Cable X-Perts, Inc.

Coax Cable Calculator & Guide

In order to get the best performance from your transceiver and antenna system, you should use the appropriate coax cable. However, that does not imply the most expensive cable, or necessarily the cable with the lowest attenuation below 30MHz. For there are intricate factors to consider, and to help you make the appropriate cable decision use this handy
Cable Calculator Guide:

(This is intended to be used as a general guide only.)

Length of cable run:
Operating Frequency:
Power Range:
Impedance:
Antenna System Type:
With Connectors Installed: YES NO

In addition to the Cable Calculator Guide results, also read the examples listed below. You need to consider that there may be some variations to your antenna system(s) and it would be unworkable for our guide to address all those systems.

Example 1:
If you’re operating a 10, 15, & 20 meter tri-bander or multi-band vertical antenna system with a high watt amplifier, and your "run" is around 50ft-250ft, then RG213/U is typically the appropriate cable to use. Because typically these antennas work consistently well with a 50 Ohm cable using a solid Polyethylene Dielectric rated at 66% Velocity of Propagation. Similarly, Solid Polyethylene Dielectrics tend to maintain their electrical integrity over a longer time period, even at constant high-wattage.
Example 2:
If you’re operating a multi-band vertical antenna or a dipole antenna system below 30MHz and without an amplifier, and your "run" is from 100ft to 300ft, then RG8/U with a foam Polyethylene Dielectric is typically the appropriate cable to use. This Dielectric is rated 78% Velocity of Propagation. In this case, since there is no amplifier, the foam Dielectric will not be adversely affected. Yet, you enjoy slightly lower attenuation.
Example 3:
If you’re operating 2 meter &/or 440 antenna systems, the lower attenuation 50 Ohm coax cables are definitely appropriate to use here, regardless of the cable "run". These cables are 9913 flexible, The Times Microwave LMR® series, and/or Andrew Heliax®. They operate with a Velocity of Propagation of 84% or higher and all have either a double or corrugated shields. Since the higher frequencies have greater losses, and require greater shielding, these cables offer the best overall performance characteristics.

For additional guidance use our Attenuation & Power Rating Coax Chart. The Times Microwave LMR® series and the Andrew Heliax® are both listed separately.

In closing, it is essential that connectors are properly terminated, installed and that your antenna is resonant. Otherwise, the cable(s) may not perform as specified.


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