[TowerTalk] FW: FW: Silver vs Aluminum vs Copper Re: OT: Inductor

[Matt]

Good point Jim,

I can back you up on the phosphor bronze as a dielectric as it does work
very well.   Regarding avoiding the SS hardware path, I have lately been
using AL or CU straps cut from a sheet placed right against the element. 

73
Matt
KM5VI

-----Original Message-----
From: TowerTalk [mailto:towertalk-bounces at contesting.com] On Behalf Of Jim
Thomson
Sent: Sunday, March 03, 2019 9:53 PM
To: towertalk at contesting.com
Subject: [TowerTalk] FW: Silver vs Aluminum vs Copper Re: OT: Inductor

Date: Sat, 2 Mar 2019 22:02:56 -0600
From: "Matt" <maflukey at gmail.com>
To: <towertalk at contesting.com>
Subject: [TowerTalk] FW: Silver vs Aluminum vs Copper Re: OT: Inductor
Calculator

<When the surface area of the anode is relatively large compared to the
<cathode, galvanic corrosion is generally not a problem when the stainless
is
<cathodic.   Hence using relatively small 18-8 stainless fasteners on
<aluminum elements or galvanized structures generally presents little
<interaction provided that the assembly is not in a salt laden or heavy
<chloride environment.   The British Stainless Steel Association has
<published some scholarly articles on this subject as well as NACE.

<I regularly use high chromium stainless washers to isolate copper from
<aluminum or zinc galvanize without issue.  A generous application of no-ox
<compound provides added protection and if using stainless threaded
<fasteners, anti-seize compound is a must.

<73
<Matt
<KM5VI

##  This is  the one thing that Mosely seems to have got correct, they used
Phosphor  bonze hardware  in several places. 

## F12  got it wrong where they used   SS  machine screws, with double nuts
to make   connections 
from wire leads from a CM balun to the feedpoint of the  DE on the   F12
yagis.   If they had put the lug
against the bare aluminum DE, then mashed it down with a SS flat washer and
SS  nut, all would be ok.
But  when the lug is placed between  2 x SS flat washers,   with a SS nut on
top, the  entire RF  current  
path   is via the  SS machine screw...and thats  bad news.   F12  tried at
one time using  8 gauge  solid  SS
wire as a hair pin on 40M.   Dead center in the SS hairpin, it  turned black
!    I had the same issue when
terminating cu strap  between  2 x SS  flat washers and  SS nut  on a vac
tune cap, doesnt work too good. 
Again, the high current  RF path flows through the SS machine screw.   Since
replaced with silver plated  brass hard ware.  

On one of the SW  broadcast supplier sites,  they used  phosphor bronze
hardware   on everything from 
1 kw  to  500 kw cxr.   Only the size of the  hardware changed.   Typ
ranging from  .25-20     up to 1.0 inch 
for phosphor bronze  bolts, and mating phosphor bronze washers, nuts etc.


Jim    VE7RF  

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