[TowerTalk] Loading Coils

[W7TMT - Patrick]

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 at contesting.com> On Behalf Of Richard (Rick) Karlquist
Sent: Sunday, August 3, 2025 07:50
To: towertalk at 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
>>
> 
> _______________________________________________
> 
> 
> 
> _______________________________________________
> TowerTalk mailing list
> TowerTalk at contesting.com
> http://lists.contesting.com/mailman/listinfo/towertalk
> 


_______________________________________________



_______________________________________________
TowerTalk mailing list
TowerTalk at contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk