How to Build a Crappie Moxon

September 1, 2014

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The first thing you need is a hub. I use a DX Engineering Boom to Mast Plate, part number BMP-2B. I also use a floor flange that you can get at any hardware store, plus the screw in threaded pipe. I let mine “rust weld”, but some come with a set screw – where the threaded pipe can be set. Four holes have to be drilled right at the center of the plate – so you will have a balanced and very sturdy hub. I fit the threaded pipe into a section of miltary mast – that is bolted, and which goes inside a Yaesu G450 rotator. This is over kill, but very sturdy. Everything I make is pretty heavy duty.

The hub will need only 4 more holes drilled – to accomodate the 4 spreaders and single center support. More on this later.

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I use 3′ aluminum tubing as “sleeves” that go into the spreaders. The spreaders are Cabellas Crappie (fishing) poles – the 16.5′ models. The outside diameter of the aluminum sleeves must fit snuggly into the fiberglass Crappie poles. The aluminum spreaders are bolted by the bolts that go into the floor flange underneath the DXE boom to mast plate. U-Bolts hold each element in place. I then put the center support on top – it is made of two much shorter Crappie poles. The way to shorten the Crappie poles is to just slide the sections at the tip out – one by one. NEVER use the really thin tip that comes with these. If you ever needed to extend the spreaders – you could use longer aluminum sleeves, or use a Jackite Kite Pole instead of these fishing rods. HOWEVER – a Jackite based Moxon would be much stronger, heavier and require a much bigger boom to mast plate for your hub. I like the Crappie poles better.

The angle of the spreaders is 140 degrees out away from the plate – which forces a rectangle that will accomodate the size of the Moxon wires. The wires are calculated using the Moxgen program (Google Moxgen for a bunch or great links):

moxgen

You can even Google “triangle calculator” and you will find one that handles right angle calculations – and where you can get the exact angle at which the spreaders need to leave the hub. I am not too picky – since the spreaders can be curved to fit the dimensions of the rectangle – just make sure the spreaders make a rectangle where the “A” and “E” dimensions can be accomodated.

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Here are the spreaders – the Cabellas Crappie Poles. I spray all fiberglass poles with “Plastidip” – because it covers the fiberglass and protects it from UV Rays. Years ago, I had a 2 Element SteppIR, and after one or two years – the fiberglass tubes were toast. That was a very expensive lesson to learn.

In this case, I am just trying to avoid what happens to fiberglass after only a year – where it is untreated – it first turns powder white, and then the second year – starts cracking and splitting. Can you imagine the work it would take to replace all of the fiberglass on a giant SteppIR antenna? This Moxon only costs about $100 to build – but of course its only a 2 element mono band antenna. It is possible to easily duo band this antenna – more on that later.

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I use masons twine to adjust the ends of the spreaders to accomodate the wire that I will add. Here is a close up view of the twine on the end:

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Now its time for building the wire elements. I use #14 AWG “FlexWeave” wire. I cut some of the discarded fiberglass left ove from removing the tops from the spreaders, and drill holes to ensure that the gap at each end of the Moxon is perfect. This is the only really critical part of this antenna:

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I use ring terminals on each end of the wire – they are crimped and soldered. Remember that adding the ring lugs can change the length of the wire elements – so measure from the center of the hole of each ring when cutting the wire – else you will be lower in frequency than you had expected – since its easy to accidentally add length by adding rings.

The gap insulator – as you can see above, uses nylon bolts and nuts – and once secured, I coat both ends of the bolt with glue from a hot glue gun. This will prevent the nylon bolts from ever coming lose. Also note that the fiberglass tube cut for the gap is wrapped with electrical tape. This is a lot more convenient than spraying with plastidip, and I also let a little tape overhang and tuck it into the ends of the fiberglass – to prevent splitting or cracking. Make sure your cuts and drilling are very “clean”. I drill at least 1/2 in from the end – so that there is no splitting – which could let the wire pull out over time. Because I use these ends in a situation where they are pulled tight – to retain the geometry of the rectangle, these gap insulators have to be very strong. The fiberglass keeps them light weight – which is also a prerequisite – so they won’t droop down.

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This is how I affix the wire to the poles – I use two wire ties, then electrical tape to tape the wire in and around those two wire ties.

