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Re: [TowerTalk] Loading Coils

To: towertalk@contesting.com
Subject: Re: [TowerTalk] Loading Coils
From: Michael Tope <W4EF@dellroy.com>
Date: Sun, 3 Aug 2025 08:55:40 -0700
List-post: <mailto:towertalk@contesting.com>
Yeah, Dave, it seems improved RF resistance brought about by the high phosphor content comes at a cost. I found this white paper that compares nickel-phosphorus to other plating methods in the context of RF connectors:
https://www.rosenberger.com/fileadmin/content/headquarter/News/2020/Paper_Salt_Spray_28.07.2020.pdf

In addition to poor solder-ability, nickel-phosphorus doesn't score well for contact resistance (this could be relevant to the tapped inductor configuration with the little copper alligator clips). It is also somewhat brittle. For soldering, I suppose you could sand off the nickel, but that seems like a PITA.

Now, I am really curious what sort of nickel plating they are using on those inductors :-)

73, Mike W4EF...............

On 8/3/2025 12:08 AM, David Gilbert wrote:

ChatGPT mostly agrees with you, except that it says that nickel with a high phosphorus content is almost impossible to solder to even when using an aggressive acid flux.

Dave   AB7E


On 8/2/2025 7:54 PM, Michael Tope wrote:
Wes,

I remember looking into this for a work project. If the phosphorus content in the nickel plating is high enough, the relative permeability drops to a low value close to 1 (i.e. the nickel alloy becomes non-magnetic). If you look at page 156 paragraph (6) Nickel-Phosphorus, a higher phosphorus content decreases the conductivity of the alloy. In that case, copper plated with a modestly thin layer of low-conductivity nickel-phosphorus alloy (say 200 micro-inches) should have an overall AC resistance at HF frequencies that is fairly close to un-plated copper (see figures 5, 6, and 7).

It would be interesting to get hold of a few of these inductors to see how well they perform.

73, Mike W4EF...............

On 8/2/2025 10:15 AM, Wes wrote:
Actually, I know it's a bad idea, see top of page 151 of the following.

https://www.dropbox.com/scl/fi/w5u2m0qvuwjs0i3vlwdsf/Plating.pdf?rlkey=n99dlrd2joh5548drtczvtsks&st=grysczj9&dl=0

On 8/1/2025 2:29 PM, Wes wrote:
I would need some convincing that nickle plating is a good idea.

Wes  N7WS


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