Quick Reference
RG400 Coaxial Cable
50 Ohm • DC – 6 GHz
RG-400 is a double-shielded, silver-plated PTFE coaxial cable built to MIL-C-17 specifications with a 0.195" outer diameter. Its construction mirrors RG-142 but with two braid shields for even greater shielding effectiveness. The standard cable for military and avionics applications requiring certified materials and traceable performance.
RG400 Attenuation
Signal loss in dB per 100 ft at standard RF frequencies.
| Frequency | Loss / 100 ft | Loss / ft | 6 ft | 25 ft | 50 ft | 100 ft |
|---|---|---|---|---|---|---|
| 100 MHz | 3.5 dB | 0.035 dB | 0.21 dB | 0.88 dB | 1.75 dB | 3.5 dB |
| 450 MHz | 7.8 dB | 0.078 dB | 0.47 dB | 1.95 dB | 3.9 dB | 7.8 dB |
| 900 MHz | 11.5 dB | 0.115 dB | 0.69 dB | 2.88 dB | 5.75 dB | 11.5 dB |
| 1.8 GHz | 17 dB | 0.17 dB | 1.02 dB | 4.25 dB | 8.5 dB | 17 dB |
| 2.4 GHz | 20 dB | 0.2 dB | 1.2 dB | 5 dB | 10 dB | 20 dB |
| 5.8 GHz | 34 dB | 0.34 dB | 2.04 dB | 8.5 dB | 17 dB | 34 dB |
RG400 Power Handling
Approximate maximum continuous power (CW) at 25°C ambient.
| Frequency | Max Power (W) |
|---|---|
| 100 MHz | 120 W |
| 450 MHz | 50 W |
| 900 MHz | 33 W |
| 1.8 GHz | 22 W |
| 2.4 GHz | 18 W |
| 5.8 GHz | 10 W |
Construction & Materials
Center Conductor
Silver-plated copper, 19×0.2mm
The center conductor carries the RF signal. Material and diameter affect DC resistance, skin effect losses, and overall attenuation.
Dielectric
Solid PTFE
The dielectric insulator separates the center conductor from the shield. PTFE dielectrics offer superior temperature stability and lower loss versus polyethylene.
Shield
Double silver-plated copper braid
The outer conductor provides the return path and shields the signal from external interference. More braid coverage means better EMI rejection.
Jacket
FEP
The outer jacket protects the cable from physical damage, UV, chemicals, and moisture. PTFE and FEP jackets handle higher temperatures than PVC.
Velocity Factor
70% (c)
How fast the signal travels relative to the speed of light in vacuum. Higher velocity factor means shorter electrical wavelength per foot — important for phased array and delay-matched applications.
Max Voltage
1400 VRMS
The maximum continuous operating voltage. Exceeding this can cause dielectric breakdown. Relevant for high-power transmitters and pulse applications.
Available RG400 Assemblies
Choose a connector combination to see pricing and order. All assemblies are hand-built and ship free within the USA.
SMA MALE to SMA MALE
From $10.99
SMA FEMALE to SMA MALE
From $10.99
RP-SMA MALE to SMA MALE
From $10.99
RP-SMA FEMALE to SMA MALE
From $10.99
N MALE to SMA MALE
From $11.49
N FEMALE to SMA MALE
From $11.49
BNC MALE to SMA MALE
From $11.99
MCX MALE to SMA MALE
From $10.99
RP-TNC MALE to SMA MALE
From $10.99
SMA MALE to TNC MALE
From $10.99
F MALE to SMA MALE
From $11.99
F FEMALE to SMA MALE
From $11.99
FME MALE to SMA MALE
From $11.99
FME FEMALE to SMA MALE
From $11.99
PL259 UHF Male to SMA MALE
From $12.99
SMA MALE to SO239 UHF Female
From $12.99
BNC FEMALE to SMA MALE
From $11.99
SMA MALE to TNC FEMALE
From $10.99
153 more configurations available on the RG400 page.
Frequently Asked Questions
What is the impedance of RG400?
RG400 is a 50 Ohm coaxial cable. All standard RF systems (antennas, transceivers, test equipment) use 50-ohm impedance, so RG400 connects directly without any matching network.
What frequency range does RG400 support?
RG400 is rated DC – 6 GHz. At higher frequencies, the attenuation per foot increases, so actual usable range depends on acceptable signal loss for your application.
How much signal loss does RG400 have?
RG400 has 3.5 dB of attenuation per 100 ft at 100 MHz, rising to 34 dB per 100 ft at 5.8 GHz. Use the attenuation table above to calculate loss for any specific length and frequency.
Are CoaxRF RG400 cable assemblies made in the USA?
Yes. Every RG400 assembly is hand-terminated and continuity tested at our US facility. We build each cable to order — nothing is pre-made or drop-shipped from overseas.
Can I order a custom length of RG400?
Yes. In addition to our standard lengths (1, 6, 25, 50, 100 ft and longer), we accept custom-length orders through the Cable Builder. Custom assemblies ship within 1–2 business days.