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Railfan Technology > A ground plain antenna you can build.

Date: 08/14/22 20:21
A ground plain antenna you can build.
Author: wa4umr

Here's a ground plain antenna that you can build for a few bucks and maybe 39 minutes (or less) of your time.  This design comes from a ham radio source but is easy to modify for railroad frequencies.  I've done the conversion for you.  

The vertical radiator should be 17-3/8"  The radials should be 18"
You can use #12 or even #14 copper wire if the antenna is in an attic but if it is going to be outside, I would use the brass rods.  If you are going to hang it in an attic, you can add an inch to the length of the radiator and fold back the top inch, and put a loop in it to tie a string to it and tie that to a nail.  The length of the radials does not include any loop you might put in them for mounting.  It is the length from the connector to the tip of the wire that matters.  It only shows two radials but there should be four.  You can connect the radials with some 4-40 screws and nuts or if you have a heavier enough soldiering iron/gun, you can put the wire through the mounting holes and solder them directly, assuming you have a quality connector that will accept the solder.   None of the measurements are extremely critical since you won't be transmitting however, the closer, the better.  The connector shown in this example is an SO-239.


Date: 08/15/22 08:50
Re: A ground plain antenna you can build.
Author: WW

What about grounding?  Especially if the antenna is mounted outside, the antenna should be grounded--and grounded to the same grounding that grounds the power source of the radio attached to the antenna.  

Date: 08/15/22 22:30
Re: A ground plain antenna you can build.
Author: wa4umr

I agree that it should be grounded.  I didn't supply any information about mounting it on a mast.  That would most likely be a metal mast and building a bracket to mount the SO-239 to that mast would most likely be a metal bracket.  The mast should be grounded to the same ground that everything else is connected to.  A lightning arrester wouldn't be a bad idea either.


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