Fw: [Antennas] Splicing Coax

[George, W5YR]

Merv, we have a lot in common in our backgrounds in ham radio. 

I started with a 25 watt bulb and later graduated to a monster 250-watt
bulb  for tuneups. My first station in 1946 used on of the big surplus
knife switches (remember those? Brand new in the box for $0.25!) to switch
300-ohm TV twinlead from the receiver to the transmitter. Wore my arm out
reaching around and "throwing the big switch."

I, too, have spliced coax in much the same fashion as you describe. But we
differ on a couple of points which I think are significant.

First, I always just butt-join the center conductors keeping them aligned.
A healthy but modest buildup of solder around the joint adds strength. The
poly plug then fits around the wires and keeps them aligned and insulated
as before.

But the secret is to strain relieve that joint with the braid and the
external covering you apply over the joint. So, I roll the braids back
down, overlap them a bit, and then *solder* the braids at several spots
around the joint. I do this in such a way as to put a little tension on the
joint so that the braid will take any pull, not the center wires.

I have to seriously disagree with *not* soldering the braid. It takes only
a minute or less and ensures the shield continuity plus taking any stress
off the center wire.

A thorough wrap and seal as you describe and you have a joint that will
pass electrical and mechanical muster for HF applications with little
outward evidence that it is there.

Doing this for UHF and VHF cables is dicey, of course, but the worst that
can happen is a small impedance "bump" that may or may not be a problem.
Done properly, I agree with you that is is less disruptive that two end
connectors and a barrel connector.

You know, it was a lot more fun when we could dip the finals, and push in
the swinging link and watch that light bulb get brighter! Somehow, just
seeing the wattmeter needle move doesn't seem the same!   <:}

73/72/oo, George W5YR - the Yellow Rose of Texas         
Fairview, TX 30 mi NE of Dallas in Collin county EM13qe   
Amateur Radio W5YR, in the 56th year and it just keeps getting better!
QRP-L 1373 NETXQRP 6 SOC 262 COG 8 FPQRP 404 TEN-X 11771 I-LINK 11735
Icom IC-756PRO #02121  Kachina 505 DSP  #91900556  Icom IC-765 #02437


Merv Stump wrote:
> 
> > Gotta be a generation thing...
> >
> > I tuned my first rig for maximum brightness into a 40 watt light bulb and
> > then switched to the antenna;  I used a double pole double throw knife
> > switch to switch the antenna from transmit to receive; and every week I
> > saved 50 cents from my $5 allowance to buy another crystal which cost
> $2.95.
> > With my credentials established as a charter member of the "old fart's
> > club", I have to say I would not have believed that there was a ham
> anywhere
> > in the world who would not attempt to splice coax.  Have you tried it?  I
> > have, it works, and I will do it again. Here's how:
> >
> > First remove about a one inch piece of the dielectric and put it aside.
> As
> > carefully as possible role back the shield about 1 inch on each piece of
> the
> > coax.  Remove the dielectric for 3/4 inch on each piece.  Overlap the
> center
> > conductors by 1/2 inch and solder using as little solder as possible.
> Now,
> > take the piece of dielectric you put aside and split down one side; cut
> the
> > length to exactly fit the gap, and slip the dielectric over your spliced
> > center conductors.  Now as carefully as possible role the shields back
> down,
> > overlapping one with the other.  Do not attempt to solder the shields
> > together--just wrap tightly with good electrical tape extending the
> wrapping
> > about 1 inch over the ends of the cover on each piece.  Finally, cover the
> > whole thing with silicone sealant.
> >
> > I assure you this will have less loss and less impact on swr than 2
> pl259's
> > and a barrel connector.