I'd give it a try, Rick! I think that you are likely to be surprised and pleased with the results! Yagis ( or 1/2 Yagis) just want to work and are very forgiving of offset elements!
I've built 2 and 3 element 40 meter yagis in the past that were wonderful performers - especially on the morning and evening long paths. I've also added directors and reflectors around my parallel 40/30 meter vertical dipoles with really good results. (Just wires hanging in trees supported by fishing line! They worked well!) I also built an 80m 5-element steerable array for 80m (driver and 4 parasites that coul be remotely switched between reflector and director tuning with relays and stubs). That one was a FEARSOME, "killer" DX antenna! One of my proudest accomplishments! The driver and parasites were 1/4 wave verticals operated against elevated resonant radials - 4 for the driver and 2 each for the four parasites) You could put up an 80m inverted L for 80m, tuned as a director, and parallel it with a 40m 1/4 wave director and operate it against elevated resonant radials for 80 and 40m. You might need to play with it a bit in EZNEC to "jiggle" the element lengths for best performance. If you really want to "gild the lily", you can insert sorted stubs near the feed-point of the vertical parasites to tune the parasite as reflectors, and short the stubs with relays at the antenna elements to change to director tuning to make the 1/2 yagi reversible! - That's how I implemented the 80m steerable array - and it worked wonderfully well!! The array was steered with a switch box in the shack to control the relays. The deceptive thing about modeling vertical parasitic arrays, is that, because of the vertical polarization and the absence of "ground-reflection" additive gain, the gains that you will see in EZNEC are not so impressive compared with horizontal yagis. However, the on-the-air performance can be really impressive - especially on long-haul paths because of the low takeoff angle. I don't think that you are likely to accomplish much on 160 if you are limited to 10.5 m. Good luck! Have fun!! ( I really like modeling, building andplaying with high erformance antennas! :) ) 73, Charlie, K4OTV -----Original Message----- From: Topband [mailto:[email protected]] On Behalf Of Rick Kiessig Sent: Tuesday, November 05, 2013 9:45 PM To: 'topband' Subject: Topband: Vertical 2-element array? I have a quarter-wave vertical for 40m on a steeply sloped lot, at about 100m AGL, 300m horizontally from the ocean. It currently has a relatively poor radial field (more are in the works, of course); I use it entirely as a multiband receive antenna, not for TX. A second fan-vertical element is connected to the same feedpoint, configured as an inverted-L for 80m, which I do use for TX, but rarely. It's resonant on both 40 and 80, and works on 160 at low power with an in-shack tuner. Downhill, toward the ocean, is also the direction to EU and JA. On sloped land like this, is a second vertical director-like element downhill, below the first one likely to work (it would have to be limited to 10.5m height above ground)? If so, would it buy me much? EZNEC suggests a slight improvement is possible, but modelling this kind of system has been problematic for me in the past, so I'm not confident of the results. Are there other alternatives I should consider for increased gain on 40, 80 and/or 160? The horizontal space I have available above ground is very limited, so things like an FCP or a K9AY loop are too big. I could make room for a BOG or Beverage, but the longest run would be about 50m, and it's not really in the right direction. 73, Rick ZL2HAM / ZM1G _________________ Topband Reflector _________________ Topband Reflector
