In an earlier post, I described an arduino-based clock that I made for my amateur radio station. I had to interrupt work on it for a business trip, but got back a few days ago. I’m now far enough past jet lag to operate heavy machinery, so I finished mounting the board on an aluminum faceplate and installed it in the station.
Last weekend was Memorial Day in the US, and I spent it with friends camping at Chain Of Lake State Park in Indiana. I lugged along my FT817 and VX8R and Ben (NN9S) also brought some ham equipment including his Arrow-II antenna. The camp site was a short walk from a large field, which afforded a good view of the sky, with a tree lines down around 10 degrees elevation from the far side of the field. We had some help from a couple hams-in-training interested in pinging the ISS with an APRS beacon and in having a voice QSO via Fox1A.
I’ve been meaning to add a clock with multiple time zone display to my radio operating position for a while. The time in UTC is displayed on my computer when I’m logging, but it’s small and it disappears when the screen sleeps. Also, I use the same room to take work-related conference calls, and it would be helpful to have a clock that displays the local time in Madagascar and the time on the US East Coast, where most of my overseas calls are scheduled. The fast, reasonable approach would be to wire up a microprocessor, a real-time clock chip, and an I2C-driven LCD display that could show all three zones at once. However, the only LCDs I have on hand have small fonts and aren’t that bright. On the other hand, I have a bunch of 4-digit x 7-segment LED displays that burn as bright as Sauron atop Barad-dûr. I went with those.
Continuing on the theme of power supplies and related, I thought I would try my hand at making a bench top variable power supply based on a universal laptop adapter. My rationale is that these adapters are made to run on 11-16V, so I could run it off whatever power is available (the 12V bus on my workbench, a battery, from mains by using another power adapter upstream, or even off the car); considering where I live and the reliability of electrical power, this seemed like a good idea. Also, these brick power supplies are, well, built like a brick, and are designed to tolerate abuse.
I originally came across a posting about converting a Kensington model 33197, which seems idea for this purpose because it has two wires for power/ground, and one each for sensing voltage and current that are set by resistors to a fifth wire that carries 5V. Since then, I’ve seen other articles along similar lines.
My plan was to do something similar, but I wanted to add the twist of being able to set a current limit above which power would be entirely cut to the load until reset. I anticipated using a microprocessor and thought the project wouldn’t be to complicated… but that turned out not to be the case. The power adapter is finicky about turning on into loads, doesn’t like being reset, and I haven’t managed to get more than 15W output from it. That said, I now have it working, but its capabilities fall short of what I had anticipated.
It’s been a chicken and egg race for the last couple months – I was working on power supply projects, but at the same time needed an electronic load so I could test the supplies at known current draws. I have had a working electronic load for a few months, but only got around to making it pretty and boxing it up in the last week. The design that I came up with is not very sophisticated, but it uses common parts and it seems pretty solid. The picture at right shows my recently built variable power supply working into the electronic load.
Most of my equipment had the sense to wait until after I had moved from the US to Madagascar to fail, but not this Acer Monitor. I had picked it up cheap as a bundled deal with a desktop computer in 2009 from New Egg Computer, and it failed early in 2014. I had purchased two identical systems at that time, and the other monitor is still working without a problem.
The monitor wasn’t entirely dead – the power LED is still lit up and when power was applied, the word “Acer” would appear for about a second, and then the screen would remain black. This suggested that most of the monitor was working. Since we were packing up for the move, I thought it would be better to box up the monitor and tackle it on the other end after I had a workshop set up. A year and a half later, it came back out of the box.
No, not an article on QRP fox hunts (which I miss, being a bit out of range), but a construction project to make a pair of devices for tracing down wiring. The fox sends a tone down a wire and the hound sniffs around until it finds the right wire by detecting the tone. I found some commercial versions online at a reasonable price, but there isn’t much to these devices, so I figured I should be able to put them together from parts lying around. In what has to be one of the few examples of truth in advertising still to be found on the web, I came across neat circuits for these devices on neatcircuits.com.
The 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.
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).
After winding up some narrow country lanes, this summit is behind a metal metal gate tied shut with rope. A rutted (and at the time muddy) dirt road leads back from the gate towards a cluster of commercial antennas that are on a bit of land only marginally higher than the flat plateau around it. I did walk to that site, but decided that I would do better to work from just across the road where I had parked.
I did not have a lot of time on the way back from Exeter towards London, so I thought I would try my luck on VHF before throwing the HF antenna up over a tree branch. I scrambled up a low wall, held the radio up, and made calls on 2m FM. I got two quick responses from stations about 25 km away and they also worked me on SSB. I continued calling on 2m until I landed my four stations required to make this an official activation. Towards the end, my arm was getting tired, so I rested the bottom of FT817 on my head to the amusement of passing drivers.
I swapped in the FT817’s 6m vertical antenna and tried calling for about 10 minutes, both voice and CW (try working CW with paddles magnetically mounted on the radio which is on top of your head — it is a challenge). No 6m contacts have been logged from the peak, so I was hopeful, but it wasn’t to be.