40m Delta Loop

590px-Pythagoras_similar_triangles.svgThe rainy season runs from about November and sometime up to March, with peak cyclone activity at the height of summer, January and February. As a preventative measure, my next door neighbor trimmed one of the trees along our property line. I had some ropes in that tree to support a G5RV and when he gave me the heads up that crews would be whacking away at limbs, I thought it best to bring down the antenna. The G5RV never really hung high enough to work well and it stretched over the house, which may have added to noise, so I didn’t mind taking it down. Last week, I put up a new full wavelength 40m delta loop as a replacement.

I went with the delta loop because there is one large pine tree at the edge of the property and I was able to shoot a line over it with a wrist rocket. The lower corners are supported with guy lines from a telephone pole and another tree to each side of my house. The antenna is fed at the middle of the base, which is just at the edge of my roof, which makes it convenient to access. I had brought back a 50m roll of heavy duty green wire from Sotabeams in the UK. I have to remark that working with this very compliant wire was a pleasure after having made wire from household wire that loves to coil in the past.

By virtue of the position of supports, the antenna slopes from bottom to top towards the south, a bit more vertical than horizontal. Since I am feeding it from the bottom, the antenna polarization should be horizontal, but I believe that the sloping should add some directivity towards the North. I had considered feeding it up one side and using a quarter-wave of 75 ohm coax to transform the expected 100-ohm feed point impedance, but it would have been awkward to support a feedpoint at that position given what I had to work with.

I initially cut the antenna to a literal full wavelength, 299.8/7.1 * 1.05, where 1.05 was the fudge factor supplied in the ARRL antenna handbook. Initially, the resonant point was 6.9 Mhz, so I shortened the antenna in a few iterations, arriving at the intended 7.1 Mhz, where there was no reactive component and the resistive component was about 65 ohms — close enough to 50 for me to be happy to feed directly with 9913F7 coax and not worry about vSWR.

From the shack, the antenna works great with no tuner across 40m, but I don’t have a lot of experience at this point with regard to how the antenna performs. It is much louder on 40m than the hex beam, but most of the time that loudness is merely more noise thanks to the environment around the station.

DXPeditions: VK0EK and FT4JA

I am not an ardent DXer, but when an entity is only on the air every couple of decades, I’m willing to give it a try. Due to it’s remote location, Heard Island fits that description. Likewise, operation from Juan de Nova is not all that common, particularly as the Scattered Islands are the subject of a territorial dispute between Madagascar and France (and perhaps the Comoros would like a piece too).

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Immediate feedback from real time logging on the VK0EK website was very appreciated. I saw a CW contact recorded as HR8SV and was able to correct it on a subsequent attempt.

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The other side of the wall

Space_Shuttle_Columbia_launching

I got back from a trip on Friday, woke up at a reasonably leisurely hour on Saturday and thought it would be fun to test the waters of the big CW contest going on. Almost immediately, I was drawn in and didn’t leave the chair for another seven hours. Since the CQ WW DX contest is based on zones and there just aren’t many contesters in my zone (39), it was very flattering to be the object of desire for the rest of the world, but being on this side of the DX wall is quite different from what I’m used to.

At the best of times, I was working three calls a minute in a jedi mind-trance, but that of course was not typical. There were plenty of times where I was dialing around, trying to get noticed with my 100W and two-element antenna. However, the converse was also a challenge – sometimes I would be plugging away at a good rate and then all hell would break loose. Somewhere, someone had spotted me and suddenly I would find myself lying on the space shuttle launch pad, looking up at the main engines sparking to life, while trying to hear a song playing on someone’s ipod on the flight deck. The experience of operating into a solid wall of callers added some new perspectives…

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¡SSB en fuego!

This past weekend was the CQ WW SSB contest — one of the big ones. I usually have a vague idea about the approach of a contest and decide whether to take part on Friday of the contest weekend, but I had marked this one on the calendar ahead of time and was prepared. Aside from setting up everything and working a bit of SSB earlier in the week, I spent some time looking at propagation and figuring out where to point the antenna at different times of day to hit both areas with high densities of hams (NA, EU, Japan), but also beam heading that would cover the most DXCC entities, the multiplier for this contest.