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I use a 1:1 current choke at the feedpoint, rated at 5 KW – so I can run full power. Thi smay look “hokey”, but I use 4 wire ties and then electrical tape. When my LMR-400 feedline is connected and taped to the boom – it acts as a final “anchor”. This works very well. The driver wire element also is pulled taught – so the choke won’t move at all.

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I’ve run a few tests using the Reverse Beacon Network (RBN), and the Moxon at 30′ does seem to beat the 3L 20M Yagi – up 45′ – but used as a rotatable dipole, by between 3 – 6 dB which certainly is in the right range, and agrees with what HFTA said it would. I need to do more testing – and will report on what I find in a subsequent posting.

 

 

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My lowband vertical antenna was a Cushcraft MA160V, and at 36′ – its efficiency at best (even with 100 radials) was maybe 40%. Which means with 1000 watts, 400 watts would be radiated.

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On page 9-46 of the ON4UN Lowband DX-ing book – my ground resistance is in the area of 5 ohms – so my efficiency – with 100 radials would be 72%. On top of that – I added a top hat with a surface area of 33′ and had increased the radiating portion of the vertical from 10 meters to 15 meters. So – lets round down to 70% – the effect would be like adding 300 watts, or 30% better performance. Quite significant – and worth the effort for sure!

 

Navassa, KP1

August 30, 2014

navassa-chart2

Navassa is rated #1 Most Wanted by Clublog, and we now know it will be activated in the next 18 months.

Since it generally takes a year to plan for a DX-pedition, and because the US F&W will accept applications from several competing groups, we know that 18 months out is February 2016 – and that the activation will be that late or sooner.

When I re-visit the K5D web site, I see that the KP1-5 group had won the application and permit for Desecheo, and they activated KP5 in February. I can only imagine that activating a Caribbean island would be nicest weather wise after hurricane season – which ends in November, and before it gets too hot. This means December – March or so.

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I’m going to guess that KP1 will be activated between December 2015 and February 2016. This means it will land right around the same time as Heard Island – VK0EK  and who knows – maybe other Top 10 entities – E3 and a few other possibilities come to mind. In any case – I will bet that late 2015 and early 2016 will have several very exciting major Top 10 DX-peditions activating. Who knows – I might even be able to snag 3 or 4 ATNO’s before the end of 2016. Maybe I will only end up needing 3 or 4 for DXCC Honor Roll #1 when 2016 is all done and over with. This is a very new and exciting surprise possibility. I expected it to take a LOT longer.

Propagation for Heard Island will be “good enough”, with 40, 30, 20 and 17M being the bands with the highest probability for West Coasters.

As far as KP1 is concerned, here is what the K6TU propagation service predicts – using my own antenna.13 file:

kp1_na

This means – while EU will command FT4TA, NA will command KP1. There is a band open 24×7 to all of the US, and plenty of hours where only NA and SA are favored. For the West Coast, there isn’t a time or band where it favors just the West Coast, but I would expect that after the East Coast and Central US dominate the pileups – then the West Coast will get its chance. There might even be a few bands where the longer skip does favor the West Coast over the East and Central, but it really doesn’t matter.

And here is what my 3L 20M yagi will do:

ky6r_kp1_hfta

ALL of the other bands will have pretty much the same pattern – I can clear the hills in that direction – which is about 100 degrees. No polar path, no worries about competition from EU, basically it should be just like K5D and HK0NA – in other words – as long as the team that gets selected – and they are the best of the best – it will be a cake walk for NA.

This one will be super exciting and fun.

Why DXCC Honor Roll #1?

August 30, 2014

DXCC Top of Honor Roll

The DXCC program has an almost mystical quality to it. One of the funniest things I have seen are how several people on the eHam DX Forum proclaim “I don’t care about awards chasing” – but even so – they like to “kibbitz” about the DXCC List.

In fact, during the Summer DX Doldrums – or when we are at the bottom of a cycle, or when there just aren’t any announced or planned “juicy and rare” DX-peditions on the calendar, the eHam DX Forum is quite active.

I never see anyone carry on talking about IOTA or the CQ Awards anywhere near like the ARRL DXCC Program. Its almost got a “religious” quality to it.

