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I have a 20M K1WA Array up, and just for laughs decided to try a Bruce Array on 20M - hanging from 4 Jackite poles - with 4 elements and the bottom up 6' off the ground. The feed right now is as a vertical dipole on one of the center elements - ladder line perpendicular for about 20' to a 4:1 DX Engineering balun and then coax into the shack.

It works so well that I'll probably take the K1WA down.

I am thinking of putting another Bruce Array up behind the first one - and feeding both with 3/8 wl coax stubs - so that it is like the K1WA - I will be able to switch directions since the 3/8 wl stubs effectively add 5% to the element that is not switched in.

The only problem is that I can only place the second Bruce Array 1/8 wl behind the first.

What do you think?

[KE6VG]

What! You found something you like better than your K1WA Array!

I have played around with half-squares and the same thing. Use one as a reflector and one as a driven element/ switching East or West using a relay. The spacing is that of a Yagi, not phased verticals. I think Cebik had something modeled on the site.
Did you try and model it?
Try the 1/8 wave spacing and tune for best F/B with a signal source located a few hundred feet away. Same as the K1WA array. Closer spacing = narrow bandwidth, but, good gain and F/B ratio.

A few years back I had a 4 element Bruce Array and remembered the excellent S/N ratio. That was in a noise free location - near the top of a ridge in Burton Valley in Lafayette - on 5 acres.

Now I live in a steep ravine in Orinda - not at the bottom - but pretty close.  And only .3 acre (hi hi). The worst thing about Orinda are all the high tension lines coming out from the very large PG&E substation. My 3 element SteppIR yagi was almost useless - especially at the bottom of the cycle - too much high angle noise and man made noise.

The K1WA Array was much better than the 2 element SteppIR, and now - the Bruce is even better. Same gain, but very noticeable signal with less noise.

I've read a few white papers that suggest that my 4.2 db gain on the 4 element Bruce can be improved by a full 3 db if I put a second one behind the first and feed it "somehow". I think just using the same 3/8 wl coax stubs will work.

Imagine 7 db from wire - you know I just have to try this (heh heh). If I get directionality and 7 db with wire - I'll have to drink some Radio Coteau Neblinas to celebrate . . . .

Hell, I'll have some tonight in anticipation of the success . . .

[KE6VG]

I was looking around to see if I could find the article I was reading. I came up with this one.
http://www.isy.liu.se/~mj/HAM/ANT/
But, I voltage feed not current. I think the same concept would work with any of those type of antennas. Just like the other arrays, just trim the coax until you get best F/B or gain

I planted 7 Mexican Fan Palms across the back of my property a couple of years ago. Spaced 33' apart from each other. Broadside is E/W and the lot across the back is 214'. The neighbor behind me has some that have been in for years and they are 75'-80' tall. In a couple of more years I plan on putting up a large Bruce array, bobtail or edz up there.

Planting trees that way - very cool indeed! The 20M Bruce Array works very well - I had a large pileup of JA's and UA0's yesterday after I answered a JA's CQ and had a QSO.

I know - these aren't big DX, but each said my signal was pounding in - strongest on the band, so that made me feel good enough.

If I can snag Djibouti with this in 2009 - that will really be something. That's the only entity on that I need. Sunspots would be nice - but if Djibouti would come on 40M during our greyline - I might have a chance. But those guys seem to like to stay on 20M.

73,

Rich
KY6R

Here is a picture of the new 20M Bruce Array - 4 elements, 6 foot off the ground - on 31' black "Jackite" poles. Looks surprisingly nice in the backyard - next to the creek down below!

http://www.flickr.com/photos/ky6r/3317902794/

[KE6VG]

It looks clean. Similar to my half-square setup for 40m. I may just give this a try for 40 meters. The problem I have with the half-square is the narrow bandwidth. Did I say narrow! About 100 KHz 2:1 on 40. I have to go out and retune to switch over to the SSB portion of the band. I heard the Bruce Arrays are very wide bandwidth. Are you just runing the balun to coax and into the tuner of the rig? Or can you find a spot on the vertical element that you could get a good match to 50ohms or use the 4:1 or 8:1 balun. I want to be able to run at least 1000 watts into it. The other problem with the half-square is that long unsupported 1/2 wavelength of wire between the two poles. I have plenty of room for wire, but antennas like this or the half-square are really easy and cheap DX antennas for people with a fence line and even CC&R restricted people. I don't know why so many people complain that they can't put up anything decent for DX.

