New ADS-B Systems Bring Coaxial Demands: RG58 VS. RG400

| Amanda Kole

A recent Avionics News Article highlighted the need to upgrade coaxial cables from RG58 to M17/128-RG400. Aircraft are currently upgrading to Automatic Dependent Surveillance-Broadcast (ADS-B), which the FAA is calling the “hallmarks of NextGen surveillance.” Implementing the new technology helps determine the position, traffic, weather, and other related flight-information used for air-traffic control.

Beginning January 1, 2020, all aircraft that fly within most controlled airspaces must be equipped with an ADS-B system, and as such upgrades to these new requirements have begun. The transmit power on a new system is a significant increase compared to the older Mode C transponders, making it necessary for the coaxial cable enhancement. New ADS-B systems need the insertion loss on the cables reduced to 1.5 decibels or less versus the older models which could operate on an insertion loss of 2.5 decibels or higher. Due to the change in requirements, M17/128-RG400 coax is set to be the new coax cable of choice and will be in high demand as the new transponders are installed. 

Harbour Industries is a major supplier of the QPL certified M17/128-RG400 Coax cables that WireMasters stocks so our team reached out to get their input on these new upgrades.

 “No doubt the FAA’s requirement that virtually all aircraft will need ADS-B Out compliancy by 2020 is a very big deal.  Aircraft flying without an ADS-B Out may be denied access to airspace” said Trum Rittling, Director of Sales for Aerospace Cables at Harbour.  Rittling continued, “Often cables are the last consideration of avionic system installers, but without the proper upgrade to M17/128-RG400 the system will simply not work!”

Prior to ADS-B, RG58 was often the coax cable of choice. You can find a comparison chart of the RG58 Coax and the M17/128-RG400 coax below in our infographic. Weight savings is always a topic of discussion within the aviation industry, and the RG58 is the lightweight option. However, you will notice that the temperature ratings of the M17/128-RG400 exceed well beyond those of the RG58. Its high-temperature rating is part of what makes the M17/128-RG400 such a high-performance cable. ADS-B transponders require these high-performance cables and demand maximum signal transfer speeds, which is where the Velocity of Propagation(VoP) rating plays a part. With a 69.5% VoP offered on the RG400 vs. 66% VoP on the RG58, the signals can travel through the constructed cable at a faster speed using the RG400.  The signals travel also depends on the attenuation and frequency ratings. As you notice in our chart below, the RG400 has a maximum frequency of 12.4 GHz compared to a 5 GHz using the RG58. The stranding on the RG400 Silver Covered Copper conductors allows for a higher attenuation rating, therefore, gives a higher maximum frequency and over a longer distance. 

Both coaxial cables fall under the MIL-DTL-17 / MIL-C-17 military specifications. Cables covered by this specification are primarily intended for use as transmission lines to conduct energy in a simple power transfer continuously or intermittently. For the QPL listings for these specs CLICK HERE.

If you need further guidance about the M17/128-RG400 or RG58 coax products, contact our sales team at [email protected] or 1.800.635.5342. Also visit our RG400 product page to a request a quote-CLICK HERE.

To view the complete Avionics News Article we mentioned CLICK HERE