Hi Paul, simple answer on Your question is: 2 feeders; multi-band Mox in square
shape only; 1 to 1 balun is recomended, and contact me on muzikant@sezampro.yu
for picture and construction details. I prefere my 3L/3b Moxon 20/15/10m,
73 to all Andra YU1QT
----- Original Message -----
From: antennaware-request@contesting.com
To: antennaware@contesting.com
Sent: Monday, April 21, 2008 6:00 PM
Subject: Antennaware Digest, Vol 54, Issue 7
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Today's Topics:
1. 20m Moxon beam (Paul Young)
2. Re: building a TAK-Tenna ??? (Terry Conboy)
3. OT XM240 Loading Coils (Gedas)
4. Grounding needs (Howard W3CQH)
5. Re: Grounding needs (K9AY)
----------------------------------------------------------------------
Message: 1
Date: Sun, 20 Apr 2008 18:18:42 +0100
From: "Paul Young" <paul@g0hwc.com>
Subject: [Antennaware] 20m Moxon beam
To: <AntennaWare@Contesting.com>
Message-ID: <83356CB27EF5414996385AB3100A58DE@PaulPC>
Content-Type: text/plain; charset="iso-8859-1"
Hi all,
I am going to be building a Moxon beam for 20m.
I have got 4 fiberglass poles for the spreaders and trying to find the best
way to fix them to the 2 inch mast.
I have looked on the moxon project website but would like to see other ways
of mounting.
http://www.moxonantennaproject.com/
Also would like to hear what others think about fitting a 1 to 1 balun or not
?
And how will it affect things if I add a 15m loop within the 20m loop?
Would I be best to have 2 feeders or the one ?
Many thanks for your time
Paul G0HWC
Check out my website www.g0hwc.com / www.sstv.org.uk
------------------------------
Message: 2
Date: Sun, 20 Apr 2008 11:06:34 -0700
From: Terry Conboy <n6ry@arrl.net>
Subject: Re: [Antennaware] building a TAK-Tenna ???
To: Paul Young <paul@g0hwc.com>
Cc: Antennaware@contesting.com
Message-ID: <7.0.1.0.2.20080420104247.04a98e20@arrl.net>
Content-Type: text/plain; charset=us-ascii; format=flowed;
x-avg-checked=avg-ok-5D193B82
At 04:03 PM 2008-04-12, Paul Young G0HWC wrote:
>I have been reading up on the TAK-Tenna and would like to build one
>for 20m and 40m. Anyone for the details for this ?
>
>Also, anyone tried building a 80m TAK ?
There has been some discussion about the Tak-tennas on the TowerTalk
list. Start at
http://lists.contesting.com/archives//html/Towertalk/2008-04/msg00319.html
The comments from K4SAV are especially pertinent.
The conclusion is that the "antenna" serves to drive currents down
the shield of the feedline, which actually does the vast majority of
the radiating. Tapping the two "pancake" coils asymmetrically
adjusts the coupling to the coax shield and lets you get a good match.
On 40m, the radiation resistance of the antenna itself is only a few
ohms, most of which is copper loss, since the radiation resistance of
such a small dipole is less than an ohm. The bandwidth is also very
narrow, which is typical of small antennas, regardless of the loading
method. If a choke balun were used at the feedpoint of the Tak-Tenna
so the feedline isn't part of the radiating system, the SWR would be
very high, even at resonance.
On the good side, for a very small antenna, this is a relatively
efficient design, since capacitive/inductive hats of this type do
tend to raise the radiation resistance near the maximum possible for
a 30 inch radiator. But the reality is that the bandwidth will still
be very narrow even after matching (with a hairpin, etc.) and
decoupling the coax shield.
I have some EZNEC models for 40m, which include the coax shield, if
anyone is interested.
73, Terry N6RY
------------------------------
Message: 3
Date: Sun, 20 Apr 2008 15:42:40 -0400
From: "Gedas" <w8bya@mchsi.com>
Subject: [Antennaware] OT XM240 Loading Coils
To: <AntennaWare@Contesting.com>
Message-ID: <00e901c8a31e$b1bb5610$0401a8c0@ham>
Content-Type: text/plain; format=flowed; charset="iso-8859-1";
reply-type=original
Does anyone have handy the inductance value for the loading coils on the CC
XM240?
Gedas
W8BYA
http://gedas.cc
http://www.w8bya.com
------------------------------
Message: 4
Date: Mon, 21 Apr 2008 10:10:54 -0400
From: "Howard W3CQH" <hsgorden@comcast.net>
Subject: [Antennaware] Grounding needs
To: <antennaware@contesting.com>, <antennas@mailman.qth.net>
Message-ID: <016401c8a3b9$850d0780$6401a8c0@HAMSHACK>
Content-Type: text/plain; format=flowed; charset="iso-8859-1";
reply-type=original
I live in a 1 story home with a accessible attic.
I have an Icom AH-4 tuner mounted in the attic, and need to run a real
ground to the 8' ground rod we just pounded in.
My question is - should the ground wire coming from the AH-4 be of a wire
gauge of #12, or should I consider running 1/4" copper tubing? The total
length of the run is approximately 30'
73's
------------------------------
Message: 5
Date: Mon, 21 Apr 2008 09:41:27 -0500
From: "K9AY" <k9ay@k9ay.com>
Subject: Re: [Antennaware] Grounding needs
To: "Howard W3CQH" <hsgorden@comcast.net>,
<antennaware@contesting.com>
Message-ID: <015c01c8a3bd$c802eb00$6401a8c0@SUMMIT1>
Content-Type: text/plain; format=flowed; charset="iso-8859-1";
reply-type=original
>I live in a 1 story home with a accessible attic.
>
> I have an Icom AH-4 tuner mounted in the attic, and need to run a real
> ground to the 8' ground rod we just pounded in.
>
> My question is - should the ground wire coming from the AH-4 be of a wire
> gauge of #12, or should I consider running 1/4" copper tubing? The total
> length of the run is approximately 30'
>
Howard,
At a length of 30 feet, there is no RF "ground" -- it's nearly 1/4
wavelength at 40M and will always be part of any antenna connected to the
attic-mounted tuner. If you include the ground wire in a computer model of
the antenna, this will be quite obvious. I have three suggestions:
1. Install the ground wire as short as possible, with as large a conductor
as is practical. If the tuner and antennas work as you expect, you are
finished.
If the antennas fail to perform as expected, or if the tuner behaves
erratically, the new wire has created an unwanted resonance and/or increased
the RF levels at the tuner. One of the two other options may work:
2. Add an RF choke in the power/control wires of the tuner -- ferrite beads
or a few turns of all wires through a large toroid. This will "disconnect"
the wires at RF.
3. Run multiple ground wires (e.g. 3) of different lengths to different
ground rods. This will create different RF paths with different resonant
behavior. Odds are that this will change things enough to reduce the
problem.
73, Gary
K9AY
------------------------------
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