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VHF Update: Repeaters, Earth and Sky

Relais 5R8ZZ
Relais 5R8ZZ

I got an email from Albert, 5R8GV, last week alerting me and other hams in the area that Serge, 5R8GX/FR5GX, had put a repeater into operation: 5R8ZZ.  The repeater is based at his house and puts out 16 watts (after filters) through a quarter-wave ground plane antenna on his roof. The repeater’s input frequency is 145.150 Mhz and the output frequency is 145.750 Mhz (i.e., set your radio to 145.750, with 600 khz negative offset). No PL tones are used; instead send a brief 1750 Hz tone to open the repeater.

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A quiet night at home

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A tale of low power operation in the dark.

For the past couple weeks, we’ve been experiencing load-shedding that starts about an hour after sunset.  The capital region of Madagascar does not have enough electrical power production capacity at present to run everything at once, so there is a rotating blackout. Now that I’ve added some UPSes, this has minimal impact on my family because we have a back-up generator that comes online in under a minute — usually. Last week, the generator didn’t start rumbling and we sat in the dark [presumably] looking at each other.

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5R8SV: The Hexbeam is Up

hexbeam_finally_upTL;DR? See the video on youtube.

My greatest limitation up to this point has been my antenna. For a few months, I worked QRP with the end-fed LNR 40/20/10, and it did a great job, although it wasn’t up very high. Putting up a G5RV allowed me to run 100W when my main shipment arrived, but the antenna was not ideal for my location – in particular, the twin-lead feed line, which is a radiating part of the antenna, came down low over the metal roof of my house and I had to tie it off to the side to keep it from detuning. Now, however, I have a “real” antenna up: the K4KIO hexbeam is mounted on heavy duty spiderbeam 10m mast, which sits atop a Yaesu G450 rotor.

It is effectively a two-element antenna on each band (6, 10, 12, 15, 17 and 20 meters), but each band is resonant and I do benefit from directivity, particularly in terms of noise reduction. I am hearing better from every direction, but particularly Asia. I’d write more in praise of the antenna, but I’m too eager to actually get on the air and use it…


I have been posting small interim updates on the station’s  QRZ site, and as they get stale, I’m moving them over to the blog for the record. Here are updates from last October through the beginning of this month:

June 21 2015: You know the drill — I had much more travel in April and May than I would have thought possible. The hexbeam? No, still not up. I’ve done a lot of metal work for the supports for the rotor and thrust bearing, but I won’t mount them until later this year. I’ll back back in the US from later this week (just in time for Field Day) through the beginning of August. I’ve updated all my online logs and sent an update to Phil, my QSL manager.

9 April 2015: I am in Madagascar for April except for the third week, when I’ll be in South Africa (so maybe you will hear a call from ZS/AI4SV at some point). I am trying to take advantage of the existing propagation while I can. I’ve had some contacts with VK/ZL in the last few days on 10m, including a few on voice. The highlight of my week, though, was tossing out a call on six meters and having a train of replies from around the Mediterranean: Italy, Malta, Jordan, Israel and several others. The K3 limits to about 70w using my G5RV antenna, which is certainly not ideal for 6m operation anyhow. I’ve been talking about putting up the hex beam for quite a while, hopefully I’ll get it done this month.

9 March 2015: I got back to Madagascar in time to spend a few hours on ARRL DX SSB and worked about thirty stations, including the Washington, BC, and the Northwest Territories, but with a predominance in New England. Alaska continues to elude me. I’ll be in Madagascar until the 14th and then away for the rest of the month. I did manage to get the post for the hexbeam anchored two meters deep in the backyard, so when I get back, that will be the first project.

24 February 2015: Thanks to everyone who worked me this past weekend during the ARRL DX CW contest. I hadn’t really planned to participate in it, but suddenly it was Saturday, I was home, and I had a working antenna, so there you go. I was very pleased to get 496 contacts including some states and provinces that I hadn’t previously reached. Work on the hexbeam continues in the background — I just slapped another coat of paint on the support post.