Cass, WA6AUD (SK) wrote extensively about it, and the NCDXC has posted most of his old articles:

http://ncdxc.org/pages/wcdxb.html

They are really superb – and timely even today, because they always catch me getting all excited or “riled up” over something trivial. After all – DXCC awards chasing is a trivial pursuit, but for me – has acted as a great diversion when I am bored to death at work – or when I went through other rough spots in life.

But the #1 reason why the DXCC program works for me is that it forces me to get my station and operating skills up to snuff. This is not an easy award to achieve. Regular mixed Honor Roll seemed “daunting” – and I was in a really bad shape as of Decmeber 2011. I was pig headed and thought my wimpy 20M Moxon up 30′ 200 watts and a couple dipoles would get me there – after all, these antennas got me to 8BDXCC and 1500 Challenge – so I thought I had it nailed. Turns out – HFTA got me straightened out, over the technical hump, and I worked the last 7 I needed in 2012. I have never seen such a clear “call and response” in DX-ing where I seemed to go from “98 pound weakling” to “Charles Atlas” over night. HFTA made it so no one could kick sand in my DX face . . .  Confidence is everything in DX-ing!

DXCC Honor Roll #1 takes it to the next level. There IS competition – but only in the pileups. You know when your station works really well – and that then gives you confidence. Once you have confidence, there is nothing holding you back, and you WILL get that ATNO.

Of course – as long as you can first HEAR them!

Anyway, I like climbing the DX Ladders and DXCC Online List. I’m way down below the guys at the top – but in a short amount of time, I have steadily climbed the ladder – and so this reminds me of when I ran track or cross country. I always wanted just a little better time  – or a little more height (I was a pole vaulter – probably the shortest in Sussex County) – but I at least placed every track meet – mostly third place – and I only did it one season because my High School had 92 Seniors and not enough people to make a full track team – so I signed up not knowing any better. Newton, NJ was the County seat in one of the biggest counties in tiny NJ, and the Appalachian Trail ran almost through it. I was a big fish in a small pond – Newton’s population was 7000, but I thought I could do anything I put my mind to. Ham Radio at age 13 in 1973 really cemented my path to my career in high tech.

I can’t make up for all those years I was off the air (1977 – 2001), and there are many I will never come close to with my “score”, but thats my fault – those who stayed active all those years worked the entities that I still need. That’s just the way it goes – you just do your best, and there never has nor ever will be a “level playing field”. No technology will trump perserverence or persistence. You were either on the air to work K5K – or like me – you weren’t. Tough cookies. Its more than that movie “Being There” – because you have to “Be There”, but well prepared and “present”.

Hear them – then have the gain required to get through what seems like the ever growing and raucous pileups. Adding power on top of a great antenna system is the right order – because an amplifier won’t let you hear the DX any better than before! This is the strategy that has worked for me every time – and strategizing while waiting for that next ATNO is big fun. Goofing around in the shack or out in the back yard is a pure relaxing joy for me – and I am always learning – which is what the DXCC program forces you to do.

I am so ready for any of the last 8 I need – so bring it!

Huge DX Announcement Day!

August 30, 2014

KY6R_14_AZ_Needed_30M

Its hard to believe, but half of what I need for Honor Roll #1 is “in the works”:

VK0/H – Heard Island

KP1 – Navassa

FT/T – Tromelin

E3 – Eritrea

Who knows – maybe there are even more waiting in the wings? Today – E3 and KP1 were announced – for me – that is HUGE – and changes everything. Maybe I will make it to Honor Roll #1 a lot sooner than I expected.

One can only hope!

And I have nailed it as far as working on my antenna systems and power moving forward.

Now this is what the DX game is all about – heh heh.

Why Full Power is Good!

August 29, 2014

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Full power forces you to make sure that everything in the chain between the exciter and the antenna are working 100%. No bad solder connections, no wimpy under powered chokes or baluns, no antenna tuners that are not up to the task. This is especially true on 160M – trying to get full power on Top Band will really “test your mettle”, especially with the shortened antennas that most of us are forced to build. As you go up in the bands and you can put up 1/4 w.l verticals or full sized yagis – that do not have traps or other coils and whatnot – then the situation gets a lot better.

