[Antennas] Stainless Steel Conduits

[Richard (Rick) Karlquist]

At last a legitimate reason for using copper,
because it is an implementation convenience,
as opposed to the marketing hype on the web
page that was cited.

Rick N6RK

On 3/14/2015 7:04 AM, Jim Hargrave wrote:
> I have built J-Pole antennas for many years. I prefer the copper
> mainly because it is easy to build especially for VHF/UHF.
>   It also solders readily, making it easy to tune  the feedline to
> the stub.
>
> I have a tri-band J-Pole (146/223/440) on top of my tower that I
> built in the early 1980's and it has never required any maintenance.
> It is built using 1 in, 3/4 & 1/2 in. copper water pipe. Couplings,
> elbows, caps & Reducers are readily available at most hardware and
> plumbing supplies.
>
> 73, Jim - w5ifp at gvtc.com
>
>>> -----Original Message-----
>>> From: Antennas [mailto:antennas-bounces at mailman.qth.net] On
>>> Behalf Of KA4INM
>>> Sent: Friday, March 13, 2015 9:06 PM
>>> To: a
>>> Subject: Re: [Antennas] Stainless Steel Conduits
>>>
>>> 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.
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