10 February 2015: The G5RV has worked out well, and I have contacts on 10, 12, 17, 20, 30, and 40 meters on it. Again, my limiting factor is local electrical noise, which is very variable. At some point I may try noise cancelation with a local sense antenna.

1 February 2015: I hung the G5RV today and discovered that it barely fits on the property. The matching section comes down over the house, so rather than let it hang straight down, I pulled it to the side and suspended it from a tree branch to keep it away from the metal roof. I can only imagine what this does to the radiation pattern. I swept the antenna with an analyzer, and get < 3:1 on 80, 40, 20, 17, and 10 meters. I get high SWR on 30m, so I don’t expect to run that band, and I’ll have to see how the built-in tuner in the K3 does on the other bands. I hopped on 17m earlier this evening running 100W for the first time for this station. I ran 100+ contacts, so at least I know it is not a dummy load. I am hoping to try out the other bands after work in the coming week.

From my trip to the US last week, I did bring back the hex beam mast, so that longer term project can now move ahead as well. I also picked up a powergate, which provides battery backup. We have intermittent power losses and even if backup power comes on line, I found it awkward to be mid-QSO and lose power. If I was operating split, the K3 would forget the set up and I’d need to reprogram. Now, the radio switches seamlessly to battery until main power is restored. Finally, the TS-450SAT is now set up for digital operation. I had a couple PSK31 contacts last night and will try some more digimodes as time permits.

18 January 2014: In the US for a week of meetings: a couple days in Seattle and a couple in Washington, DC. I should be back in Madagascar at the very end of January. Barring any complications getting the spiderbeam mast through as luggage (Air France says it’s okay in terms of dimensions as a “second bag”), I’ll get to work on raising the hex beam, but this will entail digging a big hole, finding a suitable post, anchoring in concrete, etc. – I’ll get it up as soon as I can if weather cooperates. Meanwhile, I’ll try to put the G5RV in place. I’m also hoping to get a digimode radio on the air in February, so maybe you’ll soon hear strange sounds eminating from the Red Island.

29 December 2014:  It has been a little more difficult to get things set up than anticipated for two reasons: 1) worked related travel; and 2) rainy season. It only rains a couple hours on certain days, but when it rains, it comes down hard. I had anticipated making a workshop in the garage, but the floor floods briefly when the rain pounds down. Consequently, project #1 has become raised flooring and shelving in the garage. While that will be an ongoing project for the next month, I’ve started setting up the shack indoors and have created an access route to bring feedlines into the shack. I have brought the coax from the LNR end-fed antenna into the shack and it is now hooked up to the K3. The antenna only handles 25W, but that’s 5x more than what I had before, so at least I am heading in the right direction.

26 November 2014: The station gear finally arrived last week. Due to work, I’ve just started unpacking it all. Now that I have tools and materials, I can start wiring up the house as needed. This is probably going to take a while since I’ll be away on business (and vacation) for much of December. When possible, I’ll continue to operate from the porch, perhaps with a bit more power using the K3. However, now that rainy season is upon us, it’s trickier to operate from that location. I’m hoping to upload everything to date to LOTW this week.

19 Oct 2014: A bit less activity in the last week or so due to business and travel, but still accruing the new DXCC entities as time permits. Some highlights include working my QSL manager G3SWH, Phil, a mobile station in Germany, DF4TD/M and a few stations in the Oceania DX contest. No change in equpment: the main station gear is still on the way, probably delayed a couple weeks by the Air France strike at the end of September. I’ve had some discussions with a local engineering company about putting up a “pylône de télécommunications” to support the hexbeam and G450A rotor, so that project is also cooking in the background.

