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RE: RE: sewer pipe Meisse Reply



Interesting discussion. Here is my experience: I built an antenna rig for
AO-40 consisting of a 2 foot dish with two helix antennas as feeds, one for
2Ghz mounted within one for 1Ghz. Both were made of thin wall plastic tubes
with 3M 1/4" wide tape wound thereon. They were very poor performers. I
disassembled and soldered onto the 3M tape #12 copper wire and re assembled.
They worked wonderfully! My conclusion was that the problem was that the
tape offered only a couple mils of thickness perpendicular to the actual
wave front while the #12 wire occupying exactly the same location increased
that by a quantum factor resulting in success. Remember the discussions of
years ago regarding the size of the radiator influencing the result.
Additionally, in my day job, I noticed the same sort of thing with
commercial FM transmitting antennas. The antennas made of 3" copper pipe
perform much better than those with 3/4" radiators. Of real interest is that
the bandwidth of the large conductors is far better.
Regards,
Gunther Meisse
W8GSM
AMSAT LM:594


-----Original Message-----
From: owner-AMSAT-BB@amsat.org [mailto:owner-AMSAT-BB@amsat.org] On Behalf
Of George Henry
Sent: Monday, May 01, 2006 8:45 AM
To: amsat-bb@amsat.org
Subject: Re: [amsat-bb] RE: sewer pipe

I wouldn't rule out the copper tape as the culprit, Art... I also tried to
make a couple of 2.4 GHz helix antennas with copper tape on PVC pipe, also
with poor results.  However, a helix wound on the same pipe with #12 solid
copper wire performed as expected.  I blamed the tape....

George, KA3HSW

-----Original Message-----
>From: kc6uqh <kc6uqh@cox.net>
>Sent: May 1, 2006 12:31 AM
>To: K3IO@verizon.net, AMSAT BB <amsat-bb@amsat.org>
>Subject: Re: [amsat-bb] RE: sewer pipe
>
>As a suggestion do not over look the dilectric constant and the 
>thickness of the pipe. At 2 GHz the thicker pipe can cause refraction 
>of the wave. This is not related to the disipation factor that is 
>tested in the microwave oven. If used as a raydome best to make it a 
>larger diameter and choose a thin wall pipe to  reduce this effect. 
>Test in the far field will show if there is a problem by testing with the
raydome on and off.
>I tried several helix at 2.4 GHz made with copper tape wound on acrilic 
>tubing with poor results. I suspect that this was in part the reason.
>
>Art,
>KC6UQH
----
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