Anodized Alumium for Antenna Elements
 

Hi folks, I'm in the process of building myself a screwdriver antenna
for my truck. Being the vain sort, I'd like it to end up being black
as that matches nicely with the other bitties sticking out of the
vehicle.

Q.- Does anodyzing negatively impact aluminum's ability to efficiently
radiate? I seem to recall reading somewheres that anodyzing leaves a
non-conductive surface, but on the other hand aluminum oxide ain't
supposed to be that great a conductor either & that whats on the
surface of any piece of aluminum thats seen air for more than a few
minutes.

Enquiring Minds want To Know-

Howard.

The radiating surface don't care. Just make sure all mechanical contacts which need to conduct penetrate the anodizing.
Like where the coax connects, or where the coil is connected.

--
Crazy George
The attglobal.net address is a SPAM trap. Please change that part to: attdotbiz properly formatted.
"Howard Eisenhauer" wrote in message
...
Hi folks, I'm in the process of building myself a screwdriver antenna
for my truck. Being the vain sort, I'd like it to end up being black
as that matches nicely with the other bitties sticking out of the
vehicle.

Q.- Does anodyzing negatively impact aluminum's ability to efficiently
radiate? I seem to recall reading somewheres that anodyzing leaves a
non-conductive surface, but on the other hand aluminum oxide ain't
supposed to be that great a conductor either & that whats on the
surface of any piece of aluminum thats seen air for more than a few
minutes.

Enquiring Minds want To Know-

Howard.

Hello Sir George and Howard:

Anodizing the aluminum is kind of over kill as I have measured new
antennas and old antennas with 30 plus years of exposure to the
elements. No difference measured.

What did throw me a curve was buying Anodized Surplus Aluminum Tubing in
Burbank Ca, and making a vertical for the VHF Low Band. Ok no problem
getting it together and should have tuned in a few minutes.

But no it was responding to a much higher frequency than the 31 Mc I
wanted it to tune to. After checking and double checking everything and
replacing the coax and antenna analyzer it still measured a way high
frequency SWR null.

Now faced with the strong reality that this thing was gonna kick my a$$,
after a hole day of going nutzoid. I got my old Simspon 260 VOM and
measured continuity from all the elements. I found that one of the
vertical elements had been anodized on the inside causing a no
connection condition.

Cutting off a metal wire brush and putting the shank in Mr. 1/2 inch
chuck, drill motor, and the 100 foot cord (I have given up on battery
operated drill motors) the inside of the tubing was now nice and shinny
bright aluminum.

The antenna tuned up as designed. So keep your eyes open when using
anodized aluminum tubing. And I think this is why some antenna
manufactures do not anodize their aluminum tubing. Plus the added
manufacturing costs.

Jay in the Mojave

Crazy George wrote:

The radiating surface don't care. Just make sure all mechanical contacts which need to conduct penetrate the anodizing.
Like where the coax connects, or where the coil is connected.

--
Crazy George
The attglobal.net address is a SPAM trap. Please change that part to: attdotbiz properly formatted.
"Howard Eisenhauer" wrote in message
...

Hi folks, I'm in the process of building myself a screwdriver antenna
for my truck. Being the vain sort, I'd like it to end up being black
as that matches nicely with the other bitties sticking out of the
vehicle.

Q.- Does anodyzing negatively impact aluminum's ability to efficiently
radiate? I seem to recall reading somewheres that anodyzing leaves a
non-conductive surface, but on the other hand aluminum oxide ain't
supposed to be that great a conductor either & that whats on the
surface of any piece of aluminum thats seen air for more than a few
minutes.

Enquiring Minds want To Know-

Howard.

On Sat, 09 Apr 2005 15:38:23 -0700, Jay in the Mojave
wrote:

Anodizing the aluminum is kind of over kill as I have measured new
antennas and old antennas with 30 plus years of exposure to the
elements. No difference measured.

That might be ture in the Mojave but come up here on the norhern
California coast - on the ocean - and you 30+ aluminum antenna will be
noting more that a memory.

Danny, K6MHE

Jay in the Mojave wrote:
... a much higher frequency
than the 31 Mc ...
^^
Showing our age, are we Jay? :-)
--
73, Cecil http://www.qsl.net/w5dxp

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Jay in the Mojave wrote:

Hello Sir George and Howard:

Anodizing the aluminum is kind of over kill as I have measured new
antennas and old antennas with 30 plus years of exposure to the
elements. No difference measured.

Interesting, as I have measured antennas with only 2 years exposure that
had .5 dB measured difference. A 432 MHz antenna scrubbed with a
ScotchBrite showed a .6 dB gain increase.

So B as in B, S as in S, as we say here in Minnesota.

tom
K0TAR

On Sat, 09 Apr 2005 21:12:47 -0500, Tom Ring
wrote:
A 432 MHz antenna scrubbed with a
ScotchBrite showed a .6 dB gain increase.
So B as in B, S as in S, as we say here in Minnesota.

Hi Tom,

You could measure to the accuracy of better than 0.2dB between two
separate tests? And at UHF too? Care to share how?

73's
Richard Clark, KB7QHC

Hello Cecil:

Ok well thats two of us then, .... hehhehe

Jay in the Mojave

Cecil Moore wrote:
Jay in the Mojave wrote:

... a much higher frequency

than the 31 Mc ...
^^
Showing our age, are we Jay? :-)

Hello Dan:

So what do you use for being near the ocean?

Do you have to anodize all the aluminum tubing to keep the antennas up?

Jay in the Mojave


Dan Richardson wrote:

On Sat, 09 Apr 2005 15:38:23 -0700, Jay in the Mojave
wrote:


Anodizing the aluminum is kind of over kill as I have measured new
antennas and old antennas with 30 plus years of exposure to the
elements. No difference measured.


That might be ture in the Mojave but come up here on the norhern
California coast - on the ocean - and you 30+ aluminum antenna will be
noting more that a memory.

Danny, K6MHE

Jay,

We just replace them more frequently than dry desert dwellers. After
about five years (sometime sooner) they are about shot.

My two-meter omni is incased in a fiberglass radome and my wire
antennas are made with insulated wire with ends sealed.

Danny, K6MHE



On Sun, 10 Apr 2005 02:08:57 -0700, Jay in the Mojave
wrote:

Hello Dan:

So what do you use for being near the ocean?

Do you have to anodize all the aluminum tubing to keep the antennas up?

Jay in the Mojave


Dan Richardson wrote:

On Sat, 09 Apr 2005 15:38:23 -0700, Jay in the Mojave
wrote:


Anodizing the aluminum is kind of over kill as I have measured new
antennas and old antennas with 30 plus years of exposure to the
elements. No difference measured.


That might be ture in the Mojave but come up here on the norhern
California coast - on the ocean - and you 30+ aluminum antenna will be
noting more that a memory.

Danny, K6MHE