Virtually any metal can be silver plated, even aluminum. Depending on the
material, there may be one or more layers of other material applied before
the silver. Aluminum for example requires a layer of nickel then copper and
finally silver. A local plating company can discuss all this with you.
I have had stainless steel screws silver plated for use inside a 1296MHz
plate cavity. The cost was reasonable as I recall. There is a potential
problem of mixing up screws when disassembling for repairs. No danger of this
when copper screws are used as the appearance is distinctively different.
73,
Gerald K5GW
The big bolts used in telco copper buss bars years ago were solid copper;
not sure about these days.
In a message dated 11/23/2010 12:36:56 A.M. Central Standard Time,
fqm@msn.com writes:
--Forwarded Message Attachment--
From: jim.thom@telus.net
To: amps@contesting.com
Date: Mon, 22 Nov 2010 05:23:14 -0800
Subject: [Amps] brass or BNP hardware
Date: Fri, 19 Nov 2010 13:36:22 -0700
From: "John Lyles" <jtml@losalamos.com>
Subject: [Amps] brass or BNP hardware
In RF power amplifiers, HF to VHF range, I have used brass or nonmagnetic
stainless steel hardware for years, after having been "Burned" by steel
screws - pun intended. Several times in my career
I have seen bolts turned black and tarnished from RF heating this way. If
RF current can flow in the steel, then it can make eddy currrent losses and
heat up. However, if it is not carrying current, not a problem.
The reason I try to stick with brass or SS is that later on, someone is
working on the product, cannot remember why this special screw is only in
this hole and that. So by making it all one type, when inside the RF
compartment, you
make service, repair and spare parts inventory simpler. These simple
policies are carried on in my mind when starting new amplifiers.
73
John
K5PRO
## In Bings infamous RF software, one of the features is the skin depth
calculator. It also has a table that list every kind of metal you can
think of. The worst of the bunch was SS. Per his
list, rusted bailing wire would be better than SS. He didn't say whether
it was magnetic, or non magnetic SS.... or if 304 SS or the cheaper
variety..which I think is 18 type.
SS appears to work fine, if used to clamp cu straps together, etc, where
the main RF current patch is not though the actual SS threads. IE: cu strap
wrapped around a tubing tank coil, brought back on itself, then
machine screwed, which pinchs the cu strap tightly, onto the tank coil.
Where I got into trbl was when double nutting SS machine screws and
placing strap between the two nuts. Then the RF path is now through the
SS threads
and stuff heats up..fast. [ I did this on a ceramic vac cap]
The SS that's locally available in common sizes like 4-40, 6-32, 8-32,
10-32 1/4-20 etc... will just barely stick to a magnet...and I mean
barely...and that's with a big magnet. If a small magnet is used, they won't
stick at all.
N6BT once had a pix on his old F-12 website, where he tried using solid 8
ga SSS wire for a 40m helical hair pin. The exact dead center of the
coil had turned jet black..over a +/- 1 " portion.
F-12 typ uses SS 10-24 hardware at feed point of their ants/yagis'.
They also double nut them... with the balun lugs between the 2 x nuts.
## I noticed on one of these sites that supplies ant materials for high
power AM SW broadcast and commercial users.... recommended sizes of
hardware for the feed points of various SW ants...
including curtain array's... rhombics, V beams, LP yagi's etc. It went
from 1/4-20 and 1/4-28 up to real big stuff like 3/4"..and 1". It
was a table of power VS bolt size. Interesting enough... ALL the bolts
used consisted of phosphor bronze. None of it was SS / brass / or
nickel plated brass.....or anything else. I'm sure Mosley used phosphor
bronze screws for the feed-points of their yagis.
## so what's the story on Phosphor bronze? Is it really the preferred
material to use for RF ?? I have yet to try to see if I can silver
plate any of this stuff. Back in the 70's/ 80's and early 90's.. telco's
used copper bolts into tapped copper buss bars on a regular basis.
[1/4"-20 + 5/16"] But I don't think they were solid copper. I think they
were copper plated material, but don't know what the base material
was. I didn't want to scrape any cu off... exposing the base metal, if
they were plated... as the CU bolts were scarce to start with, and we
needed all of em.
## Brass is plentiful at the local stores. I was surprised that they
even stocked huge 5/8" hex headed brass bolts, in various lengths. I
have never seen nickel plated brass... and never heard of it
till now. Phosphor bronze on the other hand, is readily available
from a variety of sources, in just abt any size. I have never had any
problems with silver plating CU. Dunno if it's even possible to silver
plate say
phosphor bronze, SS, or brass/nickel plated brass. I don't like the
way SS interacts with Aluminum tubing or Aluminum plate. The AL
always ends up grossly discoloured.
later....... Jim VE7RF
+++ Silver plated stainless steel screws and bolts do exist. We use them
in
high-vacuum systems, the silver plating acting as a thread lubricant.
Most vacuum systems are stainless chambers, tubing and flanges, with
stainless
hardware used as fasteners. The screws tend to be a little expensive,
probably because of the limited market for them. In a pinch I have our
plating shop silver plate ordinary 304 stainless screws. It works.
Mike K6MDS
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|