The SteppIR UrbanBeam re-purposed as a 2 element 40 and 20 Meter yagi
Since the lions share of my DXCC Honor Roll DX was achieved on 40 and 20M:
More than the actual totals per band – if you factor in QSO’s made across the entire Cycle 23 time period, 40 and 20M are the clear winners.
40M was the absolute “savior” at the bottom of the last cycle. It became my favorite band partly because of that – but also because it seems to always have at least something going on every day or every year of every point of the sunspot cycle. Just checking into a regional net in the Winter has always been fun – if say, DX is scarce. But the Winter Long Path from the West Coast to ZS, Middle East and EU is just the best possible DX – very low noise – and great signals making the toughest parts of the globe easy to work.
By adding two strong fishing poles to the UrbanBeam, it would be very possible to achieve a boom length that puts the antenna in the 2 element “shorty fourty” range. The F/B would end up being only 12 dB or so, but with some coil loading and hairpin matching (just like the N6BT DXU-32), I could probably get about 3 dB gain – only 1 dB down from that monster yagi that I used to have. On 20M – it would very much be a 2 element 20M yagi – probably with 16 dB F/B and 4 dB gain.
I would have separate feeds, but have a switching circuit using relays in the motor shrouds after removing the stepper motors. Remember – this is my “Plan B” – if my UrbanBeam ever ended up with dead stepper motors, and where the cost to replace would be more than I would care to spend.
The weight of the antenna would still be about half of the current 48 pounds. It would not look like a Hex Beam, but instead, the fiberglass would have a slight trussing action – keeping the antenna flat and looking nice and neat.
SO, it looks like I wouldn’t have to spend $1500+ on some shorty fourty yagi after all – and I could achieve a killer antenna even if the UrbanBeam one day died. Matching using a remote switching arrangement means one feedline, and I would optimize the spacing using EZNec. The antenna would be tuned for the CW band, so even if the 40M were somewhat narrow banded – due to some coil loading and hairpin matching – that would be absolutely no problem. And if I ever did get into FT8 – that would also be covered. If I used a commercial remote antenna switch – I could even switch in different coax stubs of 50 or 75 ohms and use baluns appropriate for such matching.
Gee whiz – SteppIR should sell such a “kit” – call it the “poor man’s UrbanBeam”. Currently, the UrbanBeam sells for $1946 – I think that is $200 more than what I paid for it. The stepper motors are $460 and $520 to replace, and the SDA-100 is $549. This means the fiberglass is basically $200 – something dollars – which in Kite Pole terms is about right.
Come to think about it – I would use the UrbanBeam’s channel – where the copper “stip” used to be to fish a stiff wire for 20M, then I would only have one “outrigger” wire to add – it would be quite “elegant”, and be a pretty damned great antenna:
The KY6R Urban4020WireBeam
All kinds of matching schemes could be tried, and making Hi-Q coils out of aluminum or copper refrigerator line would be cheap and easy. Since this would add weight, the frame could be slightly bowed like a Hex Beam – and where the 40M wires act as a truss of sorts. But the bow would be minimal.
Interestingly enough – there is a switching and matching arrangement already up at the antenna, so my work might be a lot easier than I think. Because the antenna is only 30′ wide – the 40M position would have to have the copper stip wire wrap around the frame with the other stip retracted for 40 and even 30M. Another option would be to use the frame to wrap a 40M folded dipole wire and then have the 20M wires outside the frame – and where no “outrigger” or additional fishing poles would need to be added.
There are many options and room for a lot of experimentation. The best thing is having a “Plan B”- don’t get me wrong – I love my UrbanBeam, but might not bother replacing stepper motors if they ever fail – and one day they most likely will. I have heard 10 years is not too much to expect out of these – so with only a year or two in – I am sure I will be in the middle of moving (retiring) by the time that happens anyway – so all of this could be moot.
Time will tell.