Matched loss, the extra loss from a mismatched load, power at the load, and delay for RG-58, RG-174, RG-316, LMR-400, and semi-rigid. Every attenuation number comes from one manufacturer datasheet.
Coax loss
1.00 m at 2.40 GHz
LMR-400foam polyethylene
Matched loss
0.22 dB
Extra from VSWR
-0.00 dB
Total loss
0.22 dB
Power at the load
-0.22 dBm951.20 µW
Return loss at the input
∞ (matched)
Delay
3.92 ns
Electrical length
9.42 λ (3391°, 151° mod 360)
Fit a·√f + b·f. a = 0.1275 dB/m per √GHz, b = 0.008230 dB/m per GHz. Largest miss versus the sheet is 0.04 dB/100 ft at 150 MHz.
Cutoff frequency on the sheet is 16.2 GHz. That is not an attenuation rating. Loss is calculated only through the 8000 MHz row.
Fit a·√f + b·f. a = 0.8495 dB/m per √GHz, b = 0.09725 dB/m per GHz. Largest miss versus the sheet is 0.38 dB/100 ft at 1.0 MHz.
Attenuation is printed through 3000 MHz. 5.8 GHz is not on this sheet.
Belden 83284 technical data sheet, accessed 2026-10-11. Belden 83284, RG-316, PTFE, commercial non-QPL (M17/113-RG316). Z0 50 Ω, OD 2.5 mm, VF 70%.
LMR-400
Belden 83284
Tap or hover the curve for a readout. Each line stops at that cable’s last printed frequency.
What the loss number is
Each curve is a least-squares fit, a·√f + b·f, to the attenuation table on one manufacturer datasheet. a is the conductor term and b is the dielectric term. The fit is reported against those printed points, and it is not used past the last printed frequency. Matched loss is that attenuation times length, at 25°C and VSWR 1, which is how the sheets specify it. A load VSWR then adds the extra line loss from the ARRL expression. Power at the load is the power you type in, minus that total.
Why thin cable hurts at 2.4 and 5.8 GHz
RG-174 and RG-316 use a 26 AWG center conductor. RG-178 is 30 AWG. The RF current is already crowded into a thin skin, and a small wire has little surface to carry it, so the √f term is large. Belden’s RG-316 table reaches 2.4 GHz. Their RG-174 table stops at 1 GHz. LMR-100A is the small cable in this list with a printed 5.8 GHz row. A short jumper of any of those is often more loss than ten meters of LMR-400 at VHF.
Cables and sources
The part number is the part. “RG-58” on this page is Belden 8262, not an average of every cable that has ever used that name. Sheets were read on 2026-10-11.
Pick the manufacturer part, the length, and the frequency. The loss is the datasheet fit, a·√f + b·f, times the length. Belden 83284 (RG-316) prints 47.2 dB/100 ft at 2400 MHz, so 1 m is 1.55 dB. Times Microwave LMR-400 prints 6.8 dB/100 ft at 2500 MHz, so 1 m is 0.22 dB. The calculator does not fill in a frequency the sheet never printed.
Why does coax loss go up with the square root of frequency?
The center and outer conductors carry the RF current in a skin a few micrometers deep. That depth shrinks as 1/√f, so the resistance, and the conductor loss, rise as √f. The dielectric adds a second term that rises in proportion to frequency. The fit on this page is those two terms. At a few hundred megahertz the √f term is almost the whole loss. By several gigahertz the straight-line term is visible, especially on PTFE.
Why do thin cables like RG-174 and RG-316 lose so much at 2.4 and 5.8 GHz?
A thin center conductor is a small resistor, and skin effect makes it worse as frequency rises. Belden 83284 (RG-316, 2.5 mm jacket) prints 47.2 dB/100 ft at 2400 MHz, 1.55 dB for a 1 m jumper. Belden 8216 (RG-174) prints 34 dB/100 ft at 1000 MHz and does not print 2.4 or 5.8 GHz, so this page does not invent those numbers. Times Microwave LMR-100A, a 2.79 mm cable in the same size class, prints 64.1 dB/100 ft at 5800 MHz, 2.10 dB per meter. A Taoglas 2.5 mm RG-316 pigtail that does publish 6000 MHz prints 2.59 dB/m there. LMR-400 at that same 5800 MHz row is 10.8 dB/100 ft, 0.35 dB/m.
When should I use LMR-400?
Use LMR-400 for an outdoor or long feed where the run, not the connector, sets the loss. It is 0.405 in (10.29 mm) foam-polyethylene cable with 85% velocity. Ten meters is 3.79 dB on Belden 8262 (RG-58) at its 400 MHz row, 2.17 dB on Belden 9258 (RG-8X) at 400 MHz, and 0.89 dB on LMR-400 at its 450 MHz row. It is a poor bench jumper: the jacket is stiff, and a short RG-316 or SUCOFLEX assembly is the usual lab cable. LMR-400’s attenuation table stops at 8 GHz.
How does VSWR add loss on a coax cable?
A mismatched load reflects power. That reflection travels back through the lossy cable, so the cable dissipates a bit more than its matched loss. The extra term here is the ARRL expression: with matched loss ratio A = 10^(α/10) and ρ = (S−1)/(S+1), total ratio = (A² − ρ²) / (A (1 − ρ²)). On 10 m of LMR-400 at 450 MHz and load VSWR 2, the matched loss is 0.89 dB and the extra is 0.18 dB. The input return loss is better than the load return loss because the cable attenuates the reflection on the way back. This is not a full source-and-load mismatch cascade.
What are phase and delay on this page?
Delay is length divided by velocity factor times the speed of light. Electrical length is that delay times frequency, shown in wavelengths and degrees. It uses the velocity factor printed on the datasheet. The Taoglas RG-316 sheet does not print one, so delay stays blank for that part. The model does not add dispersion.