Topband: Conductivity of stainless steel hardware

[Charlie Cunningham]

Amen!

Charlie, K4OTV

-----Original Message-----
From: Topband [mailto:topband-bounces at contesting.com] On Behalf Of Tom W8JI
Sent: Sunday, January 26, 2014 11:26 AM
To: Charles Stackhouse; topband at contesting.com
Subject: Re: Topband: Conductivity of stainless steel hardware

Some of the longest most drawn-out debates (and fights) come from dealing 
with how much is good, how much is OK, or how much is bad. It goes on and on

with everything until our heads spin.

<<<
A very tech savvy friend (microwaves, public safety radio) says this is no 
good. Due to the poor
conductivity of stainless steel, RF connections should not be through the 
hardware but through wires brought out of the boxes soldered directly to the

antenna wires.

I would appreciated the advice of this group.>>>>>

It sounds like your friend is single-focused only on the material type, and 
ignoring other issues that are as important or more important. I've seen 
this happen countless times in tank circuits and other places dealing with 
materials, even relying on "goofy" microwave oven tests.

In this case, resistance or loss is a combination of:

1.) The impedance of the system at that point, the lower the impedance the 
higher the loss...all other things equal

2.) The depth and number of any threads, or other surface characteristics. 
The more irregular and deeper the valleys and peaks, the higher the 
loss....all other things equal

3.) The cross-sectional area carrying current. The smaller the current 
carrying cross section, the greater the loss....all other things equal

4.) The frequency

5.) The exact material

6.) What is around that material that might affect current distribution

The loss can range from immeasurable, which is probably virtually all cases 
at HF and lower VHF, to significant in certain situations.

I would say, in your application, if the scale is like this:


immeasurable...........unnoticeable.............noticeable...........worriso
me...............significant

you are probably between the "m" or "r"  on "immeasurable" side of the line.

:-)

To measure the loss, the measurement would have to be caloric. You could run

a dozen amperes and measure temperature rise of a long thermally isolated 
sample of the screws. Then you could estimate effective resistance per 
linear inch.

I certainly would not lose any sleep over what you are doing.

73 Tom 

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