Solder Fan

IMG_20150528_144840 IMG_20150529_201936 IMG_20150529_201958 IMG_20150529_202007This project arose from a sudden desire to stop inhaling solder smoke. I just got back from about three weeks of constant travel around Africa with a bad head cold, cough and sore throat. After being away, I was itching to solder up something, but didn’t want to push myself any closer to bronchitis. The solution: a fan to waft away the solder smoke.

I had a bunch of waffle fans removed from computers, but some of them proved very wimpy. One in particular was super-quiet and drew about 200 mA, but was barely able to move air. Since more is always better, I dug into the junque box and pulled out a bunch of fans that I have removed from a commercial server. They were small, but powerful. Alone, each drew about a half amp and when plugged in a 12V battery (or tapped into the bench’s 12V supply), would vibrate themselves around the table. If one fan is good… four is even better.

I created a wood frame with some channels made from angle aluminum. Since the metal impeller blades are like little razors, I stapled metal mesh over both sides. After assembling the whole thing, it occurred to me that all the fans should face the same direction. Luckily, the wood glue hadn’t set by that point, and I was able to disassemble part of the frame, flip around a couple fans, and screw the whole thing back together.

With four fans running full speed, this thing is loud and produces almost enough thrust to take off. So, the interesting part of this project is not the fan itself, but the fan controller. Any sort of rheostat or linear device that would ramp up or down the drive voltage would be very inefficient and produce a lot of waste heat, so I went with a variable pulse width modulator. Rather than reinvent the wheel, I used a design described on the PC Silencio website. Two sections of the quad op amp create a triangle wave, another serves as buffer for a voltage divider, and the final section serves as a comparator to slice off the triangle wave at the level set by the voltage divider. The threshold determines the duty cycle of the generated square wave, which drives the motor at full voltage.

I didn’t have a LM324 in DIP14 layout, so I substituted a TLC271 op amp, which worked fine. For the n-channel MOSFET driving the motors, I went with an STP16NF06 (my old standby, used in previous projects such as the TEAPOT and Texas Topper Amplifier). Regardless of setting, the mosfet remains cool since it’s essentially either on or off and not hanging out in the linear range at all.

In practice, running the fans at near the lowest setting works fine for pulling away smoke from routine soldering. Since the question will inevitably arise — I should mention that in order to solder together the fan, I used a breadboarded version of the PWM circuit to run the fans so I could solder them together — thus getting around this bootstrapping issue.

2015 ARRL CW DX

nodakotas
If North America were a toroid, one could pass the windings through the Dakotas.

Having recently put up the G5RV, I gave the ARRL DX CW contest a shot this past weekend. The antenna is up only about 10m and is not resonant on 15m, but it has performed well on 10 and 20m in the past. On the first night, 10m was very quiet, but activity on 20m was brisk, particularly in the early morning hours when I was working two calls per minute.

In principle, 10m should have been open starting the in mid-afternoon on Sunday, but it was slow until around dinner time. Again, 20m was my main band, despite having mostly mined it out the previous day. I managed to get a few contacts on 15m, and even fewer on 40m, where local noise was a problem.

I didn’t stay in the chair the full time, even when I had favorable North American windows. I had to disconnect the antenna for some time due to thunderstorms on Saturday afternoon and on Sunday evening I had a guest in town and went out for dinner. Still, I am happy with the number of contacts I made given my conditions.

I worked a few states that I hadn’t such as Vermont, Rhode Island, Delaware, West Virginia, Nevada and Wyoming — hopefully, those stations will QSL via LOTW. I heard a North Dakota station, but barely, and he was drowning in a pile up. Maybe I’ll take another shot when Sweepstakes or some other convenient contest rolls around and I have the hexbeam up.

My final tally:

Band QSOs Mults
40m 7 4
20m 418 52
15m 18 13
10m 56 26

More Garage

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Water in the garage. This is a problem.

In the previous post, I mentioned that our shipment from the US came in several large wood crates, just as the rainy season started. I had a lot of boxes of radio gear, tools, and other items that needed sorting and I wanted to work in the garage, but since the garage is built below ground at the end of a down-sloping driveway, I was worried that the garage floor could not be trusted to remain dry. As the rainy season picked up, I soon found that this concern was justified, as the french drain in front of the garage could not cope with the run-off.

