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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