US Towers ALM-31

Image Copyright US Towers

US Towers has a nice crank up aluminum tower / mast that would be perfect for the UrbanBeam. I also saw these up close at Dayton last May, and like the UrbanBeam – it caught my eye. At the time I was still fully focused on DXCC, so these products were put in the back of my mind.

Image Copyright US Towers

The strength and weight makes this perfect for my new “Post DXCC” situation. These two products that I saw at Dayton popped back in my mind as soon as I hit 9BDXCC and along with the cancellation of 3Y0Z.

One operating idea that I have also had – but which was also stashed in the back of my mind is the USA County Hunters Award. It would be perfect for the bottom of the Sunspot Cycle and also get me into serious “Retirement Hunting” as far as where we might retire to. Our first choice is Bend, OR, but I want to really consider as many places as I can. One example: a year ago we visited our relatives in Eugene and we stopped in Corvallis and Cottage Grove. We learned that Lane County has the most covered bridges West of the Mississippi. Having gone to college in PA, that was especially cool. We also rode our bikes past the Hop fields between Salem and Corvallis, which was another highlight. Chasing County Hunters would unfold quite a few interesting tidbits and stories.

I have no idea when I will retire, and expect to be in Orinda at least 5 more years. The nice thing about the UrbanBeam and this crank up mast is that I can take them with me when I retire – that’s why I do not want anything big and heavy. No big antennas or towers or amplifiers.

Its a good feeling to be looking at my next “chapter” – its just starting to barely form now.

40M LP and SP Take Off Angles

The F1 layer exists only in summer, and during the Northern Hemisphere Winter, our F2 layer means that we get more distance covered by each hop. At ZS they have both F1 and F2 because its their Summer.

ZS6CCY has a low take off, high gain antenna – 3 element yagi up high on 40M. This is why he always will be doing most of the work. Here is the Short Path:

My lower take off phased array works best after our sunset. I’m going to guess that my first hops – that would go over the US, would benefit if they did not bounce off land – so the lower angle prevents this. ZS6CCY has gain, low takeoff angle and salt water on both SP and LP for the first hops.

During the morning sunrise at my QTH, my rotatable dipole, with a higher take off angle does best – and I can only imagine it has more to do with me bouncing off water – and maybe its also because the F layer is rising. I’m still not sure why a higher take off angle is better . . .

Here’s another variable. My terrain. During the nightly SP – my east direction has an immediate hill that I have to try to go over. Why my lower take off angle antenna is best is a mystery. For the morning long path – I have a lower hill to get over.

  • Terrain seems to not matter
  • The charging of the ionosphere and the F1 and F2 composition seems to be one part of this puzzle
  • The fact that I am bouncing off salt water means whichever antenna supports more water and less land seems to be a second part of the puzzle

The wild card would be some kind of chordal hopping or ducting is happening during my morning sunrise. The higher angle would get the signal in the duct where the ionosphere is charging and rising, and it requires a higher angle to do so. If you look at the Long Path – both stations have sunlight. On the SP – both are in dark. This has to be a key variable. If I had to give my answer – I’d say chordal hop or ducting happens when both stations are in sunlight.

On page 49 of the Ian Poole (G3YWX) book “Radio Propagation – Principles and Practice”, this situation does seem to be a very strong possibility. He even shows a diagram where indeed – a higher angle would be helpful, and a low angle at ZS6CCY’s QTH would not matter.

 

Take Off Angle and HF Propagation

My 40M A – B tests between the DX Engineering DV-40-P phased vertical array and the Cushcraft D40 rotatable dipole have left me wondering. Why does the phased vertical array work better on the evening Short Path and the dipole on the morning Long Path to ZS.

This “oldie but goodie” paper seems to describe at least some of what is going on:

http://nvlpubs.nist.gov/nistpubs/jres/65D/jresv65Dn2p167_A1b.pdf

My guess is that the transmitting antenna that is more in the darkness needs a lower angle than when in light. 40M is interesting because it opens for long haul DX during the fading sun for a SP path, and stays open after sunrise for up to two hours depending on time of the year.

My rotatable dipole is up only about 40′, which means it has a significantly higher take off angle than the phased array. But because it is already light out – the lower layers in the ionosphere are charging up on my end or the circuit and fading on the ZS side via LP. On the SP – it is the reverse, but when I have QSO’s with ZS on the SP – my side is several hours into the darkness meaning I am probably using the combined F layers or even the E layer. There would be fewer hops on the SP than the LP – that’s for sure.

Because the LP is so much farther than the SP, I am going to guess that there could be chordal ducting going on. The signals are many times as strong as on SP – if they are weaker, its not by much. Something interesting is going on. The waves are traveling through a long and very dark path, but both sides of the circuit are not far from light – either fading or gaining.

