[Antennas] Stainless Steel Conduits

Fri Mar 13 22:06:04 EDT 2015

On 03/13/2015 07:11 PM, Richard (Rick) Karlquist wrote:
> On 3/12/2015 6:33 PM, charles berry via Antennas wrote:

>> Is Steel Conduit suitable for J-Poles and Active Booms? The price of
>> copper has made it extremely problematic in building antennas. How is
>> steel's velocity factor different than copper?
>> Thanks,Chuck BerryN7CHS

> Now if you did try to use a stainless steel tube for
> RF purposes, that is a problem. Not only is the DC
> resistance much higher than aluminum, but some SS is
> magnetic, which makes it even lossier at RF.
> I had a client once who wanted to use some nickel
> tubes to make a transmission line. (I know, dumb
> idea, but the client (who has money) is always right.)
> I measured the RF resistance of the nickel and found
> that it was much higher than would be predicted by
> DC resistance. This indicated that the magnetic
> permeability was a big factor. Stainless steel has
> both nickel and chromium in it.

> You do see stainless steel CB whips (102 inch) which
> have to be made of SS for mechanical reasons. You
> just have to live with the extra RF loss. Mobile
> installations have many other sources of loss, so
> in the overall scheme of things, the SS whip is not
> so bad. But it is a special case. I love my 4 inch
> Hi-Q screwdriver with a 102 inch whip on top.

> Finally, velocity factor is a property of dielectrics
> not conductors. A stainless steel CB whip resonates
> at 27 MHz, just like it would if it were made of copper.

 Copper, aluminum, brass and stainless steel are used to
make major brands of FM broadcast transmitting antennas.
Aluminum, and galvanized steel are used to make major
brands of TV broadcast transmitting antennas.
None have a reputation for being more or less efficient than
the other. The only known differences are the differences in
strength, weight and the costs.
 (there are known efficiency differences between antenna designs)
 I think the difference in the antenna efficiency between
copper wire and stainless steel wire is being exaggerated in
these web-sites and discussions.
 I am sure the difference between a sturdy "J pole" antenna made
with copper (silver soldered) and stainless steel (brazed) of
the same size and design will be so similar in efficiency, cost
and longevity that they would be virtually indistinguishable.
Copper is much easier to machine and join than stainless steel.
-- 
 Ron KA4INM - Youvan's corollary:
 Every action results in unwanted side effects.