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Author Topic: mobile 2M horizontal antenna  (Read 10905 times)
KJ4MYY
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Posts: 34




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« on: May 10, 2010, 07:54:30 AM »

I don't see many 2M horizontally polarized mobile antennas for sale.  I don't want to spend the money that M2 wants for a halo.  Does anyone know or have any plans to make a omni-directional horizontally polarized antenna for 2M that I can use for mobile use?
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WB2WIK
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Posts: 21807




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« Reply #1 on: May 10, 2010, 09:00:00 AM »

You could build your own horizontal omni like this one:

http://www.hamuniverse.com/loop.html

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KH6AQ
Member

Posts: 7718




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« Reply #2 on: May 10, 2010, 02:14:00 PM »

If you are looking for something simple, something that does not require tuning, a turnstile antenna is one way to go.

It is two crossed dipoles fed 90 degrees out-of-phase. If you need dimensions I can post them here.
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KH6AQ
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Posts: 7718




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« Reply #3 on: May 10, 2010, 02:16:08 PM »

There is also the 3-D folded loop turned on its side. Google 3-D folded loop. This requires an SWR meter to tune.
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KB5WIA
Member

Posts: 9




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« Reply #4 on: May 10, 2010, 04:13:36 PM »

If you can find a used or discounted M2 HO-Loop, go for it.  I've been running one for a few months now for SSB-mobile, it works very well -- high-quality construction and it's plenty rugged too.

73 de Dave KB5WIA
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KB2VUQ
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Posts: 125


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« Reply #5 on: May 10, 2010, 08:24:58 PM »

KU4AB http://www.ku4ab.com/2m-horiz.html

Although I experienced delivery problems with mine and was very skeptical
about the way Phil conducted business at the time (he was moving to another
state), I'd give him the benefit of the doubt, since he does make a nice and
affordable product and purchase from him again. My 2 meter loop works just
as well as any other loop.

KU4AB http://www.ku4ab.com/2m-horiz.html
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KJ4MYY
Member

Posts: 34




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« Reply #6 on: May 11, 2010, 04:19:05 AM »

Thanks for the info.  The KU4AB looks interesting, great price.  The problem for me building something horizontal and mobile is how to mount it or what to affix it to. There is no 3/8 stud or NMO mount that you can use for horizontal since the shield side of the antenna is needed for the other half of the antenna.  So I am not sure how I would make a mobile horizontal and mount it.

What are the dimensions of the turnstile antenna?
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KH6AQ
Member

Posts: 7718




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« Reply #7 on: May 11, 2010, 05:44:48 AM »

The turnstile elements are about 36".

The dimensions of the 3-D folded loop are 12 x 9 x 9 inches. I have one (the original) sitting on the desk. L.B. Cebik was the first to suggest using it as an omni-directional horizontally polarized antenna. Mechanically it is simple to mount horizontally or vertically. One 10' length of 1/2" copper tubing and 12 elbows.
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AA4TX
Member

Posts: 28




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« Reply #8 on: May 22, 2010, 07:29:39 AM »

Take a look here. I have 2, and am very pleased.

http://www.efactorantennas.com/index.html


KI4LTX
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K3GM
Member

Posts: 2413




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« Reply #9 on: May 22, 2010, 04:13:35 PM »

KU4AB http://www.ku4ab.com/2m-horiz.html

Although I experienced delivery problems with mine and was very skeptical
about the way Phil conducted business at the time (he was moving to another
state), I'd give him the benefit of the doubt, since he does make a nice and
affordable product and purchase from him again. My 2 meter loop works just
as well as any other loop.

KU4AB http://www.ku4ab.com/2m-horiz.html

X2.......I also have a short stack for 70cm too.
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GM0GTU
Member

Posts: 12




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« Reply #10 on: May 26, 2010, 04:27:47 AM »

Can someone explain to me how the Efactor antenna achieves a gain of 1.5 Db over a dipole?  It looks like a half-wave dipole bent almost in to a figure 8 shape. How do you make a halve-wave dipole have more gain without increasing the length?

Regards,   Stewart  GM0GTU
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N3OX
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Posts: 8915


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« Reply #11 on: May 26, 2010, 08:11:46 AM »

How do you make a halve-wave dipole have more gain without increasing the length?

You don't.
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73,
Dan
http://www.n3ox.net

Monkey/silicon cyborg, beeping at rocks since 1995.
WB2WIK
Member

Posts: 21807




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« Reply #12 on: May 26, 2010, 09:41:59 AM »

Can someone explain to me how the Efactor antenna achieves a gain of 1.5 Db over a dipole?  It looks like a half-wave dipole bent almost in to a figure 8 shape. How do you make a halve-wave dipole have more gain without increasing the length?

Regards,   Stewart  GM0GTU

The only way to achieve gain is to lose it in some other direction.  Normally a horizontal omnidirectional antenna, if it's truly omnidirectional, won't have any omnidirectional gain no matter how long it is: Gain comes by splitting lobes and creating nulls between them.  If you stack one above another and feed them in phase with proper spacing, you achieve omnidirectional gain by compressing the vertical pattern and losing gain at higher angles (which usually is fine).

However, "dBd" as a reference is confusing because it is often used as a reference to "free space."  In "free space" a horizontal dipole has 0.0 dBd gain.  However, over real Earth, it has real, actual gain "over a dipole" (in free space) due to the ground reflection reinforcement.  A 1/2-wave dipole over good, conductive Earth can easily achieve 6 "dBd" gain.  So, if the manufacturer is claiming "1.5 dBd gain" (over a reference free-space dipole), that's very believable, and about 4.5 dB less gain than a 1/2-wave dipole would have it its two favored directions.
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KH6AQ
Member

Posts: 7718




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« Reply #13 on: May 26, 2010, 04:30:02 PM »

Can someone explain to me how the Efactor antenna achieves a gain of 1.5 Db over a dipole? ...
Regards,   Stewart  GM0GTU

I see no numerical gain claims at the Efactor antenna website.
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N3OX
Member

Posts: 8915


WWW

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« Reply #14 on: May 26, 2010, 06:20:20 PM »

Can someone explain to me how the Efactor antenna achieves a gain of 1.5 Db over a dipole? ...
Regards,   Stewart  GM0GTU

I see no numerical gain claims at the Efactor antenna website.

It's in the text on the front page.

Gain figures of 1.5 dbd on 144 and 3.2 dbd on 432, this was verified at the Southeastern VHF Conference in 2005.

73
Dan
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73,
Dan
http://www.n3ox.net

Monkey/silicon cyborg, beeping at rocks since 1995.
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