The circuit for my 160/80M vertical is from page 9-42 from the ON4UN Low Band DX-ing Book – but modified for the exact components and values that I used, as well as the height dimensions:

ky6r_match

What is especially nice is that I can tune this circuit for 160M and 80M and bypass the Palstar AT2K – which – like most tuners – might have a problem with the high voltages associated with the feedpoint of a shortened hatted vertical. The key was to BYPASS the AT2K – because it had arc’ed on the lowbands before with its components switched in. My KAT-500 with the KPA-500 did a better job – but that’s because the KAT-500 is a switched L circuit – not a T circuit. But a BIG part of this is that at 500 watts and below – the voltages are a lot lower than at 1500 watts – so its not the Palstar AT2K’s fault – its the severe compromise I am making with a shortened antenna.

BTW – I did work FT5ZM on 160 and 80M with a “lesser” and less efficient version of this antenna – an MA160V that just had extra aluminum added to it and a series capacitor to tune at the feedpoint. I feel I have improved things with the new capaciitance hat that is 33′ in circumference, and the smaller, more efficient coil doing the loading at the top of the antenna.

I would much rather handle the match at the top and base of my shortened vertical anyway – it just seems like the best place to handle the load – it just seems a lot more efficient than trying to tune in the shack with an antenna tuner.

Phil, AD5X has a great QST article on a base matching circuit that can switch between 160, 80 and all higher bands – and I might build his circuit. Or – I might just create a second set of components that I have now – and have two LC circuits and then use a high voltage relay to switch between one or the other. I have a Jennings RB2A and a regular DPDT relay laying around. Another idea is to use a vacuum variable capacitor with a motor and maybe even a motor on a very high power variable inductor that I have. In the meantime – its easy enough to go out back and tune it for either 160M or 80M – typically I am on 160M as I don’t really care for 80M anyway. But – if an ATNO is on 80M – like FT4TA – you better believe I will be out there the afternoon before doing a quick tune to one or the other.

I expect an upgraded “in the shack” remote automated circuit to happen before FT4TA – hi hi. All home brewed – because that’s how I like doing it.

I will do some more research, but it seems that I can come up with a tuned circuit and switching arrangement than can handle the power on 160M and 80M and just switch between 160 and 80M.

The resonant frequency of the vertical – with no components in line – is 3.1 mhz – so it “splits the difference”.

My antennas on 30, 40, 20 and 15M are also either at resonance and don’t require a tuner – or require so little from the tuner that it doesn’t matter. I’ve become a resonant mono band “junkie” of late. Just makes too much sense to me. At lower powers its easy to get “sloppy” and just use a tuner in line – as I did with the KPA-500 and KAT-500. I feel I am forced to make my antennas more efrficient than they were before. The fewer components in line, the better. But on 160 and 80M – its unavoidable when you have such a short antenna.

And the fact that 160, 80, 30, 40, 20 and 15M can handle full power is the real test of my antenna system. I’m now there – and loving it. No faults, arc’s or sparks!

 

 

FT4TA and KY6R on 15M

August 29, 2014

ft4ta_ky6r_15M

After assembling the homebrewed 15M yagi, I realized that it would overlap underneath the 3L 20M yagi more than I would have liked – and could cause some negative interaction. It also was heavier and might be a bit too big for the support mast that I have.

I was wondering if just using my 3L 20M yagi as a rotatable dipole on 17 – 10M would be “good enough”. Its not – see the blue line. However, a lightweight wire Moxon could be a great solution (red line). The 3L yagi would be 1.5 dB better than the Moxon, and the Moxon is 2 dB better than the rotatable dipole idea. So its a great compromise.

ft4ta_k6tu

15 meters is a good band to add a monobander to – because we are still in the same year as the peak of Cycle 24. When VK0EK goes to Heard Island, 17M will be the better of the two bands to put something up – and I will no doubt swap the 15M Moxon for a 17M Moxon next year.

I tweaked the tuning on my 160M short hatted vertical and can now run legal limit on it, but I will still probably keep it down to about 1KW just to be safe. On 160M – when you have a short hatted and loaded vertical – the voltages are so high that all kinds of weird arcing can happen – so its better to play it safe.

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So, with this 15M Moxon, I will have mono banders on 160, 40, 20 and 15, and can run legal limit on those bands. I can run 200 watts easily on 30M with the tuner, and will be able to use either the yagi or the Moxon on 17M with a tuner. I am not going to worry about 80, 12 or 10M so much, but with a tuner can also use those bands if necessary.

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