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Re: [TowerTalk] Loading Coils

To: towertalk@contesting.com
Subject: Re: [TowerTalk] Loading Coils
From: David Gilbert <ab7echo@gmail.com>
Date: Sat, 2 Aug 2025 16:06:18 -0700
List-post: <mailto:towertalk@contesting.com>

Yeah, amplifier coils are a different animal than antenna loading coils.  Lots different circuit impedance and lots different current levels.

Still, his point is valid if you use a tank coil for a comparison. Nickel is simply a really bad idea for plating a loading coil unless it is so thin that it is hardly there.  If the nickle plating thickness is significantly less than the skin depth (which is 0.65 microns at 30 MHz) then it essentially isn't there for RF.  We're not really talking plating then ... we're talking what I used to see referred to as "flash".

And yes, nickle is harder to solder to.

Dave   AB7E



On 8/2/2025 1:37 PM, john@kk9a.com wrote:
As far as aluminum coils go, they may not be good for amplifiers but several
big name antenna companies use them on 40m Yagi elements for loading and
they appear to work well.

John KK9A


Jim VE7RF wrote:


##  nickel plated,  He's joking right ?  Years ago, I replaced the silver
plated copper tubing coil in a hb amp with an IDENTICAL  aluminum tubing
tank coil.  Talk about HOT.

Nickel ?    You may as well douse it with lighter fluid, and toss in the
zippo.
Measure the Q of the nickel plated coil vs the copper coil, or silver
plated copper coil......and you will be in for a rude awakening.

Nickel is worse than phosphor bronze.  I just ran a typ 160m  coil through
K6STI's ' coil'  software....and using copper the Q was 1222.   With
phosphor bronze, it dropped to 464.....and nickel plated is even worse !  (
aluminum was a  Q of 857  using 3003-0 alloy).

No doubt he wanted nickel so it was weather resistant.

I wind my own copper tubing coils....then silver plate em.

Jim  VE7RF


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