Probably the best DX site in the world
 DX news
Homemade CATV connectors

By George Dowell, K0FF
November, 2000

Often 3/4" CATV aluminum feedline is free for the taking. Not so the connectors, at least any that would be at home in the typical Hamshack. Here is a way to make weatherproof splices and connectors s at little cost with readily available parts. All materials used are made of aluminum, so there is no problem with dissimilar metal corrosion.

First we look at the parts needed to make a reliable splice, and the preparation required:
In the back-ground is the shield splice. It is made from a 1/2" he avy wall (threaded) aluminum conduit coupler. Inside are female threads that are made to screw onto the male threaded conduit. Try a piece of your cable for fit. It needs to be just loose enough so that it slides back and forth over the coax shield. If it s too tight, simply file the points off the threads with a round file until a perfect fit results. Drill 8 11/64" holes equally spaced around the periphery, 1/4" back from the edge. You can see the paper template that I used to assure symmetrical hole patterns.
In the foreground is the center conductor splice component. It is simply a 1/2" long piece of 1/4" copper water supply tubing that has two 3/32" holes drilled in the side for soldering. Typical of the material used to connect water to an icemaker.
Dielectric insulation saved from the preparation of the cable is fashioned into two sabots that will be inserted into the gap in a later step, minimizing the impedance bump.
A set of eight 3/8" , #8 aluminum self tapping screws completes the parts list. The points are ground off flat. Start with a 1/16" drilled pilot hole, start threads with a pointed screw, then remove and replace with a flat end scew.
Prepare the coax cable by stripping the shield and dielectric back, leaving a squared end on the center conductor that extends 1/4".

Assembling the Splice. Solder the copper tube between the prepared center conductor ends.
Step 2: Insert the prepared dielectric plastic into the gap.

Step 3: Slide the coupler over the gap and secure with #8 aluminum screws.
Step 4: Apply a little Silicone Grease to the Joints . Note: not Silicone Adhesive.

Wrap entire joint with a few layers of Scotch 33+ and a few light coats of Krylon Clear over that will assure a weather tight seal.

Comment from the pro:
Your CATV aluminum splice has at least one major problem and that is impedance mismatch.
The distance between the center conductor and the shield (aluminum tubing) which is separated by the dielectric is what determines the impedance of the cable. Your idea changes this dimension and as a result changes the impedance.

The "Splice" also will cause serious mismatch which will reduce the return loss or VSWR of the cable causing potential problems.
A $10.00 splice is not only worth it, it is much easier to install. We can supply any splices of connectors for CATV cables

BJ Toner, Toner Cable Equipment Inc.
21 February 2001

Front page
DX News
Andes DX
DX Lab
In Print
Web Stories

Web Archive
Mail Archive

Search all HCDX
mail since 1995

 About us
About us
Write to us

HCDX mail list

antennX  Cebik  FM antennas  Werner's links  Antenna Elmer  Coax basics