In years past, I tried (unsuccessfully) to get the benefits of wire Bobtail Curtain. They always sounded so great (in books and online) – but I never found that they were any better than a low dipole – in fact they weren’t even as good as a dipole. W8JI has debunked their legendary status by saying a dipole is a better antenna – and I agree with him. But the model for three elements out of four 40M quarter wave verticals seem to share some characteristics of a Bobtail Curtain. The big difference – I have always been able to get the expected performance out of a 40M phased vertical array. So maybe – this is a variation that will work – I think it will, actually.
This morning I realize that three elements out of the four are in perfect alignment. The first two were spaced intentionally – because before I had the N6BT DXU-32 – with its 2 element 40M yagi, I had phased verticals using the Christman Method of phasing. This time around, I purchased the DX Engineering phasing box which I believe uses a Lahlum or other W8JI “crossfire?” method of phasing.
The array approaches a 2 element yagi up a half wave. Even the azimuthal pattern looks about like a 2 element 40M yagi up 1/2 wavelength (sort of)
Those plots were in the forward direction, with the phasing on one of the two elements that are active in the phasing scheme – and the third element which is parasitic.
With the phasing in the opposite direction, the gain is only between 1 and 2 dB in that direction, but that’s fine for such a fixed and “accidental” vertical yagi.
And the elevation pattern. Lets look at the broadsided pattern . . .
Not bad for a total “Happy Accident”.
Again – not bad at all given that I ordered the wrong verticals for my 40M DXE phased array, used them instead for my 160M RX verticals with the NCC-2 and then built my own 34.5′ verticals for the phased 40M array – as called for in the manual.
Just for reference, when I had the phased vertical array on the posts and radial system which is now being re-used 2 years after that was taken down – I did use hatted verticals and they worked fine. But that was with the Christman Feed method, and today I will be able to see how this new DXE method with full sized quarter wave verticals works, I can’t A-B this of course, but as a reference, I remember the 2 element 40M phased array was about equivalent to a 40M dipole up close – but not quite as high as a 1/4 w.l, but of course with very good F/B – meaning not a ton of gain but serious directivity.
EZNec is usually a good indicator of real world performance – once you get the model right. Since I went to not connected radials that are modeled .2, .3 or .4 feet above ground, the models seem to be “OK”. I’m going to guess that I will in fact see some of this modeled behavior, but that some I won’t be able to really notice.
Later today – when its u and running, I will report my findings. Another 60 degree sunny day here – December couldn’t be nicer. And one last thing – sitting on that N6BT DXU-32 while waiting a whole year for 3Y0Z and Glorioso “some time” after that was silly – I find that every two years I just have to re-do my antenna farm – its really the most important thing for me in ham radio – I really do get more satisfaction out in the backyard with antennas than I ever have chasing DXCC awards. The horse in the antenna, and the carriage is the DXCC program for me.