I fed one of the inner elements as a vertical dipole and ran ladder line to a 4:1 DX Engineering balun (their heaviest duty). Then coax into the shack.  Its band width is as advertised - a good 200 khz. My rig is the FT-2000D (no linear), and the rig has the stingiest tuner. The antenna easily tunes up to cover the entire CW and the entire SSB 20M bands.

Surprisingly, it works very well on 30M. My old 40M version worked like a champ on 40M and also on 12M.

The best comment by an author of antenna articles (Rudy Severn) is "this is an antenna that just seems to want to work").

I couldn't agree more.

[LID2LID]

In his SCV Notes book, W4RNL shows how to feed a 4 element Bruce with 50 ohm coax.  The two center verticals are fed with 93 ohm coax (RG-62) to a center T, then 50 ohm coax back to the shack.  Same pattern as the normal ladder line fed 4 element arrays, and 2:1 SWR over the entire 40m band (the model is for a 7.15 MHz Bruce).

I've never actually built one, but I'm considering it (or something like a switchable half square beam).

There are lots of good ideas in that book, but there is nothing on phased or parasitic Bruce arrays (there is usually at least some info on parasitic arrays of the other types of SCV's).

I've built and used one on 40M at my old QTH and 20M now. The feed is simple - 10' of ladder line from one of the two inner elements to a 4:1 balun and coax into the shack. At my old QTH I ran ladder line to a remote SGC autotuner. The 40M antenna worked very well on both 40 and 12M, and this 20M version works very well on 20 and 30M.

Best wire antenna I have ever tried - the K1WA array comes in second.

[LID2LID]

I think I'm going to build a 2 element Half Square beam for 20m.

I modeled a 20m Bruce at about 6ft height for the bottom (like you described), along with a HS beam at about a little over 3 ft at the bottom.  Jackite or similar support poles could be used for both, but I may just wind up trying the HS with telescoping aluminum to avoid guys (I don't have any suitable trees or other supports to hang a wire from).

Based on the model I put together, the peak gain for both was at a 20 degrees takeoff angle, but the HS beam had 1.5 dB gain (and slightly better gain at angles below that than the Bruce), wider beamwidth, and it's not bidrectional like the Bruce (though it can be switchable like with a relay).  It also fits better in my yard for the directions I want (35' width vs. over 50' for the Bruce).  Based on those reasons, I think I'm going to give the HS beam a try.

I'm not a modeling expert, but it does look promising to me.  You may want to take a look at it if you're wanting more gain than your 20m Bruce in a wire antenna for DX.

Its funny, I've tried half squares - and even a Bobtail curtain - the bobtail voltage fed with a really great home brewed LC network, and didn't see the gain that I had expected over a dipole.

I have seen the gain with the Bruce - and more importantly - for my QTH, the S/N ratio eliminates the swampy static noise I used to get with my old 2 element steppir yagi that I had up 40+ feet.

How did it work for you?

[W8JI]

Its funny, I've tried half squares - and even a Bobtail curtain - the bobtail voltage fed with a really great home brewed LC network, and didn't see the gain that I had expected over a dipole.

I have seen the gain with the Bruce - and more importantly - for my QTH, the S/N ratio eliminates the swampy static noise I used to get with my old 2 element steppir yagi that I had up 40+ feet.

How did it work for you?

I've had Bruce arrays in the past, but never liked the narrow bandwidth and never saw the expected gain. Of course mine were 80 meter Bruce arrays, so bandwidth and wire loss resistance was more important than the same array on 20 meters.

That aside, 5% does not a reflector make. As a matter of fact dead on resonance makes a pretty good reflector. Try it and see, and you will see I am correct. Take a dipole and tune it by itself to resonance. Now short the feedpoint and put a second dipole you feed in front, and you will have a nice backfire null. What you will find howevere is the reflector, from mutual coupling, causes the front dipole you are feeding to shift downwards in frequency for most spacings. The front dipole needs shortened a bit usually.

As for the reflector, you would be better off to make it a series of dipoles bent in the proper shape or a screen. This would be much better than trying to parasitically excite a long series element array!  You could add a second element and tune it with a tuned circuit or stub for rear null. I would not count on just adding a 3/8th wave stub unless you are one very lucky person.

http://www.w8ji.com/curtain%20sterba%20USIA%20array.htm

73 Tom