Re: [A/S] Refurbishing old TV antenna

[Rick Kunath <k9ao@xxxxxxxxxxx>]

> 
> I was on the roof doing some other work yesterday and decided to
> clean the oxidation and dirt off the tines with some steel wool.
> They were really dirty.
>

Oxidation on the aluminum antenna elements is conductive, so don't worry about 
getting them clean. It won't help the reception. 

Make sure any contacts are clean though.

>
> I'd really like to splice in some new outdoor rated twin lead antenna
> wire on the roof, but have heard that a splice will weaken the
> signal.  

Go with the splice.

It won't weaken the signal if done correctly. 

Here's what to watch out for:

Theh 300 ohm impedance of the twin-lead antenna cable is determined by the 
spacing between the wires (and the wire size, but you won't be altering that) 
and the dielectric (insulating) material between the wires. 

To make a good splice and maintain the proper presence of the dielectric 
between the wires to prevent an impedance bump and reflections (which can 
sometimes cause a ghost in the picture), make a scarf joint. In other words 
cut one wire back a couple on inches shorter than the other (just the wire 
and not the dielectric between the two wires) and do the opposite with the 
new cable. Make sure that your new cable is not a clear or nylon-type color, 
as it will break down from sunlight. The outdoor stuff is brown. 

Fit the new cable together with the old cable and solder the connections. Use 
some shrink tubing over the entire splice to seal it and reinforce it. 

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Excuse the crude ascii art, but you get the idea. What the crude art fails to 
show is that the dielectric of each piece overlaps between the splices. In 
other words, there is a double layer of dielectric. This deals with 
maintaining the impedance as well as reinforcing the splice.

IF this does not show correctly use a fixed font.

Then connect the new cable end to the antenna and seal the connections against 
the weather. 

Rick Kunath
WBCCI #3060