WTB: Three AB-577 Extension Tubes

55′ is the best “Nominal” height for the UrbanBeam for 40 Meters

This time around, I will have a SteppIR UrbanBeam on top of the tower, also without a rotator – and I will rotate the antenna from the base manually. I have found that pointing the antenna in one direction – for weeks or even months – works like a champ. The standard kit (which I picked up yesterday), has 8 tubes – because I don’t use the “carrying cage” as the last extension tube, the height overall is 40′. I do have a 6′ double walled aluminum mast that I can attach to the top,  so even if I could find 2 extension tubes, I could get the UrbanBeam up 55′ – which is a very good (lowest) height for a 40M horizontal antenna. The gain, takeoff angle and pattern aren’t that much better at 60′, so even if I can only find 2 AB-577 extension tubes – that would be fine.

On 20M, at 55′ the takeoff angle is quite low – 15 degrees

I looked at 30M and 20M and they both benefit quite a bit from the height going from 34-ish feet to 55-ish feet. So, that’s the plan. I will keep the ALM-31 because it should fit any neighborhood I move into when I retire – not sure about the AB-577, but I will avoid CC&R’s and HOA’s like the plague when I retire. My parents had the “HOA Police” on then about the cut of their lawn – which I thought was disgusting – HOA’s and CC&R’s can go shove it. I have none of that here – I made sure of that when I purchased my house.

2 Comments on “WTB: Three AB-577 Extension Tubes

  1. You might want to consider simulating your results using HFTA. With horizontally polarized antennas, the ground terrain has a really big effect on the overall antenna system performance. You may be surprised.

    Liked by 1 person

    • I have done a pretty complete HFTA analysis, including HFTA Sweep. The hills all around me prevent any really low DXing, so the 55′ level at 40M is right, but for some of the higher bands I might even be going too high up (lowering the TOA too much).

      But on 40, 30 and 20m, I should be fine. I basically need to keep the TOA at 20 degrees or higher to get over the hills from my “bowl QTH”

      Like

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