I’m excited to try out a new antenna I’ve been working on. It’s an adapted take on a design by DJ0IP for a 160/80m antenna on an 18m pole. The original desin of this antenna (pictured below) is a top loaded vertical for 160 with an 80m Inverted L hanging from the side.
Here is the DJ0IP design, Credit: http://www.dj0ip.de/vertical-antennas/160-80m-on-18m-pole/
I will say early on that I am not an expert, just an experimenter. The M0SDV design is slightly different. There is no shared feed point, and No shared ground plane. Instead they are two independent mono band vertical antennas from the same mast. This is an 18m spider beam pole. The 80m vertical is 1/4 wavelength with 2x elevated radials approximately 3m above the ground. To allow for a wide spaced coil at the base of the antenna I have built a frame from plastic tube to separate the 160m and 80m elements by 1m.
The 160m antenna is a “T” vertical using approximately 17m vertically and each leg of the top hat is about 15m long. This is over a pre laid ground plane. You might be wondering what I have used for the ground plane. I am not sure how effective this will be but like I said, I am an experimenter not and expert. Due to lack of space in my garden my radials are between 16m and 20m long going is multiple directions. This idea is taken from M0MCX at DXcommander who has modeled vertical antennas and shows that having shorter radials can also be effective. To add to this, I have 2 earth rods approx 1.5m under ground. I am not sure about the effect of the earth rods, but if you know maybe you can email me with your thoughts. and because I had extra wire I decided to tune 1x elevated radial along the fence. This combines multiple techniques that I have used before. Over the coming weeks and during CQ160 CW I will test this antenna and work on improvements for future.
I should also mention that each antenna goes to earth when not in use to avoid interactions between the two elements. As I repeat over and over, I am an experimenter, not an expert. Please feel free to email me your suggestions and comments… but for now 73 es CU on 160!