I had a few of the bottom pallets from the shipping crate; each sits about 8 cm above the floor on wood blocks. I moved these to the back of the garage (since the floor slopes towards the front where the drain is) and piled everything on top of them, while I considered my options.

Although it is rainy season, most of the time it is not actually raining. Most of the water in the front of the garage would run out almost immediately, and the floor would often be dry a half hour later. Unfortunately, the receding water would always leave behind a fine red mud, or after drying, dust.

Making some sort of raised flooring seemed like a good idea. Unfortunately, the plywood used in shipping crates is of very poor quality and only about a cm thick. I could walk on it, but it would groan and sag. However, I had a lot of it.

Fine, government-quality plywood.
Fine, government-quality plywood.

I spent the next couple weeks disassembling all of the crates, pulling out the useful two-by lumber. I must have pulled out thousands of nails — most of which I was able to straighten and use again. I remember the day I packed out in Virginia: it was also raining. The moving guys covered the crates in copious amounts of plastic wrap. The corollary is that both the framing lumber and the plywood were chock full of staples. I painstakingly yanked them all because I was paranoid that I might hit them with an electric saw later in this process.

I piled up the lumber, trimmed off bits that were too damaged to be useful, and played a constant game of shifting around unpacked boxes, lumber and tools, to get at the materials I needed while still keeping everything high and dry.

Since the plywood was so thin, I added some reinforcing cross members to the lumber framing and then tossed another layer of plywood on top, laminating it to the existing plywood with some locally purchased wood glue. Between the wood glue and additional nails, the double-thickness plywood made a solid floor. Still a little creaky, but no real give.

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Two of the pallets support a table on the left and a pile of bricks on the right. Note the red stain on the floor, where water had accumulated transiently.

The water never got more than a centimeter or so high in the garage, but I didn’t like the idea of wood blocks sitting in water. This set up has to last four years or so.  I needed some kind of solid, water-resistant material to serve as supports for the wooden feet below the platforms. Not surprisingly, I obtained locally produced bricks. Bricks are very common here — they are produced from rice paddy mud between crops. They are not the best quality bricks as they lack binding materials and fiber; they are just baked mud. They are relatively fragile to shocks, but resilient to compressive force. For my application, they worked fine, and the price is right: 80 ariary each (about three cents a piece).

So, in boosted the existing flooring up, with two bricks under each supporting wood block, and then fabricated some additional flooring so I had covered the rectangular middle portion of the garage. The back of the garage is strangely trapezoidal, so I put that off for a bit.

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A view from the back of the garage looking towards the door (which is down).

I needed a place to work and also some storage, so I made some work benches. I more or less followed a design from a YouTube video for a bench that looked very solid. I already had an Ikea table, which works best at a sitting height, so I made the benches to be used while standing. Like the floors, the benches are made out of wood recovered from the packing crates (although I did top one with some nicer, sanded plywood that I had shipped for that purpose).

Going back to the source of the problem, drainage, I had some workers clean out the drain area at the left end of the grill, above. I hadn’t realized how much silt had collected. They reamed out the pipe downstream as well. I watched the drain during the next heavy storm and was pleased that it had no problem diverting the water as fast as it came.

With less worry about moisture, I decided to install a short carpet in the central area of the garage. The addition of the carpet made it feel much more comfortable. Next came the rolling office chair.

Finally - some storage. All those tiny parts!
Finally – some storage. All those tiny parts!

Finally, I set up the Ikea shelfing and was able to unpack the many boxes of hoarded electronic bits and pieces. I still have some unpacking to do, but I am now able to get to everything: patch cords, adapters, tools, etc., which will let me get going on station and antenna set up.

The first project for the new workspace: construction of an antenna panel to bring coax into the shack through lightning arrestors and antenna switches. Other projects on a near infinite list include finishing the back portion of the garage and installing some storage shelves for larger items, working on the mount for the hex beam antenna, and fabricating some additional antennas.