My quick and dirty hockey stick single bay Hoverman performed so well that I decided to try building a more permanent double bay. I used a 1 " square 6' aluminum pole to build the project on. I cut 1/4" threaded rods for the stand-off which I made of fiberglass tension rods. The reflectors are cut pieces of old I-beam curtain rods. They're held in place by two pieces of tension rods. Notice one pair is too short since I ran out of material although I'm skeptical that the reflectors actually need to extend 8" beyond the pickup wires. To hold the wire better in place on the cut pieces of tension rods I filed grooves which I'd recommend to anyone trying this project.

I wish I owned a drill press for this project. It would have made my life much easier for this project. Also, I found straightening and bending the aluminum to perfection by hand to be more difficult than I expected it to be. A bending jig of some sort would have been quite useful (and probably easy to make, 7 screws in a board of wood).

I was slightly disappointed in the performance of the antenna. It was better than my hockey stick single bay version but not vastly better, at least in a way I could measure it without the necessary equipment to measure gain. I did see the gain boost in the upper UHF range that I expected. I do wonder whether there was a performance benefit in using a non-conductive backbone for the the hockey stick version.

http://i237.photobucket.com/albums/ff4/pwalke2007/Hoverman.jpg

http://i237.photobucket.com/albums/ff4/pwalke2007/Hoverman3.jpg

http://i237.photobucket.com/albums/ff4/pwalke2007/Hoverman4.jpg

I get a lot of emails asking if I'd consider selling kits for SBGH/DBGH antennas. Well, right now I make a decent income from hacking the Linux kernel, so, no, not this month, thanks. ;)

But if there are people here in the Ottawa area who want help in making an SBGH or DBGH, then perhaps we could get together to share tips/techniques. There's still lots of that 5/16" aluminum rod available (Cohen&Cohen), and the fibreglass tubing and flats are still available at the local Lee Valley Tools store.

Apart from that, you'll need some threaded rod (10' lengths for $3-$4 at Ottawa Fastener Supply) and some nuts, bolts, and washers. Use wood, or square aluminum tubing (best prices at Princess Auto) for the backbone. I use round tubing here, simply because it's what I have in stock, but it is more difficult to work with than square tubing.

For the zig-zags, I'm currently using 1/8" galvinized steel fencing wire from Home Depot. Cheap, and holds its shape well enough for outdoors.

Cheers

Let me first say, you guys do very nice work, mlord and Scarborough. The only thing that concerns me in using a metal mast and the metal bolt between the elements method is that it upsets Autofils design. From what I can figure, his elements and reflectors have been designed in a free air space. (Tell me if Im wrong). By having a metal mast between the 20mm gap reflectors (or any metal), it seems like it may defeat the purpose of the gap by some extent. Same goes for the metal between the elements. Heck, Im even concerned about the brass screws I used in holding the reflectors and may replace them with nylon bolts.

I wish I owned a drill press for this project. It would have made my life much easier for this project.

Yep, a cheapie variable speed (by belt) chinese drill press is very handy, as long as you dont abuse them. I bought mine about 10 years ago for either $19 or $29 10 years ago. And despite rusting in the garage, it runs like a champ. Its main body is exactly like what Sears sells for $119, except it doesnt have the pretty Craftsman covers, its more utilitarian. Check places like Harbor Freight, they have deals like that.

Also, I found straightening and bending the aluminum to perfection by hand to be more difficult than I expected it to be. A bending jig of some sort would have been quite useful (and probably easy to make, 7 screws in a board of wood).


Just a couple of #8 finishing nails just tapped in, in a 2 X 12 X 4ft piece of pine conveniently placed, made my work easy.

All of you guys are doing really nice work on making DIY antennas. Love to see it. I doubt if the metal standoffs will affect the general performance of the antenna. However, I would recommend copper or aluminum for the array instead of steel, it doesn't rust (and lasts longer) and is not a lossy at RF. You can get #10 copper out of house wiring and #6 copper from grounding wire. The larger the better, especially for the reflectors.

DogT

This is a very interesting topic. I have a couple of questions.
Does the wire have to be bare? For example, could I use home wiring without stripping the insulation?.
Could you use copper tape on a window? Or would the capacitance throw the antenna out of whack?
If the window was a few degrees off, could you "steer" the reception lobes by altering the dimensions of the elements?


