AI4SV/3 QRV

So, I should explain why a crucifix appears to be hovering about thirty feet above my house.

My new HF antenna hovers above the house.

When I got back to the US, I had a hard time figuring out how to put up an antenna at the house that I’m renting in Maryland, just north of Washington, DC. The house is surrounded on three sides by power lines and there’s only one tall tree. After much consideration and with the help of a neighbor’s tree, I finally managed to put a dipole in place just before Christmas.

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5R8SV Satellite Ops

After I took the hexbeam down, sanded it, painted it and packed it away, I still had a G450 rotor on my hands, so I thought I would try my hand at satellite operation. Over last weekend, I literally lashed together a satellite station — the rotor platform is held to the roof with taut line hitches.

Our house isn’t ideally situated for satellite operation — particularly to the south where some tall pine trees blot out the sky, but in the other directions, the antenna can see down to about ten or fifteen degrees above the horizon.

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Thanks, Eliakim

Morning antenna maintenance involved an N95 particulate mask, gloves, and goggles today.

I arrived back in Madagascar late in the evening last week after a brief vacation in Réunion. The next morning, I fired up the rig to see what was going on in the CQ WW WPX SSB contest and rotated the hexbeam towards Japan. The rotor control showed movement through about the first ten degrees, and then it froze. I backed off, tried jiggering it back and forth a bit, thinking that perhaps it was just sticking, but gave up after a few seconds because I didn’t want to strain the motor. I walked out back…

… And it was clear why the antenna wasn’t rotating, about a meter and half below the base of the hex beam, the mast had a kink of about 20 degrees, and the hexbeam was lopsided, brushing against a nearby tree. After surviving four cyclone seasons, it appears that the last one of this season, Eliakim, took its toll.

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Repairing the 40/20/10 EFHW antenna

The repaired antenna; details below.

My LNR precision trail-friendly end-fed halfwave antenna has been my go to antenna for SOTA and other field operations for several years. It is compact, easy to deploy in a tree or on a telescoping mast, and it gets good signal reports. Unfortunately, after many years of use and substantial abuse, the antenna broke on my last trip. When I got back, I put it back together, almost good as new.

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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.

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SOTA: ZS/WC-043 Maclear’s Beacon

Over the last two weeks, I have traveled in South Africa and Botswana, primarily on business, but with a little time set aside for radio fun. Unfortunately, I didn’t receive regulatory clearance to operate in Botswana in time for the trip, so I left the radio in my suitcase there (despite the bilateral agreement on amateur radio between the US and Botswana, to operate, US hams need to file with BOCRA, which takes some time). However, in South Africa, I operated from Pretoria and Cape Town, visited a local ham club, and activated a SOTA peak.

While I would prefer to activate less common SOTA peaks, when traveling I often need to consider what is in range of public transportation. Table Mountain is a 50 Rand ride on Uber from downtown Cape Town and is also a stop on some hop-on/hop-off bus tours. Two hanging cable cars run from the base of the mountain to its top. There is a long path up as well, but as I was lugging more equipment than usual, I decided to take the cable car, which was something like 250 Rand round trip (about $20; pricey, but it is, after all, a tourist attraction).

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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.

Wifi for the Garage

A look inside the Linksys WRT54GS router used in this project.
A look inside the Linksys WRT54GS router used in this project.

Propagation has been abysmal, so it’s time to hang out in garage and work on projects. One catch: the garage PC gave up the ghost about a month ago. The Windows 7 computer had been functioning for a few months as a wifi repeater that let me use other wireless devices in the garage. Unfortunately, it looks like a power spike may have taken out the motherboard. I have retired that PC, and came up with a replacement: a linksys wrt54gs router reflashed with DD-WRT firmware and hardware modifications to add a cantenna.

Last week I made a video about putting up the hex beam, and now that I have the video editing software, I made one about the wifi repeater bridge project. Making video is somewhat addictive, so I think there are more on the way. I have a ways to go in terms of production quality – maybe Christmas will bring a better video-capable camera.

On the subject of videos, my home club, the Vienna Wireless Society, is now posting videos of presentations made at the club.