 for SDR/receiver connections (accept the loss for convenience)
• LMR-240 for VHF/UHF

Repeater/Commercial:

• Standard: LMR-400 or LMR-600
• Best: 7/8" Hardline — Lowest loss, longest life

The proper method (do ALL of these):

1. Start clean: Make sure connector is properly installed and tight
2. Self-amalgamating tape (Scotch 23 or similar): Wrap tightly, stretching 50% as you go. Overlap 50%. Cover entire connector plus 2" of cable on each side.
3. Electrical tape: Wrap over the self-amalgamating tape for UV protection and extra sealing
4. Optional: Coax-Seal or silicone: Additional protection at cable entry points
5. Drip loops: Always create a loop below the connector so water runs away, not into it

Products that work well:

• 3M Scotch 23: The gold standard self-amalgamating tape
• Coax-Seal: Moldable sealant, great for irregular shapes
• Permatex Dielectric Grease: Prevents corrosion inside connectors
• PlastiDip: Spray-on weatherproofing (removable)

What NOT to do:

• Don't use only electrical tape — it fails in UV and doesn't seal
• Don't use silicone caulk directly on connector — impossible to service later
• Don't skip the drip loop — water WILL find a way in
• Don't assume "outdoor rated" connectors don't need weatherproofing — they do