Im not an antenna engineer, but have been playing around with building antennas off and on since the early 70's, (mostly off). When you live 61 miles from the transmitters, you do dumb stuff like that. Take my advice if you want, or leave it.

Bare, NEW, copper or aluminum wire always seems to work best. Although I did build that huge Popular Electronics log-periodic VHF antenna years back that I used 14 gauge covered wire and it worked OK, I always had that nagging feeling that if I had stripped it, it would have worked better. So I do feel you lose a little db gain with covered or old wire.

Copper tape on a window will of course work, but keep in mind other variables, like the metal ?? window track frame, or cast iron sash weight, etc. And make sure its real copper tape, not plastic colored copper tape.

Steering by shortening or lengthening the elements has never ever worked for me, and has only reduced overall gain. Small, meaning tiny, directional change may be possible by tilting/angling the reflector.

Also, in doing what youre suggesting, and if you have storm windows, you may luck out if the distance between the storm window and the regular window is about 4 inches. Put the copper tape elements on the storm window, and use aluminum foil on the regular window for a reflector, if you catch my drift. If youre not far from the transmitter, you may be perfectly fine without being "head-on" to the transmitter. Look at the gain pattern graphs earlier in this thread.

All of you guys are doing really nice work on making DIY antennas. Love to see it. I doubt if the metal standoffs will affect the general performance of the antenna.

Thanks DogT, your antenna pictures were an inspiration to me. Yes, I also love to see the work and thoughts of others. You also used no metal standoffs in your antenna. It would be interesting to see a side by side comparison of plastic vs metal stand-offs, it may just be very minor. Hows your antenna working out ?

I would recommend copper or aluminum for the array instead of steel

Yeah, I'm using 5/16" aluminum rod for the reflectors, and my first SGBH/DBGH used 1/8" aluminum wire for the zig-zags. The the aluminum wire is not nearly stiff enough for outdoors here, and thus far the thickest single-strand copper wire I can find is #10, which is about equally soft as the thicker aluminum.

So steel for now. I may use the 5/16" aluminum for the zig-zags on the double-DBGH array that I hope to assemble next month. But that will require adjustments in the design to account for the thicker elements.

Cheers

It would be interesting to see a side by side comparison of plastic vs metal stand-offs, it may just be very minor.

The effects of the metal mast + feed supports are very likely to be negligible. Since we're after horizontally polarized signals, anything that's vertical or front-to-back horizontal is going to be more or less invisible (not 100%, but not likely significant) in the design.

And there is nothing but air between the reflector rods in the antennas I've made, though yes there is metal mast above and below the rod ends.. but not between them, nor within 5/32" of them at any place.

At some point, theory has to meet engineering reality -- a metal mast is pretty much required for tower mounting in any kind of weather zone. :)

But I did go a week ago and get a bunch of nylon nuts/bolts for attaching the zig-zags on my next version. :)

Meanwhile, things are getting crowded up on the tower here..

http://rtr.ca/recent/antennas_bw.jpg

But I did go a week ago and get a bunch of nylon nuts/bolts for attaching the zig-zags on my next version.

Mmm.. and there is a way for me to avoid the threaded rod inserts in the stand-offs for the zig-zag mounts. If I wanted, I could use epoxy to glue short nylon bolts into the ends instead of threaded-rod running front to back.

Mmm..

Heres a picture of a stub support that works pretty well : http://img516.imageshack.us/img516/3928/cabletiesupportko6.jpg



I made it from one of those big thick (5/16 in wide) screw on type nylon cable ties. I drilled a 3/8" hole in it for the rod and a 5/32" hole for the element. It helps keep the stub area at the correct spacing and adds some stiffness.

I made it from one of those big thick (5/16 in wide) screw on type nylon cable ties. I drilled a 3/8" hole in it for the rod and a 5/32" hole for the element. It helps keep the stub area at the correct spacing and adds some stiffness.

Mmm.. that's a cute trick for solving the spacing problem. I suppose I could combine that with some kind of horizontal strap to help prevent sagging.. the result could be quite good.

