[TowerTalk] Loading Coils

[Michael Tope]

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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