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Month: July 2016

antennas

Over the weekend, I put together a few simple antennas and hung them in my attic. The first was a 20 meter dipole, the second was a planar disk antenna.

20 meter dipole

For the dipole, I used 1/2 inch pvc pipe as the insulators and 14 gauge stranded THHN for the elements.

First, I cut a few pieces of PVC and drilled holes to feed wire through.

dipole_parts

For 20 meters, using the formula, Total Length = 486 / Desired Frequency, I ended up with 16.5 ft for each leg of the dipole. I cut the wires with a little extra to spare, and stripped the ends. I fed the ends through the center PVC and twisted it back on itself. Do this for both sides.

dipole_center

Next, I wound a balun. I followed this guide for a 1:1 balun. I can’t say for sure if the balun is correct or is working properly at this point since I don’t have a transmitter and can’t check the SWR. Once I build a 20 meter transmitter, I should be able to test and adjust, but the antenna is receiving okay which is all I need it to do for now, so I will leave it as is.

dipole_balun

I connected the elements to the balun as depicted in the guide linked above I used RG174 coax since that is all I had at the time.

dipole_center_balun

I soldered everything together and taped it up for strain relief. Since it is going in the attic, it won’t be subject to much movement so I’m not to worried about its structural integrity.

Next I added the insulators to the end of the elements.

dipole_end

I just twisted the wire around it self. I left everything exposed and unsoldered so I can tune it later. I then quickly dehydrated myself drilling holes in the attic in the middle of summer and running cables through the walls.

Planar Disk Antenna

I used two 12″ steel pizza pans from the dollar store and bolted them to a piece of wood with a tiny gap between them. Using the same RG174 coax, solder the center to one pan and the shield to the other and thats it.

planar_disk

planar_disk_2

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