Tropical Cyclone Enawo

This storm is already intense and predicted to hit the north-east side of the island tomorrow morning with hurricane force. For the last three years, we have been lucky with storms tracking to one side or the other of the QTH, but the track for this one cuts straight down the center of the island and should pass near the capital city, Antananarivo. The prediction has been consistent and is now close enough to be sure that we will experience some rough weather in the next few days.

To that end, for the first time, I have lowered the hex beam antenna. I collapsed down the telescoping sections of the heavy duty 10m spiderbeam mast and threw some additional guy lines over the central plate to which the arms attach. The wooden support beam goes two meters into the ground and is surrounded by buried concrete, so I am not worried about the base, but I do expect the fiberglass arms to be battered about. I considered dismounting the whole antenna, but that would have required more manpower than I have readily available, so it will have to ride out the storm.

Continue reading “Tropical Cyclone Enawo”

Internet backup power

About the time I am wrapping up in the office, the sun has risen and people are getting into work on the East Coast of the United States. I leave early enough to get home so I can make teleconferences that start at 9 Eastern. I’d have quite a phone bill if I dialed direct, but fortunately, I can make most of these calls over the internet. Although Madagascar is a developing country, we have fiber to the house. The upstream connection isn’t entirely stable, but it is up most of the time, and throughput is surprisingly high. However, I still run into problems when the power blinks off.

The ISP has adequate backup power to maintain the connection, at least for some time, so this is my problem in the house. The house too has a backup generator, but there’s a couple seconds to shift over from mains to generator and vice versa. In that time, the houses’s router goes down and takes a minute or so to reboot every time power switches over. What’s needed is a UPS, but the smallest computer UPS here runs around $150. Also, it seems like a UPS is massive overkill when the problem is just to keep a router happy for about a minute.

I have a good stash of small lead acid batteries for portable ham radio use, and it occurred to me that I could probably use a couple in backup power supply projects. At this point, I’ve come up with two designs built of materials squirreled away in my garage. Schematics are below the cut for anyone interested. Continue reading “Internet backup power”

Visit to Zambia

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Flooding in Madagacar after the most recent cyclone.

This year’s cyclone season has been unusually severe – folks in Madagascar are telling me that it is the worst one since around 1959, particularly from the perspective of the central highlands. However, most of the precipitation has been on the coasts, where towns are literally underwater. Storm systems tend to form over Mozambique, intensify in crossing the channel, land forcefully on the west coast of the island, cut across it, and continue into the Indian ocean, either eastwards towards Réunion or shifting towards the south. Along the way, the storms dumped enough rain to entirely saturate the soil in the first month or two. Now, there is nowhere for the water to go, and it is overflowing dikes, bursting dams, and causing mudslides. Before the rainy season, the government was struggling to keep the wobbly national infrastructure working, but at this point, it is struggling to maintain basic services such as electricity and road maintenance. Continue reading “Visit to Zambia”

The G5RV is up

G5RVF4The antenna situation has improved. There is progress on the hex beam, but in the meantime I’ve put up a G5RV. It is almost exactly the size of the largest run possible on my property. I had some difficulty getting enough angle on the trees to shoot the line and I am frankly surprised it all worked. The line is tied down to the tree trunk on one end, and the other loops over a tree, then through a metal loop screwed into the property wall, and that end suspends a brick, which maintains tension on the line but has enough give to allow tree motion. The center twin lead is centered over my house and I was not able to get the two arms of the antenna high enough to allow the feed line to hang down straight; this is not ideal as it will change the plane of radiation since the feed line is active in this design. I was also concerned about the feed line coming down too close to the metal roof, so I have arranged another support for the feed line, which pulls it close to horizontal. It also keeps it away from the high power security lights that rim the roof and which put out some RF.

I swept the antenna with an MFJ analyzer in the shack and the SWR is less than 3:1 on 80, 40, 20, 17 and 10m. I have had some good runs on 10, 17, and 20 meters, and a few contacts on 40m. Even on bands where it it not resonant, I’ve had reasonable success using a tuner; being able to run 100W gives me some margin for inefficiency. I worked one EU station after another one afternoon on 30m, and finally had a contact with Alain, 5R8AL, also in Madagascar on 12m. The additional power has allowed me to run a frequency on voice.  I’ve now set up the TS450 for digital communications and have had a few PSK31 contacts as well. I’ve getting some RF back, which is affecting the external USB sound card, so a near term project will be fixing station grounding.

wood mill workers milling the tree into a postAs for the hex beam, I finally have all materials. I visited a local lumber yard and had a 4m x 15cm x 15cm post milled. It arrived at my house on a cart and is now sitting across two chairs on my porch. I’ve given the post a coat of wood treatment (permethrin + cobalt salts) and will paint it for more protection. Meanwhile, an almost 2m deep hole has been dug in the backyard, and I’ve purchased about 200 kg of cement, which with some aggregate will become the base for the wooden support beam.

The plan is to get the base in place and set up a shelf using angle iron to support the G450 rotor. Further up the post, I will install a universal thrust bearing to handle the lateral load. A 10m spiderbeam telescoping mast will support the hex beam, and will itself be guyed at two levels. Finishing this project will await some good weather and enough time to see it through.

First Big Storm

Friday afternoon, a “moderate tropical cyclone” swept west-to-east across the Island. It was a big enough storm to get a name, Chezda, and I’d been watching it on satellite pictures for a couple days. In the last afternoon, it hit the west coast, bringing rain and wind. This is what it looked like. It’s the swirly cotton thing on the left. The more ominous looking storm on the right is another one, Bansi, that wasn’t a problem for Madagascar, but did affect Ile Rodriques. It is headed southeast, so not so much of a concern.

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Since the picture was taken, the center of Chezda has moved off the east coast of Madagascar, but not before dumping a lot of water yesterday and blowing fiercely overnight. Many low-lying areas were flooded. We’re a couple weeks into the rice harvesting season, and in this area, it looked like only about half the rice had been harvested, so I would guess some crops might have been lost to inundation.

There were a lot of power fluctuations yesterday, but as far as I can tell, no major damage in the local area. The wind died down the the sun came out around ten this morning. I’m pleased to report that aside from a bit of water around the garage door, no water entered the garage. The improvements to drainage happened just in time.

The storm is predicted to continue to move south-east and should miss the populated islands in our region.

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