I can’t find a definitive explanation – not in the ON4UN book, the Ian Poole book – or this paper. ON4UN does call out the LP path that I am discussing – because during deep Winter, my ZS morning LP extends as far as QSO’s that I have had in Northern Ireland!

I’ll keep looking for an answer – but this proves that doing A – B antenna testing is a very interesting and valuable thing to do.

Alas Poor DXCC (and QRO), I Knew You Well!

I’m going through my DXCC “withdrawal” – lets call it a DXCC 12 Step Program. First, I got rid of the N6BT DXU-32 (best antenna along with the DXE DV-40-P and Wellbrook ALA1530LNP’s) and AB577 Military Tower. Now I am getting rid of my 1500 watt amplifier and manual tuner and am going to go with the Elecraft K-Line from now on. I will also rely on resonant antennas with the Inverted L (that has my home brewed base matching circuit), the DXE DV-40-P 40M phased array, and soon – a SteppIR UrbanBeam for 40 – 6M. I have the KPA-500 and KAT-500, but the tuner is mostly a “line flattener” . . .

This is all a bigger commitment than I expected it would be – but its time to move on.

An Interesting Thing on DX Atlas

I just noticed today that the grey line part of DX Atlas just changed from yesterday to today. The light pattern is changing towards Spring. You can see the very first day towards the big switch from Winter to Spring in the Northern Hemisphere.

I added two Orange arrows to show where the change is happening first . . .

Linear Loaded Slanted Verticals

While it looks like an Inverted Vee or even a Delta Loop, it really is just two bottom fed verticals – bent over. The bottom wires are 8′ off the ground and the top 50′. The “wingspan goes out 35′ in each direction for an overall width of 70′. Its an update to the “Mod Bob” – but this time, with slanted wires and using some linear loading – where the bent back wires act as a sort of counterpoise, we get nice patterns (at least using EZnec):

The feed looks like a dipole, and I could even modify my base choke / UNUN switching circuit to switch in taps on the bottom wires – so you can be resonant on 160 or 80M without any loading components. I did not model the extensive 96 buried radial field that is under this – but I am sure that would only help.

Both the 160 and 80M patterns look great – they are verticals with a decent low takeoff angle. I modeled the top of the two slanted wires connected and apart, and the models didn’t change much at all.

What is interesting about this exercise is that I could use the UrbanBeam support with two wires as guy’s and have 160 – 6M on one support. The only issue is then my TX antenna would be too close to my two RX antennas, and since they have preamps at the antenna and a second one in the shack – keeping the distance is critical. Right now my Inverted L is 70′ away from my nearest RX antenna, and I experience no issues (knock on wood).

Anyway, its always fun to think up new designs and model them.

 

 

Anticipating the SteppIR UrbanBeam Yagi

I’m hoping that my UrbanBeam will ship today – I’ve been told that it “should”. I’m reading the manual and would put it together as soon as I receive it – with hopes it could go up as soon as next weekend.

    

Dan, AC6LA has these animated EZnec plots on his web site, and this is what convinced me to serious consider this beam.

I’ve been building most of my Yagi’s and Moxon’s for years, but multi banding them always means suffering at least 1 dB gain – which means they end up being no better than an Extended Double Zepp gain wise. They do still have directionality, but at my QTH I never have a problem with close neighbors – even in the entire SF Bay Area. I am sure that those on the East Coast have it much worse as the population density of hams there is more than what we have on the West Coast.

My “Holy Grail” antenna wise has been to have only two antennas, one for the high bands and one for the low bands. Because my Inverted L works great on 160, 80 and 30M, and because the UrbanBeam (if it does live up to its specifications and Dan’s EZNec plots), this means I will be able to have 160 – 6M with 2 antennas.

The only crux with all of this is whether I will keep the 40M Phased Array up. My tests with the Cushcraft D40 (which is also a shortened 40M dipole like the UrbanBeam) shows that the phased array is better on the SP and the dipole better on the LP. This is very important, because we are on our way to the day where even 20M won’t be open.

I did have a SteppIR 2 element yagi way back in 2006 or so and it was a great antenna. I did find that not treating the fiberglass with a UV spray was a bad idea – after a couple years up, there was this white powder on the fiberglass tubes. I never had a problem with that antenna, and since then, I have worked with Arduino and Raspberry Pi with Stepper motors, and so I have warmed up to having moving parts in my antenna(s).

Its an expensive antenna, but because I am now pretty much retired from DXCC, I was able to sell my “backup” KX3 Line and use the proceeds for this antenna.

I have two Spiderbeam heavy duty aluminum push up masts, so I have plenty of “support power”. In fact, I even have an interesting idea for a “tubular tower” design that would more than double the strength of just having one. I’ll document that in my next blog.