[TowerTalk] Hard line connectors

[Glenn A Biggerstaff]

Several people wanted more information about my homebrew connectors so
here goes. The auto junkyard near me had  a roll of  1 inch 50 ohm Hard
line and the owner 
knows I like unusual stuff so $20 later I owned several hundred feet .
The cable  has a  copper corrugated helical outer conductor and a copper
coated  3/8 inch inner conductor. The manufacturer is Cablewave Systems.
First you strip about  5 inches 
of the outer insulation  then remove  about  1 1/2 inches of the outer
conductor with a hacksaw or a Dremel Tool using a cutoff disk.  A tubing
cutter will work if the outer conductor is smooth . The slide a  3 inch
piece of 1 inch of 1 inch copper pipe over the outer conductor .Then you
take an empty 38 pistol shell and punch out the primer with a small punch
and solder it to the inner conductor .  Take a 3/8 inch piece of #12 or
#14 solid copper wire  and put it in the hole where the primer came out
and solder it in place. Then  solder a SO 239 panel mount connector to
the wire in the  pistol shell.Next slide the copper pipe up to the SO 239
and solder the pipe to the connector  and to the outer conductor .
Waterproof with your favorite method and you are done!
I  have done 12 of these and they all worked well ,I measured the swr
bump at 144 mhz. at  less than 1.1  to 1.
 A couple of caveats first make sure the primer is dead before you remove
it if it has been fired it will have a punch mark on the primer face from
the firing pin .DO NOT punch it out if it has a weak or none existent
mark. Second this technique will only work on copper or copper coated
conductors in and out unless you can develop a way to solder the copper
to aluminum or a mechanical method.
 The only problem that I had was a bad section of cable which is probably
 why it was in  the junkyard. At the suggestion of Chris NV1E I built a
very simple Time Domain Reflectometer from QST May 1989 and it works very
well for finding cable faults and impedance bumps. 73,Glenn N3HUV

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