Another satisfying Ham Radio project. Again, thanks to plumbing....if it
wasn't for plumbing we hams would be in a fix after all we are all full
of.........
We were very fortunate to have had a long time ham friend donate lots of CATV
hardline drops to the W1CW contest station effort. Like any good contest
station, there are lots of antennas, and lots of antennas need lots of
feedlines...lots of feedlines need 2X lots of connectors.
Over the past two years "plumbers delight" connectors for the hardline have
been developing. The initial versions were some our friend had whipped up and
some taken from a hint and kink seen in QStreet, if memory serves it was from
K1DG.
All the antennas, switches etc, are always looking for a PL259 to mate with
them. Rather than reinvent the wheel, adapting the PL259 to the hardline has
seemed the way to go. The previous version of the W1CW connector was based on
a 1/2" compression compression union fitting - a double female.
The OD of the hardline's aluminum shield is half inch - so a good size match
was found there, and the OD of the back end of a PL259 is 1/2". By leaving a
long center conductor protruding from the end of your hard line you could
pass it through the double female connector and then into the PL259. Once the
tip was soldered in place you simply worked away from it compression fitting
wise. First you tighten one end of the dbl-f onto the PL259's tail end - the
part that has the inner threading which normally screws onto the
RG213/whatever. Then, tighten the other end of the dbl-f onto the aluminum
shield of the hardline. Done. The only drwaback of this generation of fitting
has been the bulkiness of this approach, and inherent lack of mechanical
strength since the point where the shield is grabbed is three or so inches
back from where you twist the PL259. This version has worked well for us, but
today I made something even slicker.
In the plumbing department at Home Depot I found a series of "universal"
compression fittings designed for all type of tubings. The fittings are
designed for say rubber or plastic tubing, as well as copper. The come with
inner sleeves for the softer tubes so that when the compression fitting is
cinched down the tubing won't collapse.
The particular fitting I used, although I am sure it is a generic thing
available from many manufacturers was an Anderson Barrows #A-209 Tube to Tube
Reducing Union With Inserts.
This particular fitting was an adaptor for going from 1/2" to 3/8" tubing. I
only used the 1/2" inch side of the fitting and threw the other parts
away....it may be possible to find another fitting which does not have the
expense of the 3/8" fittings on it, however the Home Depot I was in only had
this one style.
First, after removing all the nuts and sleeves, I cut the connector in half,
keeping everything from the central flatsided area where your crescent wrench
grabs hold on over to the 1/2" end of the fitting. This gave me the part to
anchor to the hardline, so I was half "done"....now how to attach this to the
PL259?
After cutting it in half, the central part of the fitting had a hole about a
1/4" in diameter where the water would have flowed through the coupling. I
then drilled out this hole on the drill press up to a 1/2" diameter....go
slowly, do this in several bit size steps, that soft brass and it is really
easy to get a drill bit stuck in.
The 1/2" inch hole allowed the butt of the PL259 to slid up into it. The fit
was tight, but with just a tiny muscle the PL259 slid on in. I stopped shy of
the PL259's outer shell hitting the brass fitting by about 1/8" inch.
With the PL259 pointed tip down, I came in from the back side of the fitting
with the mac-daddy grande mega soldering iron (it is a big ole plumbers
soldering iron) and proceded to heat things up. A torch would have worked
here too - but I couldn't find it, hi.
I soldered the PL259 to the plumbing fitting, once the fitting got hot it
slightly expanded and the solder flowed nicely between the outside of the
PL259 and the 1/2" hole. The compression plumbing fitting and the PL259 are
now married for life.
This resulted in a connector which is only about half or three quarters of an
inch longer than a PL259. Way shorter than that old kluge (spelling?) of the
double compression fitting.
By removing about an inch and three quarters of the aluminum shield but only
removing about and inch of the foam dialectric the 3/4" of an inch of "extra"
foam sticking past the aluminum shield will thread up into the PL259, just
like the threading you normally do onto a piece of RG-#.
This fitting is small and sturdy, I feel it is the answer I have been
looking for to turn the priced-right CATV drops into QSOs. Now it is time to
design some more antennas to take advantage of my new find.
Oh yes, the cost. The fitting was $2.23 plus tx, and a PL259 is around a buck
or so depending on what grade you buy. So, that's roughly three fifty - a lot
cheaper than a commercial connector...a REAL lot cheaper. I made up four of
these in an hour and a half....they were protoypes, the next batch will
probably take ten or fifteen minutes each tops....If I mass produce a bunch
of them it will be even quicker. I will try and remember to put one of these
in my pocket and bring it to Dayton with me. Look out airport security, he's
carrying a sawed off PL259!
Jim zx k1zx@contesting.com
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