Low-Smoke, Non-Halogen Coaxial Cables
Military Shipboard Qualifications

Military Shipboard Qualifications
Since the 1940s, MIL-C-17 has been the definitive specification for coaxial, triaxial and other high performance
radio frequency cables. Beginning in 1970, United States standards making organizations have been establishing safety requirements
for product flame retardance, and more recently, smoke, toxicity and corrosive off-gassing properties. With revision "G", MIL-C-17
adapts qualification tests for each of these characteristics, which assures the coaxial cable you select for your applications will meet
the minimum safety standards.
　

In 1993, per MIL-STD-454, the military began the process of inactivating the use of polyvinylchloride (PVC) radio frequency
cables, that were used in military weapons systems. A new series of cross-linked, low-smoke, non-halogen coaxial cables were qualified
to replace the older inactivated PVC versions.
　

Many of the requirements existent in the MIL-C-24640 and MIL-C-24643 multi-conductor, low-smoke shipboard cables specifications
were incorporated into revision "G" of MIL-C-17. Table I describes some of these added
requirements as well as typical testing results.
　

In addition to the products of combustion requirements, these cross-linked, low-smoke designs offer higher levels of abrasion
and fluid resistance, that are commonly required in many of todays naval shipboard environments.
Low-Smoke, Non-Halogen Coaxial Cables
　

Attenuation and Structural Return Loss
MIL-C-17 specifications require that attenuation and structural
return loss (VSWR) be completely tested by sweeping 22
different 50 ohm cables over the frequency band for which their
use is recommended. Variance in materials or in the manufacturing
process can cause periodic discontinuities along a length
of coaxial cable, which can introduce resonance peaks (spikes).
These spikes occur when the discontinuities or changes in
electrical characteristics are periodic and at half-wave
distances.
When impedance changes occur periodically, there are frequencies
in which all of the reflections are in phase, resulting in
a large reflected signal or VSWR of the cables and their connectors.
Periodic reflections can also cause substantial increase
in attenuation at the resonance peaks. In the past, it was very
unusual to detect these narrow band, high attenuation spikes,
when cables were tested for attenuation using the older MIL-C-
17D discrete frequency test procedure (generally at 400 MHz
and 3 GHz and also at 10 GHz for RG-214).
Now, however, M17/190-RG214 has continuous swept maximum
VSWR and attenuation requirements from 50 MHz to 11
GHz. The maximum VSWR is 1.15:1 (23 dB SRL) at 100 MHz
increasing to 60 dB/100 feet at 11 GHz.
Coaxial cables that do not require "full band" swept frequency
performance can be procured under separate part numbers
in an unswept version. The specifications sheets for these
unswept cables recommend that they not be used above 400
MHz. The user must decide which cables will best suit the situation
based on cost, application and potential for system growth
and improvement.

MIL-C-17 QPL Listing
Only qualified cables should be used for military contracts.
All manufacturers of MIL-C-17 cables must obtain qualification
approval for their cables. The qualified products are then listed
in QPL-17, which is updated periodically throughout the year.
Please note that all RG numbered cables have been cancelled
from MIL-C-17 and only cables with part numbers starting
"MIL/17" should be used for new military contracts. Since
　

Qualification Inspections MIL-C-17 Requirements Typical MIL-C-17(G)
Critical to MIL-C-17(G) Inspection Results
　

Flame Propagation (IEEE-383) 8 Foot Maximum Burn Pass
Acid Gas Generation 2.0 Maximum 0.20
Halogen Content .20 Maximum 0.06%
Smoke Index (NES 711) 25.0 Maximum 11.4
Toxicity Index (NES 713) 5.0 Maximum < 2.2
Weathering 75% Minimum Retention Pass
Abrasion Resistance 75 Cycles Minimum 175 Cycles
Tensile Strength 1300 psi Minimum 1800 psi
Elongation 160% Minimum 200%
Fluid Resistance 50% Minimum Retention Pass
Heat Distortion 30%Maximum 10%
there is no longer any control of "RG" specifications, many cables
on the market with RG designations may be completely different in
construction and performance.
　

Special Designs
Although MIL-C-17 covers a broad range of cable types, Times
can also provide technical assistance in designing specialized shipboard
cables to meet specific system parameters that cannot be met
with existing MIL-C-17 cables. Please contact our Engineering
Department for assistance with your specialized applications.