Antenna alignment in yard

[Nashua Area Radio Society]

Hello,

This spring I’m planning on installing some type of end-fed wire antenna from the peak of my roof over to a tree.  I have a few tall trees to choose from.

• One tall pine offers a magnetic alignment of approx 210 degrees.
• One tall Maple offers alignment at 180 degrees.

With a QTH in FN42et, which alignment angle would you choose?

 

Thanks,

Ryan

 

 

[Aron Insinga]

Those the broadside directions, as opposed to the directions the end would be pointing, right?

Can you also go between two trees?  (I know that means running the feed line across or under the ground, and lawn mowers are a notorious hazard to cables across the ground.)

Here are the two azimuth map generators on the web that I know of:

1: https://clublog.org/greatcircle.php generated  https://clublog.org/greatcircle.php?&sa=FN42&saa=1 (This is the one I use.)

2: https://www.wm7d.net/az_proj/az_html/azproj_form_long.shtml or https://www.wm7d.net/az_proj/az_html/azproj_form_short.shtml which generated this:

https://www.wm7d.net/az_proj/maps/1612368314.gif

[Nashua Area Radio Society]

Aron,

Thanks for the links & images.  Very helpful.

The 180 & 210 degrees is the direction the wire will be pointing (attachment points between my house & tree).

 

 

[Aron Insinga]

For a half-wavelength dipole, you’d want to add and subtract 90 degrees to get the directions where the signal will be the strongest.

However, I haven’t used a multiband end-fed antenna before, and this article says that the radiation pattern varies by the band: https://www.electronics-notes.com/articles/antennas-propagation/end-fed-wire-antenna/multiband-end-fed-half-wave-efhw-antenna.php.  I don’t know if that’s a practical concern or not.  The manufacturer’s instructions may have more specific information, or the ARRL handbooks may help.  And of course I’m sure others here have used that type of antenna and can provide better insight.

 

[Jwahar Bammi]

Ryan

To help me with such decisions I like to use a Azimuthal Map. My preferred site is  https://ns6t.net/azimuth/

I entered your grid square, and the resultant map is attached. You can read off directions labeled around the Map to give you an idea relative to the rest of the world how you will be oriented. Given wire antennas radiate broadsides you can see that the antenna would do well across the US, and Africa, but not so much UK/Europe. IMHO the difference between 180 or 210 is a wash in practical terms, I would choose the further/taller tree, if you can mount a mast at the peak of your house to elevate the balun and run a longer vertical run of the coax into your shack, then definitely use a very good choke at the end of the coax before you run it into your sack to choke off the common mode current that will inevitably be there on an end fed.

Hope that helps,

 

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[Hamilton]

Hello Ryan,

A low horizonal antenna is omni directional. Low is less than 1/2 wave high, the further it is below 1/2 wave the more Omni it is and the “take off” angle also increases. At or below 1/4 wave high in the lower bands it will be a omni cloud burner and good for NVIS.

You have to consider which band you are evaluating. A 1/2 wave on 40m is 66 ft while on 10m it is 15ft.

As the slope of the antenna increases it will begin to perform more like a vertical. The radiation will be more in the direction of the wire and less broadside. But the take off angle will be lower which is better for DX.

It would be easy to model it in 4NEC2. It is a lot easier to play with lengths and heights indoors on the computer than in the snow.

Many of us can help get you started with 4NEC2 or EZNEC2.

Step one is to decide what performance you want and in which bands.

 

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