Cheers

But I did go a week ago and get a bunch of nylon nuts/bolts for attaching the zig-zags on my next version.

Speaking of which.. just simple cable-ties would probably do that particular job every bit as well as nuts and bolts, without any metal to speak of.

(..goes off to update notes for the next build..)

On the subject of spacing and sagging, I attached two aluminum rods vertically (behind and one on each side) to the reflectors with clothes pins so that it was touching all 6 of them. I found it neither gave me more gain nor decreased the reception. But it did even out the rods so they were all perfectly in a row, and the correct spacing could be maintained and make the whole unit a little more solid.

I only tried the vertical rods at 2 positions, one approx 5 1/2 inches from the center of the mast, so that the rod was directly behind the bend in the zig-zag and the other position at approx 9 inches from the center of the mast. The one directly behind the zig-zag seemed to perform a teeny bit better, but it was very hard to tell subjectively, and if so, only by a teeny amount.

I also covered the reflectors with cheap 12 inch aluminum foil (while the wind stopped blowing), still maintaining the 20mm gap, to make a full reflector. I saw very little improvement, so the 6 rod reflector seems to work quite well.

Wow.. reception last evening was superb here -- the stars (or sunspots) must have been in good alignment for a change. :)

The puny SBGH, mounted low on the tower (see illustration above) was pulling in the very distant WNPI(18) analog with just a little amount of snow. And that with no pre-amp at all! This is by far the best performance I've seen with any unamplified antenna here.

The 16-bay dual PR-8800 array, higher up on top of the tower with a 0.4dB noise figure masthead LNA, got totally noise-free reception at the same time (no surprise). It probably could have locked onto the much weaker WNPI-DT(23) too, but I didn't try.

All of which bodes well for a dual DBGH array (to replace the dual PR-8800) planned for next month, once more of the design parameters are worked out and simulated.

Cheers

Wow.. reception last evening was superb here -- the stars (or sunspots) must have been in good alignment for a change.I'd say you're seeing the kinds of springtime tropospheric skip and/or related DXing phenomena that others in your area have been reporting in the DX thread:

http://www.digitalhome.ca/forum/showthread.php?t=26789

Its a nice bonus, isn't it? :)

As such, it will outperform the commercial units below Ch 50-60, but seriously under perform above that channel range.

Surprisingly, my SBGH is outperforming the commercial units Im testing against on my channels 57 and 61, (which will go dark next February so its a mute point). I have a feeling the modeling program may not be taking into account harmonics, which is still fine.

Thanks for eveyones responses. I will make a SBGH and test against my bowtie. The bowties (2) I made were like the one at this well publicized site:

http://www.digitalhome.ca/forum/showpost.php?p=502262&postcount=76

It was great fun to make and I found out you can get really fixated on maximizing reception - location, rotation, height, etc. etc. My wife thinks I'm nuts!

Even without any amplification I am getting 16 channels and on a good day 49-1 and 49-2. Once built, I'll test the GH in in my attic and report any differences in performance I find.

Cheers.

Thanks DogT, your antenna pictures were an inspiration to me. Yes, I also love to see the work and thoughts of others. You also used no metal standoffs in your antenna. It would be interesting to see a side by side comparison of plastic vs metal stand-offs, it may just be very minor. Hows your antenna working out ?
300Ohm,

Thanks, the antenna is working fine. Although I am looking over 2 ridges, at 50 miles, so sometimes it is just not worth watching, but is a vast improvement over anything else I had.

DogT

The bowties (2) I made were like the one at this well publicized site:
For indoor use, you can follow similiar construction techniques with the hardboard/aluminum foil reflector and the 2 x 4 backbone with an additional 2 x 1/2 strip to get the 100mm reflector to element distance. (or rip a 2 X 6 to size) Just get the measurements and spacings right and dont forget the 20mm gap for the SBGH. Once you get the hang of bending/straightening wire, the SBGH is actually simpler to make.

For indoor use, you can follow similiar construction techniques with the hardboard/aluminum foil reflector...

I have created a solid reflector but kept a 20mm gap in the middle. I'm assuming that with a solid backing + aluminum foil reflector, one doesn't need to add the co-linear rods too? Is that correct? Thanks.