Coaxial Cable (Coax)

Because it’s commonly used in radio work, every ham should be familiar with coaxial cable, often simply called coax.

Coaxial cable is most often used between the transceiver (or T/R switch) and antenna.  In this application coax acts as the feed line (AKA transmission line) to carry transmitted and received RF signals between the antenna and radio.  Other types of feed line can be employed but coax is used by many hams because it is easy to work with and readily available.


Coax  is a type of electrical cable that has an inner conductor surrounded by a tubular insulating layer, surrounded by a tubular conducting shield. Most coaxial cables also have an insulating outer sheath or jacket.  The term coaxial comes from the inner conductor and the outer shield sharing a geometric axis.


To be useful coaxial cable must be terminated with mating RF connectors.  An experienced ham may terminate their own coax; at greater cost they may purchase ready-made and tested assemblies.

coax ca assy  coax ca assy2

A wide variety of coaxial cable and assemblies are available with different characteristics. A quick summary of the important features:

  • Characteristic impedance
  • Signal loss
  • Power capacity
  • Diameter/weight
  • Flexibility
  • Environmental resistance

A seventh important characteristic of coax is velocity factor but that is a more advanced topic of lesser importance so we’ll simply mention it here.

Coaxial cable selection for each installation may be a compromise between features, requirements, and cost. The ham has to factor in what he needs or wants, what is available, and what it costs.

A quick look at these features of coaxial cable: Continue reading

Antenna Lightning Protection

Many hams have a VHF/UHF radio and antenna for local communication, especially if they are involved in EmComm.  Ideally you have an exterior antenna up high for best performance with your radio. The downside to that is that vertically-oriented VHF/UHF  monopole antennas are a juicy target for lightning strikes.  Basically, they look like a lightning rod.

Lightning Antenna

Lightning wants to go to ground and if the best path is through your antenna and feed line, your radio is likely to be destroyed.  And if you’re right near the radio when it happens, you might be injured, or a fire might be started by the lightning strike.  Bottom line, bad things can happen with an outdoor antenna during a thunderstorm.

W0ZUX lightning damage
Lightning damage in W0ZUX shack

Lightning protection is important to have.  There are numerous sources of arresters available, mostly for coaxial cable (feed line).  Some simple and cheap, others complex and costly.  How much is your radio and even your house worth to you?

Here are some commonly available coaxial cable lightning arresters:

Arrestor4     Arrestor3     Arrestor2

Even better than these stand-alone arresters with separate ground wires is to group them on a plate that is well-grounded.


Special ground rods with arrester mounting plates are available for this:


Common lightning arresters on your antenna feed line help only with minor stray lightning bolts.  A direct strike on your antenna cannot be stopped by a simple arrester; there is too much energy involved to dissipate.  The radio will be destroyed in such a case, along with possible damage and injury.

So what can you do to protect yourself and your radio from lightning?  In addition to using arresters the best way is to Continue reading