From: jimlux <jimlux@earthlink.net>
To: towertalk@contesting.com
Subject: [TowerTalk] Silver vs Aluminum vs Copper Re: OT: Inductor
Calculator
> <Complicating this is there's usually a nickel flash/strike plate under
> <the silver, to prevent silver/copper migration, and nickel is magnetic
> <and lossy.
>
<The paper that was linked by another list member comments that plating
<conductivity is often (much) lower than the plain metal, because of
<stuff added to make the plating actually work.
A .25 inch OD tubing coil will handle
> 41 % more current, due to skin effect, on 7 mhz... vs the same .25 inch OD
> tubing coil
> on 14 mhz. The same .25 inch OD tubing coil on 1.8 mhz will handle a
> whopping 2.82
> X more current... vs the same .25 inch OD tubing coil on 14.350
> mhz.....again due to
> skin effect. It goes to the sq rt of the ratio of the freqs.
I don't know about "handle more current" - the RF resistance goes up as
the square root of frequency, so the dissipation goes up as sqrt(f) too.
..............................................................................................................................................
### There is no nickel flash used in the formulation, per the msds sheet for
the cool amp
product, used to silver plate cu etc. Power companies use it to silver
plate the ends of cu buss bars,
where they over lap..and thats at 60 hz. It also works good when Dc is
applied to cu buss bars...where
they overlap.
I have managed to solve a lot of int issues, esp RX, when the cool amp glop
is applied to existing contacts
on relays etc. I had brand new 30A deltrol and also P + B relays with int
high dc resistance between NC and COM
contacts..and also between NO and COM contacts. Once the cool amp glop
applied correctly, dc resistance
dropped to zero. Problems solved.
## Re-read my post above. As freq increases, RF current handling
decreases.... assuming
the same cu tubing OD is used. .25 OD Cu tubing will handle 41% more RF
current on 7 mhz..
vs 14 mhz. With SAME RF current applied, the .25 OD cu tubing will run
hotter on 14 mhz, vs 7 mhz.
This is why stuff like tank coils in linear amps start off with smaller gauge
wire on 160m... and progressively
increase in gauge, as freq increases. On 10m band, coils need to be
quadruple the diameter vs 160m.
Easier said than done however. Saving grace is... typ uh values on 10m band
are really low. This is where
strap coils work good, and are easily made..which also works good on 12m , and
also 6m. I also used strap
coils on my 40m yagi boxes, since the required uh was very small. Wound
from 1 inch wide cu strap, and 1.5 inches
ID..and aprx .036 inch thick cu strap. 2 x vac relays used per coil, tapped
at 1/3 and also remaining 2/3.
4 x segments result. In the nema boxes I used, I had plenty of length, but
not a lot of height and width to play with,
so using tubing coils was out of the question for that particular application.
## aluminum tubing works great for yagi eles, but when using aluminum wire,
or alumoweld wire for wire ant applications,
is difficult to work with, and make solid connections to.
Jim VE7RF
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