With winter approaching it is time to make improvements to my antenna setup for 160m. The current Inverted V with its high angle of radiation works very well within the Midwest and serves me well for evening rag chew sessions with the surrounding states.
Operating in last years 160m phone contest I experienced less than ideal performance out to the coasts and DX was out of the question. Reviewing the options verticals are the way to go and given the structures already in place an inverted L is the best option.
For success any vertical antenna needs a radial system, the better the radial system the lower the radiation angle and better the long distance performance.
Made a base from a hunk a scrap angle to which I welded a piece of scrap to keep it in the concrete as concrete shrinks when cured and it would be a bad thing for the angle to slide out!
Also welded a chain link to the top for tie off and made the structure a bit wider in the middle to provide a place to mount a plastic junction box. A plastic bucket and one and a half bags of concrete latter and presto a solid base which will not move around.
The junction box which I picked up at a big box hardware store has 4 holes it in, one on the bottom for the feedline to enter, one on each side to which the center conductor and shield is connected to use 1/4 inch stainless hardware with a neoprene washer on the inside. And a third which serves as a tie point for a ground lead.
A to do is a piece of stainless steel wire connected to the ground stud and held 3/8 of an inch or so from the antenna lead to act as a spark gap.
I also have provisions inside the box for a bleed resistor once I gather up the parts.
Visible here is the other side of the base, a piece of tinned copper strap connects the ground radials to the the shield of the feedline. A piece of soft drawn copper is used as a bus bar to which I have silver soldered the ground radials. Also visible here is the ground rod which is in at an angle as only 4ft of soil is present at this location.
In total 1600 ft of 14 gauge solid was used in the radial system, resulting in 16 radials each 100ft in length. Of the bunch 7 are buried in areas where vehicles and horses roam. The rest are held down every 5 feet or so with handmade staples from #12 fence wire. Plan is once the grass grows back they be locked into the turf and the steel staples with rot away.
I cut the antenna for 140ft and adjusted length and mid point to both center the usable SWR valley and too adjust the depth of the SWR valley. My minimum is roughly 1.4 with 100khz bandwidth at or below a SWR of 2. As a bonus all of the 60m channels have a usable SWR, and performance has been wonderful.
I would like to increase the vertical component of the L however my attempts to date has resulted in an unacceptable SWR. A matching network will been needed and this will need to wait for warmer weather.
73 until next time, Jay
Leave a Reply