The UrbanBeam at 56′ – with plots on 40, 30 an 20M
The UrbanBeam has a boom that is only 4′ – but at the end of its “wing”, it expands out to almost 6′ – so I modeled it at 5′ spacing – because the “trick” with the UrbanBeam is to emulate a longer boom – which you would need to get the 4 dB gain that a two element yagi normally offers. I think what you get is something more like 3 – 3.5 dB, which is really excellent given its small footprint, and especially because its a dipole on 40 and 30M. Above 20M I think it really looks like a traditional 2 element yagi.
Tony, K4QE reminds me where the gain specs are – I was so intent on seeing them in the specifications section I guess I had a “blind eye” to that performance tab. Tony writes:
…and click on “Performance” to find the gain and F/B figures.
BAND DBIGAIN F/R DB
Band dBiGain F/R dB
40 m 1.6* 9.55(F/S)
30 m 1.77** 9.63(F/S)
20 m 6.5 12
17 m 6.6 12.6
15 m 6.6 14
12 m 6.7 15.7
10 m 6.65 14.8
6 m* 6.15 4
* A full size dipole is referenced at 2.1dBi
** Measured SWR is 2.3:1 for this model on 30m
73, Tony K4QE
Dan, AC6LA has modeled the antenna and his plots show the best possible story:
Yes, it really is a 2 elemet yagi on 20 – 6M. Its got to be the most unique antenna in this small size – to many bands category. I think in many ways it could be the most “genius” antenna in the SteppIR line.
I wasn’t very excited about the moving parts – but then a while back I played with stepper motors and realized how reliable they are. Who knows – I might take SteppIR up on their offer to extend my warranty for another couple of years. I was very pleased to see the hardware was all good when I did my “preventative maintenance” this weekend.
On the other hand, if it ever crapped out – I would revisit the idea of a 2 element shorty 40 – I will cross that bridge when the time comes. Versatility or power on my favorite band – the band that works throughout a sunspot cycle – those are my two options. But I worked 3 new ones the other day on 20M in rapid fire succession, and 40M is not great for DX during the middle of the day, but 20M (and above) are good. So it does seem like the UrbanBeam is what will help me most get to the FREQ 300.
Geez – I guess if and when this does happen I will also be closer to retirement – so where I end up moving also will factor into this. I guess I kind of expect that the UrbanBeam will be what I have here in Orinda for my last years here.