[TowerTalk] Solid 160 radial plates?

Jim jimw7ry at gmail.com
Wed Aug 29 07:34:00 EDT 2018

Actually, silver bearing solder (15%) is called by the trade name of Silfos
(which is probably a brand of silver solder).

It's not used by the plumbing industry per se.. It's used in the HVAC trade
for refrigeration/air conditioning tubing welding.

That's why you see the fittings in HVAC are black, because they have been
heated to red hot and braised with Silfos.

There are lower values of silver bearing solder out there, but 15% is best
and a bit expensive.

Jim W7RY

-----Original Message-----
From: TowerTalk [mailto:towertalk-bounces at contesting.com] On Behalf Of
Donald Chester
Sent: Tuesday, August 28, 2018 12:39 PM
To: towertalk at contesting.com
Subject: Re: [TowerTalk] Solid 160 radial plates?

> I'm not sure what the metallurgy of the screw and bar would be like in 
> conjunction with solder.  Of course the bar should be fine with copper 
> (and I think even with aluminum in alkaline soil environments), so if 
> I was hesitant about screwing down on multiple small wires (a valid 
> concern, I think) I'd probably solder the smaller wires to one larger 
> one to go into the bar.  And of course I'd use lead free solder since 
> lead and moisture are bad bedfellows.

> I probably wouldn't bury the bar underground because you never know 
> what corrosive effects might be there, but you can screw the 
> connections so tight that I'm pretty sure the metal to metal interface 
> approaches that of a weld.  I don't think having it exposed to the 
> elements above ground would be a problem.

I don't understand why you guys waste time, energy and money with those
Hammy Hambone radial plates in which the radials are attached with screws.
Much easier, cheaper and longer lasting is to lay a copper ring round the
base of the tower, and solder/braze the radials to it.  The ring can be made
of copper tubing, solid #4 awg wire, or strips of sheet copper. This has
long been the standard procedure for AM broadcast towers.

Braze the radials to the ring using the same silver solder plumbers use.  It
comes in sticks about  18" long and 1/8" wide; the alloy is  15%  silver,
lead free.  You need something hotter than an ordinary propane  torch; I use
MAPP gas, which works just like a propane torch.  It must heat the copper to
a dark red glow to fully melt the alloy to liquid form. As long as the
copper is free of scaly crud, no external flux is needed; the heat burns
oxides off the bright copper.  The molten solder adheres to hot copper like
a sponge soaks water. The connection does not deteriorate over time in
contact with in the soil.  I built mine in 1983, and the connections to-day
are just as solid as the day I put them in, with no signs of corrosion.  The
same with above ground outdoor feedline and antenna connections.

The silver alloy brazing rods are available at any plumbing  supplier.  They
are not dirt cheap, but not overly expensive either, since plumbers use them
for sweating copper pipes.  Codes prohibit lead solder for plumbing, so
demand is high and supply plentiful.  NEVER use ordinary lead solder; it
reacts with minerals in the  soil and quickly deteriorates and turns into a
white powder.  I once used lead solder years ago for a radial system and had
to routinely re-solder the radials about once a month.  That's why lead
solder is not used in plumbing; minerals in the water cause the same
deterioration of the solder and the connection will eventually leak.  Plus,
there is concern about lead leaching into the potable water supply.

The only circumstances where "radial plates" MIGHT be a useful solution
would be for temporary installations, like a field day setup or experimental
antenna.  I would never use them for a permanent installation.


Don k4kyv


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