ARES/RACES Emergency Coax Repair

During a real emergency we will do doubt take much of our emergency 
equipment with us, including extra lengths of coax cable.  But in the 
event that every piece of coax gets damaged during the emergency, we 
need a method of repairing the coax.

In an emergency we may need to fix the coax quickly, but perhaps not 
permanently.  The method(s) I will describe here have been used by me to 
repair coax damaged by a small emergency of ours called Sandy.  She's 
a little mutt that decided she had nothing better to do than to chew 
through my RG-8X coax feeding a 80/40-meter dipole antenna.

The materials you should have on hand are: aluminum foil, small wire, 
and electrical tape.  Tools needed are: knife or coax stripper, wire 
stripper, wire cutter, and needle-nose pliers.

For a more permanent repair you will also need a soldering iron,
solder, RTV (preferably the electrical connection-safe kind),
heatshrink tubing (big enough to fit over the coax with fixes), and a
method to shrink the tubing (lighter, matches, or heatgun.)

The first task is to find or make a dry, safe place to make the 
repairs.  Getting water into the coax (normally it wicks into the 
shield) will ruin the coax.  It won't destroy the wire, but the 
dielectric value will change completely, thus changing the impedance 
value.  The coax will no longer have an impedance of 50 ohms and it 
will no longer match your antenna.

  Cut both pieces of coax back enough so you can find dry shield and
  have enough to work with, but as short as possible.  Once I find dry
  shield I cut about three inches of outer shield off the coax.

  If you have heatshrink tubing, put a piece at least five inches long
  on one of the pieces of coax.

  Push the shield back as far as possible on both pieces.

  Strip off about two inches of insulation from the center connector
  on both pieces.

  Twist the center connectors together so they make as good a
  connection as possible and the connection should be one inch long. 
  Snip off excess wire.  (If you have solder and tools, solder this
  connection.)  Cut all sharp edges or stray wire off.

  Place electrical tape over this connection.  Add enough tape so
  that this new center is as large in diameter as the normal center
  insulation.  (Try not to have tape overlapping the center wire
  insulation.  The fit between the tape and the insulation should be
  as close as possible without overlapping.)

  Make sure there are no stray pieces of wire protruding from the
  tape.  We don't want to have a short where we "fixed" the coax!

                     ARES/RACES Emergency Coax Repair


  Stretch the shield back over the center insulation and the fix.  
  There should be enough shield so that some of it overlaps.  Press 
  it down to be as close as possible to its former position.  
  
  Tape or heat shrink the tubing over the new connections and you are 
  done with the minimal emergency repair.

Optional, better connections:
  Wrap some extra wire around the shield from one end to the other and 
  solder the wire on each end.  Do not solder along the entire length 
  of wire, it is not necessary.

  Wrap some aluminum foil around the shield.  Wrap only enough to help 
  keep the shield close to the coax and try not to have excess 
  overlapping the normal coax.

  Before taping or moving the heatshrink tubing into place and 
  shrinking it, check the coax for a short or an open.  Once you are 
  sure everything checks out OK, continue on.

  If you placed heatshrink tubing over one end of the coax, slip it 
  over the join/fix.  Position it so there is at least one inch 
  overlapping the good insulation on each piece of the coax.  If you 
  also have RTV, you might first put some over the join and then slip 
  the heatshrink over it, or you could squirt some RTV into both ends 
  after positioning the heatshrink.

  If you have RTV and tape but no heatshrink, put some RTV all around
  the join at both ends of the fix.  Then tape from one end to the
  other in a spiral pattern.  If you will be hanging the coax
  vertically then make sure you start wrapping from the end closest
  to the ground.  At the top side, continue wrapping for about three
  inches past the coax join.  This will insure water will not be able
  to get into the coax.

For the fix I performed on my system, I noticed no change in the SWR
readings for most bands.  For the fix we tried on 1/29/97 at the ARES
meeting we did not solder any connection and we used only tape.  The
readings were identical from 2.5 MHz up to 146.0 MHz.  The only 
difference was a slight increase in SWR at 146 MHz.  (1.0+ to 1.1-)
This kind of a fix might cause more problems (reflections) at even
higher frequencies.

All other fixes, other than getting a new piece of coax long enough 
for the job, require hardware, solder, soldering iron, and other tools.

73 & good-luck
Phil Karras, KE3FL
AEC Carroll County, MD