[TowerTalk] Loading Coils

[David Gilbert]

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 at 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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