Converting an UrbanBeam to a KY6R “UrbanWireBeam”
Before deciding on the SteppIR UrbanBeam, I seriously thought about the OptiBeam OB-10-5 http://www.optibeam.info/index.php?article_id=130&clang=1. I really like the looks of this wire beam much more than the Hex Beam. When you live in the suburbs – if you are lucky enough to be able to have an antenna up 55′ as I am – I also know that its important to make the antenna look as unobtrusive as possible.
What if the Stepper Motors in the UrbanBeam crapped out – and I did not want to replace them (they are probably expensive – in fact this antenna is quite expensive). The fiberglass is probably the cheapest part of the antenna, and its also the lightest weight parts of the antenna. I have had very good experience with wire Moxon’s in the past and have bagged many rare DX with a 20M fishing pole Moxon, so – I know a wire beam can be very competitive.
The “frame” of the UrbanBeam is 30′ wide, and the boom is 4′. The two elements spread out to somewhere in the vicinity of 6′, so this could be used as a frame for a Moxon on 17M. It also could be used as a rotatable dipole on 40M and a 2 element wire beam on any band 20M and above. I would follow the OptiBeam / Hex design and go with a wire beam. I would have a bent 2 element 30M yagi (that could be used as a 40M rotatable dipole), and then have a 20M yagi, a 17M yagi and a 15M yagi. Id be fine using it as a rotatable dipole on 12 an 10M.
Multi-banding an antenna is not easy – especially with adjacent bands, so I could even just work on 40, 30 and 20M if need be – since those are by far the most important bands. There are lots of options with this idea. Maybe a combination of 2 element wire beam, moxon and rotatable dipole could work. The overall performance might lose a dB on some bands, but my guess is that it would still be “good enough”.
By far, the heaviest parts of the 48 pounds that make up the UrbanBeam are the two Stepper Motors. I could take them out – and use the shrouds on the boom to devise a switching circuit using relays and coils – if that is even needed. The fiberglass would be used exactly as it is. I would build it to handle 1500 watts, but would be using it for 5 watts. Because the antenna would be more than half its current weight, I would most definitely add the last two AB-577 tubes and get the bugger up to 65+ feet up.
It was a leap of faith when I purchased the UrbanBeam, and in the back of my mind I have always wondered “What if one day I come into the shack and the motors or motor stops turning”? I like knowing that there will be no panic the day the UrbanBeam craps out – and that I have already figured out a way to reuse the antenna in a way that would perform on the bands I want as good as the UrbanBeam itself (on the few bands I really care about).