Regarding the need for any type of plating over copper, Greg, W8WWV had written
extensively about building high Q coils and has also done an analysis of the
coil characteristics after one has been in outdoor service for years.
His build article is here:
http://seed-solutions.com/gregordy/Amateur%20Radio/Experimentation/HiQCoil.htm
His follow up, including the testing he did of a coil with long outdoor
exposure and its electrical characteristics before and after cleaning can be
found here:
http://seed-solutions.com/gregordy/Amateur%20Radio/Experimentation/HiQCoil2.htm
73
Patrick, W7TMT
-----Original Message-----
From: TowerTalk <towertalk-bounces@contesting.com> On Behalf Of Richard (Rick)
Karlquist
Sent: Sunday, August 3, 2025 07:50
To: towertalk@contesting.com
Subject: Re: [TowerTalk] Loading Coils
WOW! Many thanks to Wes for finding this obscure, but extremely valuable paper
and posting it to TT. Whenever Wes posts here, I make sure to read the post.
This paper completely debunks huge amounts of folklore. It confirms various
suspicions I have always had, such as the fact that the magnetic parameters of
nickel at RF are unpredictable so it is safe to assume they are very bad, and
that nickel should never be used for RF coils. I have been a consultant to a
lot of companies doing high power RF and I am always on the look out for nickel
plating. The clients will tell me how great nickel is for various reasons.
But I have to tell gently tell them it is a non starter for RF. No the
customer is not always right.
The company I currently work for has air core inductors custom made using
ordinary tinned copper bus wire. I have measured the inductance of these coils
and it compares very favorably with the predicted Q of our coils if bare copper
wire were used. (See Medhurst's 1947 paper on the subject). Tin does have
considerably lower conductivity vs copper, but at least it is non-magnetic.
Also, the thickness of the tin plating is so thin that it is negligible in
terms of skin depth. Even when it is old wire that is no longer shiny bright,
it still doesn't ding the Q.
At least for indoor work, tinned copper for my money is the way to go.
73
Rick N6RK
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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