Topband: Radial Plate Design

[Donald Chester]

> w8ji at w8ji.com
    
> Wed Feb  4 11:32:18 EST 2015

> I just twist my wires in a 
> "coherent lump", flux it with liquid flux, and flood the twisted area with 
> solder. If I get really sophisticated, I slide a piece of copper pipe over 
> the twisted area, crimp it, and flood the whole inside with solder.
>
> At towers, where people have to walk over the radials and a bunch of wires 
> are a PITA, I solder to a square made from copper flashing. 


NEVER use regular lead/tin solder if there is any possibility that it will come 
in direct contact with the soil. 
 
Minerals in the soil will quickly turn the solder to white powder. I once used leaded
solder to attach ground radials to a copper ring at the base of an inverted L. 
I ended up having to re-solder the entire ring of radials about once a month. 
The soldered connection would just fall apart, and the radial wires would fall loose from 
the ring.

The radials to my present vertical were attached using silver alloy brazing rods, heated
with a Mapp Gas torch. The rods and torch are widely available at plumbing suppliers, since 
it is against code to use regular lead solder with copper plumbing for the same reason that
it doesn't work with ground radials; minerals in the water eventually destroy the soldered 
connection and the pipe joint springs a leak, plus the danger that lead may leach 
and contaminate the drinking water. The rods are not cheap, but they are not prohibitively 
expensive either.

I brazed my radial system together in 1983, the soldered connections are buried below grade,
and the silver solder connections are as solid to-day as the day they were installed, with no
visible corrosion. Above-ground connections exposed to the elements over the past 32 years
likewise remain intact.

I use 15% silver content flat brazing rods, about 1/8" wide and 18" long. No flux is necessary. 
Copper sucks up that silver brazing alloy like a sponge soaks up water. 
Just remove any dirt or scaly corrosion with a wire brush; no need to polish the copper to
a sheen.

I could never understand why anyone would prefer to use a crappy metal plate with screw-on
connections, when it is so simple to silver-braze connections that will last for the life of the radial
system and vertical radiator, and will probably outlast the life of the antenna owner. A screw-on
connection, especially in contact with the soil and subject to outdoor temperature variations
will eventually fail. Those Hammy Hambone radial plates I have seen advertised are considerably
more expensive than a handful of silver brazing rods and a Mapp gas outfit.


Don k4kyv