Here's the only pic I have of either of them, this is the 40m fixed Giza, taken in 1984:
You probably can't tell a lot from this, but as you can see I didn't use any spreaders. The original plan had been to use a 40 foot mast for a support and have two equilateral triangle elements. I was a college student at the time and doing it on the cheap though, and used 4 chain link top rail sections instead of an expensive (to me) telescopic mast, and the bottom one buckled when I tried to raise the whole thing. So I had to use a 30 foot support and change the shape of the elements a bit. The bottom corners of the delta loops were tied off to the wooden fence on one side, and to 4x4 posts on the other, which are out of this photo. The pole was guyed at 10 and 20 feet with heavy crab net twine, and if you look closely at the top you can see the insulators at the apex of the loops. They were just hoisted up on guy bolts using light nylon cord. Coming in from the right is the RG-8 coax, and you see where it meets the 1/4 wave of RG-59. The feedpoint of the driven element is about 9 feet off the ground and was pulled in toward the center a bit.
I wrote a letter to K2GNC (this was before email!) telling him about this antenna, and he was surprised someone had actually built one for 40m. He commented that the performance of this configuration might actually be better than what he built since more of the elements were spaced farther apart. So where this antenna differed from his in the article was:
1. Loops were a driven element and director (to save space), no stubs
2. Elements were insulated from the mast
3. The triangles were altered ("squashed") for the reduced height.
4. 1/4 wave 75 ohm Q section was used instead of the gamma match.
So how did it work?
Compared to a 135' Windom at 28 feet that was about 60 feet away from this, the first thing I noticed was how much quieter it was on receive. Texas City, Texas is full of chemical plants and refineries, and the noise on 80 and 40 is pretty bad. I had a pair of phased verticals for 20 meters that had worked well for me in Alabama but were all but unusable there for that reason. Bear in mind I had a single purpose for this antenna: to provide a more reliable link to an old friend in Alabama, which is why it was fixed in a ENE heading from South Texas. It did that job very well. The broadcast carriers from the Carribean were knocked down considerably as were the kilowatt amateur SSB stations from the north and west, and I was able to copy my friend's barefoot HW-101 and low dipole much better than on the Windom (and the Windom was a pretty good antenna, I thought). And as is the case with most beams, I could work European DX that I could not even hear on the Windom. Not bad for a 40m beam whose elements were barely 6 feet above the ground in a couple of places.
I don't have a graph (this was 25 years ago), but I recall the VSWR being below 2:1 across the entire band. It would also load fine on 15m, but there's no telling what the pattern was there, it didn't seem to be unidirectional. I could get it to load on 20, but didn't use it there in deference to the sweep tubes in the Drake.
The 10m version was closer to what's in his article, though I again used a DE/Director. Aluminum tubing and angle from a local hardware store was used for the mast and "spider", and 1/2" PVC was used for the spreaders (which made the antenna heavier than it could have been, but it worked OK). I had a bunch of good quality RG-59 and decided to use that as a direct feed since I figured the impedance of that array (again, insulated from the metal support) would be in the 100-125 ohm range and should give at least a decent match. Nope, wrong. I didn't have an analyzer, but the VSWR was over 2:1 across the entire 10m band, so I had to revert to Plan B, which was to whip together a wire gamma match on the roof. Long story short, that took care of it and the coax capacitor ended up being only about 2" long.
This was only up on a 20' pole with a TV rotator, but compared to a 3/2 wave inverted vee at 30', it again was much quieter on receive. I'd had a 2 element quad in that same spot that I took down to mess around with the Giza, and from what I could tell there was no difference in the two as far as apparent f/b, f/s, or forward gain. All anectdotal of course, but I'd used the quad enough to know what to expect of it, and they behaved exactly the same-- the only difference being the quad was fed with a 1/4 wave Q section and had a little wider VSWR bandwidth than the Giza with its gamma match. And as with the 40m Giza, I worked a lot of VKs and ZLs I could not even hear on the inverted vee.
So there's what I can tell you about the two Giza beams I built. The only issue I'd take with the original article is that he says it does not matter whether or not the loops are insulated from the support. That might be OK if you used wood or fiberglass, but it seems to me the elements would have to be insulated from metal.
Another thing I've mulled over is that for a 20m Giza, the vertical support will have to be about 20 feet high. That's too much for 6" bolted into a light duty rotor to support. A TV rotator would probably handle a 20m Giza in the wind, but a thrust bearing would be helpful, and allow maybe 18-24" below the antenna to rest in that.
That's all I know, guys. They're cheap enough to build and don't require any special materials, just a wire antenna. I used 20ga stranded insulated hookup wire for the 40m behemoth, and 16 ga insulated auto wire for the 10m version.
Rick
