Topband: Soldering radials?

[K9AY]

Rick,

I used to work on AM broadcast systems -- used both Stay Brite 3% with a propane torch, and 15% silver-bearing brazing rod with a small welding torch. As far as I could tell, both worked well electrically. The brazed joints were stronger, mechanically.

My own system (installed 2008) had its 120 radials soldered using home center supplies for copper plumbing, mostly Oatey Safe-Flo (Sn-Ag-Cu-Bi, 420-460ºF). Exact percentages are not published, but the hazardous materials declaration says "1-5%" for each alloying metal. Just guessing, it may be 95% Sn, 3% Au, and 1% ea. Cu and Bi. Radials are still solidly attached to the copper strap at the tower base. No sign of deterioration, just brown oxidation.

I used both Oatey paste flux and bottled HCl acid flux (Stay Brite). The HCl seems to work better unless there is heavy oxidation on the copper. But you'll need to sand or wire brush it anyway. No corrosion problem with acid flux. Mine haven't even turned green much; probably gets washed off with rain.

In the past I've looped clean bare wire around stainless bolts, under fender washers, but none of those were in place more than 2-3 years so can't judge long-term performance.

73, Gary 
K9AY




Date: Wed, 12 Oct 2016 08:52:40 -0700
From: "Richard (Rick) Karlquist" <richard at karlquist.com>
To: "Topband at contesting.com" <Topband at contesting.com>
Subject: Topband: Soldering radials?
Message-ID: <c04783d1-8f96-c17c-5921-fb6648e8587e at karlquist.com>
Content-Type: text/plain; charset=utf-8; format=flowed

I'd like to get the latest thinking from the group
on soldering radials.  What I currently thinking
is as follows:

SOLDER SELECTION:

1.  Tin lead doesn't hold up in the weather.

2.  "Stay Brite" 3% silver solder (97% tin,
no lead) is known to work well, but is expensive,
and has a considerably higher melting point
than 63/37.

3.  Lead free plumber's solder obviously works
in water pipes, but does it hold up outdoors
in the rain?  What is the melting point?

FLUX SELECTION:

1.  Pure rosin.  Hardest to work with, but minimum
corrosion issues.

2.  Activated rosin.  Easier to work with.  What
corrosion issues are there?

3.  Acid core plumber's flux.  Very easy to work
with, very corrosive.  Does this hold up in the
rain, etc?

(I remember the dire warnings that Heathkit manuals
had about not using acid core solder, but I
guess that doesn't apply to radials.)

CRIMPING?

Has anyone tried crimping as an alternative to solder?

Rick
N6RK